Answer: between 1000 and 1900

Context: These studies were widely presented as demonstrating that the current warming period is exceptional in comparison to temperatures between 1000 and 1900, and the MBH99 based graph featured in publicity. Even at the draft stage, this finding was disputed by contrarians: in May 2000 Fred Singer's Science and Environmental Policy Project held a press event on Capitol Hill, Washington, D.C., featuring comments on the graph Wibjörn Karlén and Singer argued against the graph at a United States Senate Committee on Commerce, Science and Transportation hearing on 18 July 2000. Contrarian John Lawrence Daly featured a modified version of the IPCC 1990 schematic, which he mis-identified as appearing in the IPCC 1995 report, and argued that "Overturning its own previous view in the 1995 report, the IPCC presented the 'Hockey Stick' as the new orthodoxy with hardly an apology or explanation for the abrupt U-turn since its 1995 report". Criticism of the MBH99 reconstruction in a review paper, which was quickly discredited in the Soon and Baliunas controversy, was picked up by the Bush administration, and a Senate speech by US Republican senator James Inhofe alleged that "manmade global warming is the greatest hoax ever perpetrated on the American people". The data and methodology used to produce the "hockey stick graph" was criticized in papers by Stephen McIntyre and Ross McKitrick, and in turn the criticisms in these papers were examined by other studies and comprehensively refuted by Wahl & Ammann 2007, which showed errors in the methods used by McIntyre and McKitrick.

Question: What range of years was the current warming compared to?


Answer: Fred Singer

Question: Who led the Science and Environmental Policy Project?


Answer: Capitol Hill, Washington, D.C.

Question: Where did Singer hold a press conference in May 2000?


Answer: 18 July 2000

Question: When did Singer dispute the graph at a Senate hearing?


Answer: United States Senate Committee on Commerce, Science and Transportation

Question: What Senate committee did Singer speak to in July 2000?


Answer: Rep. Joe Barton

Context: On 23 June 2005, Rep. Joe Barton, chairman of the House Committee on Energy and Commerce wrote joint letters with Ed Whitfield, Chairman of the Subcommittee on Oversight and Investigations demanding full records on climate research, as well as personal information about their finances and careers, from Mann, Bradley and Hughes. Sherwood Boehlert, chairman of the House Science Committee, said this was a "misguided and illegitimate investigation" apparently aimed at intimidating scientists, and at his request the U.S. National Academy of Sciences arranged for its National Research Council to set up a special investigation. The National Research Council's report agreed that there were some statistical failings, but these had little effect on the graph, which was generally correct. In a 2006 letter to Nature, Mann, Bradley, and Hughes pointed out that their original article had said that "more widespread high-resolution data are needed before more confident conclusions can be reached" and that the uncertainties were "the point of the article".

Question: Who was the chairman of the House Committee on Energy and Commerce?


Answer: Ed Whitfield

Question: Who was Chairman of the Subcommittee on Oversight and Investigations?


Answer: 23 June 2005

Question: When did Barton and Whitfield demand climate research records?


Answer: Sherwood Boehlert

Question: Who was chairman of the House Science Committee?


Answer: Sherwood Boehlert

Question: Who said Barton's investigation was "misguided and illegitimate"?


Answer: 2001

Context: The IPCC Fourth Assessment Report (AR4) published in 2007 featured a graph showing 12 proxy based temperature reconstructions, including the three highlighted in the 2001 Third Assessment Report (TAR); Mann, Bradley & Hughes 1999 as before, Jones et al. 1998 and Briffa 2000 had both been calibrated by newer studies. In addition, analysis of the Medieval Warm Period cited reconstructions by Crowley & Lowery 2000 (as cited in the TAR) and Osborn & Briffa 2006. Ten of these 14 reconstructions covered 1,000 years or longer. Most reconstructions shared some data series, particularly tree ring data, but newer reconstructions used additional data and covered a wider area, using a variety of statistical methods. The section discussed the divergence problem affecting certain tree ring data.

Question: When was the IPCC Third Assessment Report published?


Answer: 2007

Question: When was the IPCC Fourth Assessment Report published?


Answer: Ten

Question: How many Medieval Warm Period reconstructions covered 1,000+ years?


Answer: divergence

Question: What problem did some tree ring data have?


Answer: 14

Question: How many Medieval Warm Period reconstructions were used?


Answer: 1 February 2007

Context: On 1 February 2007, the eve of the publication of IPCC's major report on climate, a study was published suggesting that temperatures and sea levels have been rising at or above the maximum rates proposed during the last IPCC report in 2001. The study compared IPCC 2001 projections on temperature and sea level change with observations. Over the six years studied, the actual temperature rise was near the top end of the range given by IPCC's 2001 projection, and the actual sea level rise was above the top of the range of the IPCC projection.

Question: When was a study published confirming the 2001 IPCC projections?


Answer: temperatures and sea levels have been rising at or above the maximum rates

Question: How did the 2001 IPCC report compare to reality for 2001-2006?


Answer: actual temperature rise was near the top end of the range given

Question: How did the 2001 IPCC report compare to reality on temperature levels?


Answer: actual sea level rise was above the top of the range

Question: How did the 2001 IPCC report compare to reality on sea levels?


Answer: projected rises in sea levels

Context: Another example of scientific research which suggests that previous estimates by the IPCC, far from overstating dangers and risks, have actually understated them is a study on projected rises in sea levels. When the researchers' analysis was "applied to the possible scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC), the researchers found that in 2100 sea levels would be 0.5–1.4 m [50–140 cm] above 1990 levels. These values are much greater than the 9–88 cm as projected by the IPCC itself in its Third Assessment Report, published in 2001". This may have been due, in part, to the expanding human understanding of climate.

Question: What danger did the IPCC understate?


Answer: 9–88 cm

Question: How much did the IPCC Third Assessment Report say sea levels will rise from 1990 to 2100?


Answer: 50–140 cm

Question: How much do researchers now think sea levels will rise from 1990 to 2100?


Answer: 2001

Question: When was the Third Assessment Report published?


Answer: coordinating lead author of the Fifth Assessment Report

Context: Michael Oppenheimer, a long-time participant in the IPCC and coordinating lead author of the Fifth Assessment Report conceded in Science Magazine's State of the Planet 2008-2009 some limitations of the IPCC consensus approach and asks for concurring, smaller assessments of special problems instead of the large scale approach as in the previous IPCC assessment reports. It has become more important to provide a broader exploration of uncertainties. Others see as well mixed blessings of the drive for consensus within the IPCC process and ask to include dissenting or minority positions or to improve statements about uncertainties.

Question: What role did Michael Oppenheimer have in the IPCC's reports?


Answer: Science Magazine

Question: Who published the State of the Planet 2008-2009 report?


Answer: concurring, smaller assessments of special problems

Question: What approach did Oppenheimer advocate?


Answer: the Montreal Protocol

Context: The IPCC process on climate change and its efficiency and success has been compared with dealings with other environmental challenges (compare Ozone depletion and global warming). In case of the Ozone depletion global regulation based on the Montreal Protocol has been successful, in case of Climate Change, the Kyoto Protocol failed. The Ozone case was used to assess the efficiency of the IPCC process. The lockstep situation of the IPCC is having built a broad science consensus while states and governments still follow different, if not opposing goals. The underlying linear model of policy-making of more knowledge we have, the better the political response will be is being doubted.

Question: What has successfully dealt with ozone depletion?


Answer: Climate Change

Question: What did the Kyoto Protocol try to address?


Answer: states and governments

Question: Whose goals often still oppose the IPCC?


Answer: Sheldon Ungar

Context: According to Sheldon Ungar's comparison with global warming, the actors in the ozone depletion case had a better understanding of scientific ignorance and uncertainties. The ozone case communicated to lay persons "with easy-to-understand bridging metaphors derived from the popular culture" and related to "immediate risks with everyday relevance", while the public opinion on climate change sees no imminent danger. The stepwise mitigation of the ozone layer challenge was based as well on successfully reducing regional burden sharing conflicts. In case of the IPCC conclusions and the failure of the Kyoto Protocol, varying regional cost-benefit analysis and burden-sharing conflicts with regard to the distribution of emission reductions remain an unsolved problem. In the UK, a report for a House of Lords committee asked to urge the IPCC to involve better assessments of costs and benefits of climate change but the Stern Review ordered by the UK government made a stronger argument in favor to combat human-made climate change.

Question: Who said people involved in the ozone situation had "a better understanding of scientific ignorance and uncertainties"?


Answer: varying regional cost-benefit analysis and burden-sharing conflicts with regard to the distribution of emission reductions

Question: What remain unsolved problems with the Kyoto Protocol?


Answer: regional burden sharing conflicts

Question: What conflicts did the ozone mitigation reduce?


Answer: the UK government

Question: Who ordered the Stern Review?


Answer: other scientific bodies

Context: Since the IPCC does not carry out its own research, it operates on the basis of scientific papers and independently documented results from other scientific bodies, and its schedule for producing reports requires a deadline for submissions prior to the report's final release. In principle, this means that any significant new evidence or events that change our understanding of climate science between this deadline and publication of an IPCC report cannot be included. In an area of science where our scientific understanding is rapidly changing, this has been raised as a serious shortcoming in a body which is widely regarded as the ultimate authority on the science. However, there has generally been a steady evolution of key findings and levels of scientific confidence from one assessment report to the next.[citation needed]

Question: What does the IPCC rely on for research?


Answer: significant new evidence or events that change our understanding of climate science

Question: What can the IPCC's report deadlines cause to be omitted?


Answer: IPCC

Question: Who is seen as the ultimate climate change authority?


Answer: five

Context: In February 2010, in response to controversies regarding claims in the Fourth Assessment Report, five climate scientists – all contributing or lead IPCC report authors – wrote in the journal Nature calling for changes to the IPCC. They suggested a range of new organizational options, from tightening the selection of lead authors and contributors, to dumping it in favor of a small permanent body, or even turning the whole climate science assessment process into a moderated "living" Wikipedia-IPCC. Other recommendations included that the panel employ a full-time staff and remove government oversight from its processes to avoid political interference.

Question: How many scientists called to change the IPCC in Feb 2010?


Answer: the journal Nature

Question: Where was the Feb 2010 call for change published?


Answer: turning the whole climate science assessment process into a moderated "living" Wikipedia-IPCC

Question: What was one proposal to let the IPCC respond to new evidence faster?


Answer: remove government oversight from its processes

Question: How was it suggested that the IPCC avoid political problems?


Answer: to conduct photosynthesis

Context: Chloroplasts' main role is to conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight and converts it and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water. They then use the ATP and NADPH to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, much amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from 1 in algae up to 100 in plants like Arabidopsis and wheat.

Question: What is the primary purpose of chloroplasts?


Answer: energy

Question: What does ATP store?


Answer: energy

Question: What does NADPH store?


Answer: the Calvin cycle

Question: What is the process of turning CO2 into organic molecules called?


Answer: 1

Question: How many chloroplasts per cell does algae have?


Answer: pinch in two

Context: Chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally pinch in two to reproduce. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts, like mitochondria, contain their own DNA, which is thought to be inherited from their ancestor—a photosynthetic cyanobacterium that was engulfed by an early eukaryotic cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division.

Question: How do chloroplasts reproduce?


Answer: environmental factors like light color and intensity

Question: What influences chloroplasts' behavior?


Answer: contain their own DNA

Question: How are chloroplasts similar to mitochondria?


Answer: a photosynthetic cyanobacterium that was engulfed by an early eukaryotic cell

Question: What was the ancestor of chloroplasts?


Answer: must be inherited by each daughter cell during cell division

Question: How do plants get chloroplasts?


Answer: plants and algae

Context: Chloroplasts are one of many types of organelles in the plant cell. They are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell. Mitochondria are thought to have come from a similar event, where an aerobic prokaryote was engulfed. This origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905 after Andreas Schimper observed in 1883 that chloroplasts closely resemble cyanobacteria. Chloroplasts are only found in plants and algae.

Question: Which organisms have chloroplasts?


Answer: Russian

Question: What nationality was Konstantin Mereschkowski?


Answer: biologist

Question: What was Konstantin Mereschkowski's career?


Answer: 1905

Question: When did Konstantin Mereschkowski suggest the origin of chloroplasts?


Answer: Andreas Schimper

Question: Who said chloroplasts are similar to cyanobacteria?


Answer: Cyanobacteria

Context: Cyanobacteria are considered the ancestors of chloroplasts. They are sometimes called blue-green algae even though they are prokaryotes. They are a diverse phylum of bacteria capable of carrying out photosynthesis, and are gram-negative, meaning that they have two cell membranes. Cyanobacteria also contain a peptidoglycan cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes. Like chloroplasts, they have thylakoids within. On the thylakoid membranes are photosynthetic pigments, including chlorophyll a. Phycobilins are also common cyanobacterial pigments, usually organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though).

Question: What are chloroplasts descended from?


Answer: prokaryotes

Question: What type of organism are cyanobacteria?


Answer: they have two cell membranes

Question: What does 'gram-negative' mean?


Answer: peptidoglycan

Question: What kind of cell wall do cyanobacteria have?


Answer: blue-green algae

Question: How are cyanobacteria sometimes wrongly described?


Answer: eukaryotic

Context: Somewhere around a billion years ago, a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite, but managed to escape the phagocytic vacuole it was contained in. The two innermost lipid-bilayer membranes that surround all chloroplasts correspond to the outer and inner membranes of the ancestral cyanobacterium's gram negative cell wall, and not the phagosomal membrane from the host, which was probably lost. The new cellular resident quickly became an advantage, providing food for the eukaryotic host, which allowed it to live within it. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to the nucleus of the host. Some of its proteins were then synthesized in the cytoplasm of the host cell, and imported back into the chloroplast (formerly the cyanobacterium).

Question: What kind of cell did cynaobacteria enter long ago?


Answer: around a billion years ago

Question: How long ago did cyanobacteria enter a cell?


Answer: two innermost lipid-bilayer membranes

Question: What surrounds chloroplasts?


Answer: phagosomal

Question: What kind of membrane came from the host?


Answer: many of its genes were lost or transferred to the nucleus of the host

Question: What happened when cyanobacteria was assimilated?


Answer: almost the same thing as chloroplast

Context: These chloroplasts, which can be traced back directly to a cyanobacterial ancestor, are known as primary plastids ("plastid" in this context means almost the same thing as chloroplast). All primary chloroplasts belong to one of three chloroplast lineages—the glaucophyte chloroplast lineage, the rhodophyte, or red algal chloroplast lineage, or the chloroplastidan, or green chloroplast lineage. The second two are the largest, and the green chloroplast lineage is the one that contains the land plants.

Question: What does 'plastid' mean?


Answer: three

Question: How many chloroplast lineages are there?


Answer: red algal chloroplast

Question: What does rhodophyte mean?


Answer: green chloroplast

Question: What does chloroplastidan mean?


Answer: the green chloroplast lineage

Question: Which lineage includes land plants?


Answer: glaucophyte

Context: The alga Cyanophora, a glaucophyte, is thought to be one of the first organisms to contain a chloroplast. The glaucophyte chloroplast group is the smallest of the three primary chloroplast lineages, being found in only 13 species, and is thought to be the one that branched off the earliest. Glaucophytes have chloroplasts that retain a peptidoglycan wall between their double membranes, like their cyanobacterial parent. For this reason, glaucophyte chloroplasts are also known as muroplasts. Glaucophyte chloroplasts also contain concentric unstacked thylakoids, which surround a carboxysome - an icosahedral structure that glaucophyte chloroplasts and cyanobacteria keep their carbon fixation enzyme rubisco in. The starch that they synthesize collects outside the chloroplast. Like cyanobacteria, glaucophyte chloroplast thylakoids are studded with light collecting structures called phycobilisomes. For these reasons, glaucophyte chloroplasts are considered a primitive intermediate between cyanobacteria and the more evolved chloroplasts in red algae and plants.

Question: What chloroplast lineage is Cyanophora in?


Answer: alga

Question: What kind of organism is Cyanophora?


Answer: glaucophyte chloroplasts

Question: What are muroplasts?


Answer: a carboxysome

Question: What do concentric unstacked thylakoids surround?


Answer: icosahedral

Question: What kind of structure is a carboxysome?


Answer: chlorophyll a and phycobilins

Context: Rhodoplasts have a double membrane with an intermembrane space and phycobilin pigments organized into phycobilisomes on the thylakoid membranes, preventing their thylakoids from stacking. Some contain pyrenoids. Rhodoplasts have chlorophyll a and phycobilins for photosynthetic pigments; the phycobilin phycoerytherin is responsible for giving many red algae their distinctive red color. However, since they also contain the blue-green chlorophyll a and other pigments, many are reddish to purple from the combination. The red phycoerytherin pigment is an adaptation to help red algae catch more sunlight in deep water—as such, some red algae that live in shallow water have less phycoerytherin in their rhodoplasts, and can appear more greenish. Rhodoplasts synthesize a form of starch called floridean, which collects into granules outside the rhodoplast, in the cytoplasm of the red alga.

Question: What kinds of pigments do rhodoplasts have?


Answer: phycobilisomes

Question: What are rhodoplasts' phycobilin pigments combined into?


Answer: the phycobilin phycoerytherin

Question: What makes red algae red?


Answer: catch more sunlight in deep water

Question: What is the benefit of red algae being red?


Answer: a form of starch

Question: What is floridean?


Answer: phycobilisomes

Context: The chloroplastidan chloroplasts, or green chloroplasts, are another large, highly diverse primary chloroplast lineage. Their host organisms are commonly known as the green algae and land plants. They differ from glaucophyte and red algal chloroplasts in that they have lost their phycobilisomes, and contain chlorophyll b instead. Most green chloroplasts are (obviously) green, though some aren't, like some forms of Hæmatococcus pluvialis, due to accessory pigments that override the chlorophylls' green colors. Chloroplastidan chloroplasts have lost the peptidoglycan wall between their double membrane, and have replaced it with an intermembrane space. Some plants seem to have kept the genes for the synthesis of the peptidoglycan layer, though they've been repurposed for use in chloroplast division instead.

Question: What do red algal chloroplasts have that green chloroplasts don't?


Answer: accessory pigments that override the chlorophylls' green colors

Question: Why aren't some forms of Hæmatococcus pluvialis green?


Answer: the peptidoglycan wall

Question: What don't chloroplastidan chloroplasts have?


Answer: chloroplast division

Question: What have some plants repurposed the peptidoglycan layer genes for?


Answer: chlorophyll b

Question: What do green chloroplasts have instead of phycobilisomes?


Answer: double

Context: While primary chloroplasts have a double membrane from their cyanobacterial ancestor, secondary chloroplasts have additional membranes outside of the original two, as a result of the secondary endosymbiotic event, when a nonphotosynthetic eukaryote engulfed a chloroplast-containing alga but failed to digest it—much like the cyanobacterium at the beginning of this story. The engulfed alga was broken down, leaving only its chloroplast, and sometimes its cell membrane and nucleus, forming a chloroplast with three or four membranes—the two cyanobacterial membranes, sometimes the eaten alga's cell membrane, and the phagosomal vacuole from the host's cell membrane.

Question: What kind of membrane do primary chloroplasts have?


Answer: additional membranes outside of the original two

Question: What differs about secondary chloroplasts' membranes?


Answer: a nonphotosynthetic eukaryote engulfed a chloroplast-containing alga but failed to digest it

Question: What was the secondary endosymbiotic event?


Answer: sometimes the eaten alga's cell membrane, and the phagosomal vacuole from the host's cell membrane

Question: What additional membranes do secondary chloroplasts have?


Answer: its chloroplast, and sometimes its cell membrane and nucleus

Question: What was left when engulfed algae was broken down?


Answer: chloroplasts derived from a green alga

Context: Euglenophytes are a group of common flagellated protists that contain chloroplasts derived from a green alga. Euglenophyte chloroplasts have three membranes—it is thought that the membrane of the primary endosymbiont was lost, leaving the cyanobacterial membranes, and the secondary host's phagosomal membrane. Euglenophyte chloroplasts have a pyrenoid and thylakoids stacked in groups of three. Starch is stored in the form of paramylon, which is contained in membrane-bound granules in the cytoplasm of the euglenophyte.

Question: What kind of chloroplasts do Euglenophytes have?


Answer: common flagellated

Question: What kind of protists are Euglenophytes?


Answer: stacked in groups of three

Question: How are the pyrenoid and thylakoids arranged?


Answer: Starch

Question: What does paramylon store?


Answer: the membrane of the primary endosymbiont

Question: Which membrane was lost in euglenophyte chloroplasts?


Answer: cryptomonads

Context: Cryptophytes, or cryptomonads are a group of algae that contain a red-algal derived chloroplast. Cryptophyte chloroplasts contain a nucleomorph that superficially resembles that of the chlorarachniophytes. Cryptophyte chloroplasts have four membranes, the outermost of which is continuous with the rough endoplasmic reticulum. They synthesize ordinary starch, which is stored in granules found in the periplastid space—outside the original double membrane, in the place that corresponds to the red alga's cytoplasm. Inside cryptophyte chloroplasts is a pyrenoid and thylakoids in stacks of two.

Question: What is another word for cryptophytes?


Answer: red-algal derived chloroplast

Question: What kind of chloroplasts do cryptophytes have?


Answer: nucleomorph

Question: What part of cryptophyte chloroplasts is similar to chlorarachniophytes?


Answer: in granules found in the periplastid space

Question: Where do cryptophyte chloroplasts store starch?


Answer: stacks of two

Question: How do cryptophyte chloroplasts arrange their pyrenoid and thylakoids?


Answer: helicosproidia

Context: Apicomplexans are another group of chromalveolates. Like the helicosproidia, they're parasitic, and have a nonphotosynthetic chloroplast. They were once thought to be related to the helicosproidia, but it is now known that the helicosproida are green algae rather than chromalveolates. The apicomplexans include Plasmodium, the malaria parasite. Many apicomplexans keep a vestigial red algal derived chloroplast called an apicoplast, which they inherited from their ancestors. Other apicomplexans like Cryptosporidium have lost the chloroplast completely. Apicomplexans store their energy in amylopectin starch granules that are located in their cytoplasm, even though they are nonphotosynthetic.

Question: What are Apicomplexans similar to?


Answer: chromalveolates

Question: What are Apicomplexans a type of?


Answer: the malaria parasite

Question: What is Plasmodium?


Answer: a vestigial red algal derived chloroplast

Question: What is an apicoplast?


Answer: in amylopectin starch granules that are located in their cytoplasm

Question: Where do Apicomplexans store energy?


Answer: fatty acids, isopentenyl pyrophosphate, iron-sulfur clusters

Context: Apicoplasts have lost all photosynthetic function, and contain no photosynthetic pigments or true thylakoids. They are bounded by four membranes, but the membranes are not connected to the endoplasmic reticulum. The fact that apicomplexans still keep their nonphotosynthetic chloroplast around demonstrates how the chloroplast carries out important functions other than photosynthesis. Plant chloroplasts provide plant cells with many important things besides sugar, and apicoplasts are no different—they synthesize fatty acids, isopentenyl pyrophosphate, iron-sulfur clusters, and carry out part of the heme pathway. This makes the apicoplast an attractive target for drugs to cure apicomplexan-related diseases. The most important apicoplast function is isopentenyl pyrophosphate synthesis—in fact, apicomplexans die when something interferes with this apicoplast function, and when apicomplexans are grown in an isopentenyl pyrophosphate-rich medium, they dump the organelle.

Question: What do apicoplasts synthesize?


Answer: apicomplexan-related diseases

Question: What kind of diseases do drugs target apicoplasts for?


Answer: isopentenyl pyrophosphate synthesis

Question: What is the most important thing apicoplasts do?


Answer: photosynthetic pigments or true thylakoids

Question: What are apicoplasts missing?


Answer: four

Question: How many membranes do apicoplasts have?


Answer: Peridinin

Context: The most common dinophyte chloroplast is the peridinin-type chloroplast, characterized by the carotenoid pigment peridinin in their chloroplasts, along with chlorophyll a and chlorophyll c2. Peridinin is not found in any other group of chloroplasts. The peridinin chloroplast is bounded by three membranes (occasionally two), having lost the red algal endosymbiont's original cell membrane. The outermost membrane is not connected to the endoplasmic reticulum. They contain a pyrenoid, and have triplet-stacked thylakoids. Starch is found outside the chloroplast An important feature of these chloroplasts is that their chloroplast DNA is highly reduced and fragmented into many small circles. Most of the genome has migrated to the nucleus, and only critical photosynthesis-related genes remain in the chloroplast.

Question: What is only found in peridinin-type chloroplasts?


Answer: peridinin-type chloroplast

Question: Where is Peridinin found?


Answer: triplet-stacked

Question: How are peridinin-type chloroplasts' thylakoids arranged?


Answer: the red algal endosymbiont's original cell membrane

Question: What have peridinin-type chloroplasts lost?


Answer: fucoxanthin dinophyte

Context: The fucoxanthin dinophyte lineages (including Karlodinium and Karenia) lost their original red algal derived chloroplast, and replaced it with a new chloroplast derived from a haptophyte endosymbiont. Karlodinium and Karenia probably took up different heterokontophytes. Because the haptophyte chloroplast has four membranes, tertiary endosymbiosis would be expected to create a six membraned chloroplast, adding the haptophyte's cell membrane and the dinophyte's phagosomal vacuole. However, the haptophyte was heavily reduced, stripped of a few membranes and its nucleus, leaving only its chloroplast (with its original double membrane), and possibly one or two additional membranes around it.

Question: What lineage is Karlodinium in?


Answer: fucoxanthin dinophyte

Question: What lineage is Karenia in?


Answer: four

Question: How many membranes does the haptophyte chloroplast have?


Answer: a six membraned chloroplast

Question: What is tertiary endosymbiosis of haptophyte chloroplasts expected to create?


Answer: a cryptophyte

Context: Members of the genus Dinophysis have a phycobilin-containing chloroplast taken from a cryptophyte. However, the cryptophyte is not an endosymbiont—only the chloroplast seems to have been taken, and the chloroplast has been stripped of its nucleomorph and outermost two membranes, leaving just a two-membraned chloroplast. Cryptophyte chloroplasts require their nucleomorph to maintain themselves, and Dinophysis species grown in cell culture alone cannot survive, so it is possible (but not confirmed) that the Dinophysis chloroplast is a kleptoplast—if so, Dinophysis chloroplasts wear out and Dinophysis species must continually engulf cryptophytes to obtain new chloroplasts to replace the old ones.

Question: Where did Dinophysis get its chloroplasts from?


Answer: its nucleomorph and outermost two membranes

Question: What have the Dinophysis chloroplasts lost?


Answer: a phycobilin-containing chloroplast

Question: What is the chloroplast of Dinophysis?


Answer: a two-membraned chloroplast

Question: What is left of the Dinophysis chloroplasts?


Answer: heterokontophyte

Context: Some dinophytes, like Kryptoperidinium and Durinskia have a diatom (heterokontophyte) derived chloroplast. These chloroplasts are bounded by up to five membranes, (depending on whether you count the entire diatom endosymbiont as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original mitochondria, and has endoplasmic reticulum, ribosomes, a nucleus, and of course, red algal derived chloroplasts—practically a complete cell, all inside the host's endoplasmic reticulum lumen. However the diatom endosymbiont can't store its own food—its starch is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a nucleomorph because it shows no sign of genome reduction, and might have even been expanded. Diatoms have been engulfed by dinoflagellates at least three times.

Question: What is another word for diatom?


Answer: a diatom (heterokontophyte) derived chloroplast

Question: What is Durinskia's chloroplast?


Answer: up to five

Question: How many membranes does Durinskia's chloroplast have?


Answer: the entire diatom endosymbiont as the chloroplast

Question: What is sometimes but not always counted regarding Durinskia's chloroplast membranes?


Answer: granules in the dinophyte host's cytoplasm

Question: Where does the diatom endosymbiont store starch?


Answer: the dinophyte nucleus

Context: Lepidodinium viride and its close relatives are dinophytes that lost their original peridinin chloroplast and replaced it with a green algal derived chloroplast (more specifically, a prasinophyte). Lepidodinium is the only dinophyte that has a chloroplast that's not from the rhodoplast lineage. The chloroplast is surrounded by two membranes and has no nucleomorph—all the nucleomorph genes have been transferred to the dinophyte nucleus. The endosymbiotic event that led to this chloroplast was serial secondary endosymbiosis rather than tertiary endosymbiosis—the endosymbiont was a green alga containing a primary chloroplast (making a secondary chloroplast).

Question: Where do nucleomorph genes transfer to?


Answer: Lepidodinium

Question: What is the only dinophyte that has a non-rhodoplast chloroplast?


Answer: their original peridinin chloroplast

Question: What did Lepidodinium viride lose?


Answer: a green algal derived chloroplast

Question: What did Lepidodinium viride replace their original chloroplast with?


Answer: a green algal derived chloroplast

Question: What is a prasinophyte?


Answer: first set of endosymbiotic events

Context: While most chloroplasts originate from that first set of endosymbiotic events, Paulinella chromatophora is an exception that acquired a photosynthetic cyanobacterial endosymbiont more recently. It is not clear whether that symbiont is closely related to the ancestral chloroplast of other eukaryotes. Being in the early stages of endosymbiosis, Paulinella chromatophora can offer some insights into how chloroplasts evolved. Paulinella cells contain one or two sausage shaped blue-green photosynthesizing structures called chromatophores, descended from the cyanobacterium Synechococcus. Chromatophores cannot survive outside their host. Chromatophore DNA is about a million base pairs long, containing around 850 protein encoding genes—far less than the three million base pair Synechococcus genome, but much larger than the approximately 150,000 base pair genome of the more assimilated chloroplast. Chromatophores have transferred much less of their DNA to the nucleus of their host. About 0.3–0.8% of the nuclear DNA in Paulinella is from the chromatophore, compared with 11–14% from the chloroplast in plants.

Question: Where did most chloroplasts come from?


Answer: acquired a photosynthetic cyanobacterial endosymbiont more recently

Question: What is different about Paulinella chromatophora?


Answer: about a million

Question: How many base pairs are there in Chromatophore DNA?


Answer: around 850

Question: How many protein-encoding genes are there in Chromatophore DNA?


Answer: three million

Question: How many base pairs are there in Synechococcus DNA?


Answer: ctDNA, or cpDNA

Context: Chloroplasts have their own DNA, often abbreviated as ctDNA, or cpDNA. It is also known as the plastome. Its existence was first proved in 1962, and first sequenced in 1986—when two Japanese research teams sequenced the chloroplast DNA of liverwort and tobacco. Since then, hundreds of chloroplast DNAs from various species have been sequenced, but they're mostly those of land plants and green algae—glaucophytes, red algae, and other algal groups are extremely underrepresented, potentially introducing some bias in views of "typical" chloroplast DNA structure and content.

Question: What is chloroplast DNA abbreviated as?


Answer: the plastome

Question: What is a synonym for chloroplast DNA?


Answer: 1962

Question: When was the plastome discovered?


Answer: 1986

Question: When was the first plastome sequenced?


Answer: two Japanese research teams

Question: Who sequenced the first plastome?


Answer: The inverted repeat regions

Context: The inverted repeat regions are highly conserved among land plants, and accumulate few mutations. Similar inverted repeats exist in the genomes of cyanobacteria and the other two chloroplast lineages (glaucophyta and rhodophyceæ), suggesting that they predate the chloroplast, though some chloroplast DNAs have since lost or flipped the inverted repeats (making them direct repeats). It is possible that the inverted repeats help stabilize the rest of the chloroplast genome, as chloroplast DNAs which have lost some of the inverted repeat segments tend to get rearranged more.

Question: What seldom mutates?


Answer: direct repeats

Question: What have some inverted repeats become?


Answer: stabilize the rest of the chloroplast genome

Question: What could inverted repeats help do?


Answer: electron microscopy

Context: The mechanism for chloroplast DNA (cpDNA) replication has not been conclusively determined, but two main models have been proposed. Scientists have attempted to observe chloroplast replication via electron microscopy since the 1970s. The results of the microscopy experiments led to the idea that chloroplast DNA replicates using a double displacement loop (D-loop). As the D-loop moves through the circular DNA, it adopts a theta intermediary form, also known as a Cairns replication intermediate, and completes replication with a rolling circle mechanism. Transcription starts at specific points of origin. Multiple replication forks open up, allowing replication machinery to transcribe the DNA. As replication continues, the forks grow and eventually converge. The new cpDNA structures separate, creating daughter cpDNA chromosomes.

Question: How is chloroplast replication observed?


Answer: two

Question: How many major chloroplast replication models have been suggested?


Answer: a theta intermediary form

Question: What is a Cairns replication intermediate?


Answer: a Cairns replication intermediate

Question: What is a D-loop?


Answer: with a rolling circle mechanism

Question: How does the D-loop finish replicating?


Answer: A → G deamination

Context: In cpDNA, there are several A → G deamination gradients. DNA becomes susceptible to deamination events when it is single stranded. When replication forks form, the strand not being copied is single stranded, and thus at risk for A → G deamination. Therefore, gradients in deamination indicate that replication forks were most likely present and the direction that they initially opened (the highest gradient is most likely nearest the start site because it was single stranded for the longest amount of time). This mechanism is still the leading theory today; however, a second theory suggests that most cpDNA is actually linear and replicates through homologous recombination. It further contends that only a minority of the genetic material is kept in circular chromosomes while the rest is in branched, linear, or other complex structures.

Question: What kind of gradients does cpDNA have?


Answer: when it is single stranded

Question: What makes DNA vulnerable to deamination?


Answer: linear

Question: How does the secondary theory say most cpDNA is structured?


Answer: homologous recombination

Question: How does the secondary theory say most cpDNA replicates?


Answer: in branched, linear, or other complex structures

Question: Where does the secondary theory say most genes are kept?


Answer: bacteriophage T4

Context: One of competing model for cpDNA replication asserts that most cpDNA is linear and participates in homologous recombination and replication structures similar to bacteriophage T4. It has been established that some plants have linear cpDNA, such as maize, and that more species still contain complex structures that scientists do not yet understand. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not expand the multiple A --> G gradients seen in plastomes. Because of the failure to explain the deamination gradient as well as the numerous plant species that have been shown to have circular cpDNA, the predominant theory continues to hold that most cpDNA is circular and most likely replicates via a D loop mechanism.

Question: What is cpDNA's replication similar to?


Answer: linear

Question: What kind of cpDNA does maize have?


Answer: circular

Question: How is most plants' cpDNA arranged?


Answer: via a D loop mechanism

Question: How does most plants' cpDNA replicate?


Answer: Endosymbiotic gene transfer

Context: Endosymbiotic gene transfer is how we know about the lost chloroplasts in many chromalveolate lineages. Even if a chloroplast is eventually lost, the genes it donated to the former host's nucleus persist, providing evidence for the lost chloroplast's existence. For example, while diatoms (a heterokontophyte) now have a red algal derived chloroplast, the presence of many green algal genes in the diatom nucleus provide evidence that the diatom ancestor (probably the ancestor of all chromalveolates too) had a green algal derived chloroplast at some point, which was subsequently replaced by the red chloroplast.

Question: What shows us lost chloroplasts?


Answer: the lost chloroplast's existence

Question: What do donated genes give evidence of?


Answer: a red algal derived chloroplast

Question: What kind of chloroplasts do diatoms have?


Answer: green algal derived chloroplast

Question: What kind of chloroplasts did diatoms have but lost?


Answer: nonfunctional pseudogenes

Context: Curiously, around half of the protein products of transferred genes aren't even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway (though it should be noted that many secondary plastids are bounded by an outermost membrane derived from the host's cell membrane, and therefore topologically outside of the cell, because to reach the chloroplast from the cytosol, you have to cross the cell membrane, just like if you were headed for the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway).

Question: What is the status of most chloroplast genes in the mitochondrion?


Answer: around half

Question: How much of the protein products of transferred genes don't go back to chloroplasts?


Answer: participating in cell division, protein routing, and even disease resistance

Question: What new tasks do the protein products of transferred genes take on?


Answer: the cell membrane

Question: What do you have to cross to reach the chloroplast in many secondary plastids?


Answer: a ribosome

Context: After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, an enzyme specific to chloroplast proteins phosphorylates, or adds a phosphate group to many (but not all) of them in their transit sequences. Phosphorylation helps many proteins bind the polypeptide, keeping it from folding prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the cytosol. At the same time, they have to keep just enough shape so that they can be recognized by the chloroplast. These proteins also help the polypeptide get imported into the chloroplast.

Question: What is the chloroplast polypeptide synthesized on?


Answer: in the cytosol

Question: Where is the chloroplast polypeptide synthesized?


Answer: helps many proteins bind the polypeptide

Question: What does Phosphorylation do?


Answer: keeping it from folding prematurely

Question: What is the benefit of polypeptide binding?


Answer: lens-shaped

Context: In land plants, chloroplasts are generally lens-shaped, 5–8 μm in diameter and 1–3 μm thick. Greater diversity in chloroplast shapes exists among the algae, which often contain a single chloroplast that can be shaped like a net (e.g., Oedogonium), a cup (e.g., Chlamydomonas), a ribbon-like spiral around the edges of the cell (e.g., Spirogyra), or slightly twisted bands at the cell edges (e.g., Sirogonium). Some algae have two chloroplasts in each cell; they are star-shaped in Zygnema, or may follow the shape of half the cell in order Desmidiales. In some algae, the chloroplast takes up most of the cell, with pockets for the nucleus and other organelles (for example some species of Chlorella have a cup-shaped chloroplast that occupies much of the cell).

Question: How are chloroplasts in land plants usually shaped?


Answer: 5–8 μm in diameter

Question: How large across are chloroplasts in land plants?


Answer: 1–3 μm

Question: How thick are chloroplasts in land plants?


Answer: a net

Question: What shape is Oedogonium's chloroplasts?


Answer: a cup

Question: What shape is Chlamydomonas's chloroplasts?


Answer: a double membrane

Context: There are some common misconceptions about the outer and inner chloroplast membranes. The fact that chloroplasts are surrounded by a double membrane is often cited as evidence that they are the descendants of endosymbiotic cyanobacteria. This is often interpreted as meaning the outer chloroplast membrane is the product of the host's cell membrane infolding to form a vesicle to surround the ancestral cyanobacterium—which is not true—both chloroplast membranes are homologous to the cyanobacterium's original double membranes.

Question: What is evidence chloroplasts descended from endosymbiotic cyanobacteria?


Answer: the product of the host's cell membrane infolding to form a vesicle to surround the ancestral cyanobacterium

Question: What is incorrectly thought about the outer chloroplast membrane?


Answer: homologous

Question: How do both chloroplast membranes compare to cyanobacterium's original double membranes?


Answer: the mitochondrial double membrane

Context: The chloroplast double membrane is also often compared to the mitochondrial double membrane. This is not a valid comparison—the inner mitochondria membrane is used to run proton pumps and carry out oxidative phosphorylation across to generate ATP energy. The only chloroplast structure that can considered analogous to it is the internal thylakoid system. Even so, in terms of "in-out", the direction of chloroplast H+ ion flow is in the opposite direction compared to oxidative phosphorylation in mitochondria. In addition, in terms of function, the inner chloroplast membrane, which regulates metabolite passage and synthesizes some materials, has no counterpart in the mitochondrion.

Question: What is the chloroplast double membrane sometimes compared to?


Answer: run proton pumps and carry out oxidative phosphorylation

Question: What does the inner mitochondria membrane do?


Answer: generate ATP energy

Question: What does oxidative phosphorylation do?


Answer: the internal thylakoid system

Question: What chloroplast structure is similar to the inner mitochondria membrane?


Answer: the inner chloroplast membrane

Question: What part of chloroplasts isn't similar to mitochondria?


Answer: Stromules

Context: The chloroplast membranes sometimes protrude out into the cytoplasm, forming a stromule, or stroma-containing tubule. Stromules are very rare in chloroplasts, and are much more common in other plastids like chromoplasts and amyloplasts in petals and roots, respectively. They may exist to increase the chloroplast's surface area for cross-membrane transport, because they are often branched and tangled with the endoplasmic reticulum. When they were first observed in 1962, some plant biologists dismissed the structures as artifactual, claiming that stromules were just oddly shaped chloroplasts with constricted regions or dividing chloroplasts. However, there is a growing body of evidence that stromules are functional, integral features of plant cell plastids, not merely artifacts.

Question: What are more common in other plastids than chloroplasts?


Answer: stroma-containing tubule

Question: What is a stromule?


Answer: to increase the chloroplast's surface area for cross-membrane transport

Question: Why do stromules exist?


Answer: 1962

Question: When were stromules discovered?


Answer: in the chloroplasts of C4 plants

Context: Some chloroplasts contain a structure called the chloroplast peripheral reticulum. It is often found in the chloroplasts of C4 plants, though it has also been found in some C3 angiosperms, and even some gymnosperms. The chloroplast peripheral reticulum consists of a maze of membranous tubes and vesicles continuous with the inner chloroplast membrane that extends into the internal stromal fluid of the chloroplast. Its purpose is thought to be to increase the chloroplast's surface area for cross-membrane transport between its stroma and the cell cytoplasm. The small vesicles sometimes observed may serve as transport vesicles to shuttle stuff between the thylakoids and intermembrane space.

Question: Where is the chloroplast peripheral reticulum usually found?


Answer: in some C3 angiosperms, and even some gymnosperms

Question: Where is the chloroplast peripheral reticulum less commonly found?


Answer: The chloroplast peripheral reticulum

Question: What is a maze of membranous tubes?


Answer: increase the chloroplast's surface area for cross-membrane transport

Question: What does the chloroplast peripheral reticulum do?


Answer: the thylakoids and intermembrane space

Question: Where do transport vesicles move between?


Answer: synthesize a small fraction of their proteins

Context: Chloroplasts have their own ribosomes, which they use to synthesize a small fraction of their proteins. Chloroplast ribosomes are about two-thirds the size of cytoplasmic ribosomes (around 17 nm vs 25 nm). They take mRNAs transcribed from the chloroplast DNA and translate them into protein. While similar to bacterial ribosomes, chloroplast translation is more complex than in bacteria, so chloroplast ribosomes include some chloroplast-unique features. Small subunit ribosomal RNAs in several Chlorophyta and euglenid chloroplasts lack motifs for shine-dalgarno sequence recognition, which is considered essential for translation initiation in most chloroplasts and prokaryotes. Such loss is also rarely observed in other plastids and prokaryotes.

Question: What do chloroplasts use their ribosomes for?


Answer: 17 nm

Question: How large are Chloroplast ribosomes?


Answer: 25 nm

Question: How large are Cytoplasmic ribosomes?


Answer: motifs for shine-dalgarno sequence recognition

Question: What are some Chlorophyta and euglenid chloroplasts missing?


Answer: is considered essential for translation initiation in most chloroplasts and prokaryotes

Question: Why is shine-dalgarno sequence recognition important?


Answer: plastoglobulus, sometimes spelled plastoglobule(s)

Context: Plastoglobuli (singular plastoglobulus, sometimes spelled plastoglobule(s)), are spherical bubbles of lipids and proteins about 45–60 nanometers across. They are surrounded by a lipid monolayer. Plastoglobuli are found in all chloroplasts, but become more common when the chloroplast is under oxidative stress, or when it ages and transitions into a gerontoplast. Plastoglobuli also exhibit a greater size variation under these conditions. They are also common in etioplasts, but decrease in number as the etioplasts mature into chloroplasts.

Question: What is a single Plastoglobuli called?


Answer: spherical bubbles

Question: What shape are Plastoglobuli?


Answer: lipids and proteins

Question: What are Plastoglobuli made of?


Answer: 45–60 nanometers across

Question: How large are Plastoglobuli?


Answer: a lipid monolayer

Question: What surrounds Plastoglobuli?


Answer: either to a thylakoid or to another plastoglobulus attached to a thylakoid

Context: Plastoglobuli were once thought to be free-floating in the stroma, but it is now thought that they are permanently attached either to a thylakoid or to another plastoglobulus attached to a thylakoid, a configuration that allows a plastoglobulus to exchange its contents with the thylakoid network. In normal green chloroplasts, the vast majority of plastoglobuli occur singularly, attached directly to their parent thylakoid. In old or stressed chloroplasts, plastoglobuli tend to occur in linked groups or chains, still always anchored to a thylakoid.

Question: What are Plastoglobuli attached to?


Answer: the thylakoid network

Question: What do Plastoglobuli exchange contents with?


Answer: singularly, attached directly to their parent thylakoid

Question: How are green chloroplasts' Plastoglobuli arranged?


Answer: In old or stressed chloroplasts

Question: When do Plastoglobuli occur in linked groups?


Answer: The chloroplasts of some hornworts and algae

Context: The chloroplasts of some hornworts and algae contain structures called pyrenoids. They are not found in higher plants. Pyrenoids are roughly spherical and highly refractive bodies which are a site of starch accumulation in plants that contain them. They consist of a matrix opaque to electrons, surrounded by two hemispherical starch plates. The starch is accumulated as the pyrenoids mature. In algae with carbon concentrating mechanisms, the enzyme rubisco is found in the pyrenoids. Starch can also accumulate around the pyrenoids when CO2 is scarce. Pyrenoids can divide to form new pyrenoids, or be produced "de novo".

Question: Where are pyrenoids found?


Answer: roughly spherical

Question: What shape are pyrenoids?


Answer: highly refractive

Question: What do pyrenoids look like?


Answer: starch

Question: What do pyrenoids store?


Answer: divide to form new pyrenoids, or be produced "de novo"

Question: How can pyrenoids replicate?


Answer: the helical thylakoid model

Context: In the helical thylakoid model, grana consist of a stack of flattened circular granal thylakoids that resemble pancakes. Each granum can contain anywhere from two to a hundred thylakoids, though grana with 10–20 thylakoids are most common. Wrapped around the grana are helicoid stromal thylakoids, also known as frets or lamellar thylakoids. The helices ascend at an angle of 20–25°, connecting to each granal thylakoid at a bridge-like slit junction. The helicoids may extend as large sheets that link multiple grana, or narrow to tube-like bridges between grana. While different parts of the thylakoid system contain different membrane proteins, the thylakoid membranes are continuous and the thylakoid space they enclose form a single continuous labyrinth.

Question: In what model do grana look like pancakes?


Answer: flattened circular

Question: What shape are granal thylakoids?


Answer: anywhere from two to a hundred

Question: How many granal thylakoids can be in each granum?


Answer: 10–20

Question: How many granal thylakoids are usually in each granum?


Answer: helicoid stromal thylakoids

Question: What are frets?


Answer: light energy

Context: Embedded in the thylakoid membranes are important protein complexes which carry out the light reactions of photosynthesis. Photosystem II and photosystem I contain light-harvesting complexes with chlorophyll and carotenoids that absorb light energy and use it to energize electrons. Molecules in the thylakoid membrane use the energized electrons to pump hydrogen ions into the thylakoid space, decreasing the pH and turning it acidic. ATP synthase is a large protein complex that harnesses the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy as the hydrogen ions flow back out into the stroma—much like a dam turbine.

Question: What does chlorophyll absorb?


Answer: light energy

Question: What do carotenoids absorb?


Answer: energize electrons

Question: What does chlorophyll use light energy to do?


Answer: pump hydrogen ions into the thylakoid space

Question: What does the thylakoid membrane use the energized electrons for?


Answer: a dam turbine

Question: What is ATP synthase similar to?


Answer: two

Context: There are two types of thylakoids—granal thylakoids, which are arranged in grana, and stromal thylakoids, which are in contact with the stroma. Granal thylakoids are pancake-shaped circular disks about 300–600 nanometers in diameter. Stromal thylakoids are helicoid sheets that spiral around grana. The flat tops and bottoms of granal thylakoids contain only the relatively flat photosystem II protein complex. This allows them to stack tightly, forming grana with many layers of tightly appressed membrane, called granal membrane, increasing stability and surface area for light capture.

Question: How many types of thylakoids are there?


Answer: are arranged in grana

Question: What distinguishes granal thylakoids?


Answer: are in contact with the stroma

Question: What distinguishes stromal thylakoids?


Answer: pancake-shaped circular disks

Question: What shape are granal thylakoids?


Answer: about 300–600 nanometers in diameter

Question: How large are granal thylakoids?


Answer: about thirty

Context: In addition to chlorophylls, another group of yellow–orange pigments called carotenoids are also found in the photosystems. There are about thirty photosynthetic carotenoids. They help transfer and dissipate excess energy, and their bright colors sometimes override the chlorophyll green, like during the fall, when the leaves of some land plants change color. β-carotene is a bright red-orange carotenoid found in nearly all chloroplasts, like chlorophyll a. Xanthophylls, especially the orange-red zeaxanthin, are also common. Many other forms of carotenoids exist that are only found in certain groups of chloroplasts.

Question: How many photosynthetic carotenoids are there?


Answer: help transfer and dissipate excess energy

Question: What do photosynthetic carotenoids do?


Answer: their bright colors sometimes override the chlorophyll green

Question: Why do carotenoids make leaves change color in the fall?


Answer: a bright red-orange carotenoid

Question: What is beta carotene?


Answer: orange-red zeaxanthin

Question: What is the most common Xanthophyll?


Answer: e a third group of pigments found in cyanobacteria

Context: Phycobilins are a third group of pigments found in cyanobacteria, and glaucophyte, red algal, and cryptophyte chloroplasts. Phycobilins come in all colors, though phycoerytherin is one of the pigments that makes many red algae red. Phycobilins often organize into relatively large protein complexes about 40 nanometers across called phycobilisomes. Like photosystem I and ATP synthase, phycobilisomes jut into the stroma, preventing thylakoid stacking in red algal chloroplasts. Cryptophyte chloroplasts and some cyanobacteria don't have their phycobilin pigments organized into phycobilisomes, and keep them in their thylakoid space instead.

Question: What are Phycobilins?


Answer: red

Question: What color is phycoerytherin?


Answer: red algae

Question: What does phycoerytherin appear in?


Answer: relatively large protein complexes

Question: What are phycobilisomes?


Answer: about 40 nanometers across

Question: How big are phycobilisomes?


Answer: an enzyme called rubisco

Context: To fix carbon dioxide into sugar molecules in the process of photosynthesis, chloroplasts use an enzyme called rubisco. Rubisco has a problem—it has trouble distinguishing between carbon dioxide and oxygen, so at high oxygen concentrations, rubisco starts accidentally adding oxygen to sugar precursors. This has the end result of ATP energy being wasted and CO2 being released, all with no sugar being produced. This is a big problem, since O2 is produced by the initial light reactions of photosynthesis, causing issues down the line in the Calvin cycle which uses rubisco.

Question: What do chloroplasts use to fix carbon dioxide into sugar?


Answer: it has trouble distinguishing between carbon dioxide and oxygen

Question: What is rubisco's flaw?


Answer: at high oxygen concentrations, rubisco starts accidentally adding oxygen to sugar precursors

Question: What effect does rubisco's flaw have?


Answer: the Calvin cycle

Question: What process down the line does rubisco's flaw interfere with?


Answer: ATP energy

Question: What is wasted by rubisco's flaw?


Answer: light reactions

Context: As a result, chloroplasts in C4 mesophyll cells and bundle sheath cells are specialized for each stage of photosynthesis. In mesophyll cells, chloroplasts are specialized for the light reactions, so they lack rubisco, and have normal grana and thylakoids, which they use to make ATP and NADPH, as well as oxygen. They store CO2 in a four-carbon compound, which is why the process is called C4 photosynthesis. The four-carbon compound is then transported to the bundle sheath chloroplasts, where it drops off CO2 and returns to the mesophyll. Bundle sheath chloroplasts do not carry out the light reactions, preventing oxygen from building up in them and disrupting rubisco activity. Because of this, they lack thylakoids organized into grana stacks—though bundle sheath chloroplasts still have free-floating thylakoids in the stroma where they still carry out cyclic electron flow, a light-driven method of synthesizing ATP to power the Calvin cycle without generating oxygen. They lack photosystem II, and only have photosystem I—the only protein complex needed for cyclic electron flow. Because the job of bundle sheath chloroplasts is to carry out the Calvin cycle and make sugar, they often contain large starch grains.

Question: What are chloroplasts in mesophyll cells specialized for?


Answer: rubisco

Question: What do chloroplasts in mesophyll cells lack?


Answer: normal grana and thylakoids

Question: What do chloroplasts in mesophyll cells specialized use to make ATP?


Answer: a four-carbon compound

Question: What do chloroplasts in mesophyll cells store carbon dioxide in?


Answer: to carry out the Calvin cycle and make sugar

Question: What do bundle sheath chloroplasts specialize in?


Answer: All green parts

Context: Not all cells in a multicellular plant contain chloroplasts. All green parts of a plant contain chloroplasts—the chloroplasts, or more specifically, the chlorophyll in them are what make the photosynthetic parts of a plant green. The plant cells which contain chloroplasts are usually parenchyma cells, though chloroplasts can also be found in collenchyma tissue. A plant cell which contains chloroplasts is known as a chlorenchyma cell. A typical chlorenchyma cell of a land plant contains about 10 to 100 chloroplasts.

Question: What parts of plants have chloroplasts?


Answer: the chlorophyll in them

Question: What makes plants green?


Answer: parenchyma cells

Question: What plant cells have chloroplasts in them?


Answer: collenchyma tissue

Question: Where can chloroplasts sometimes be found?


Answer: A plant cell which contains chloroplasts

Question: What is a chlorenchyma cell?


Answer: in the stems

Context: In some plants such as cacti, chloroplasts are found in the stems, though in most plants, chloroplasts are concentrated in the leaves. One square millimeter of leaf tissue can contain half a million chloroplasts. Within a leaf, chloroplasts are mainly found in the mesophyll layers of a leaf, and the guard cells of stomata. Palisade mesophyll cells can contain 30–70 chloroplasts per cell, while stomatal guard cells contain only around 8–15 per cell, as well as much less chlorophyll. Chloroplasts can also be found in the bundle sheath cells of a leaf, especially in C4 plants, which carry out the Calvin cycle in their bundle sheath cells. They are often absent from the epidermis of a leaf.

Question: Where do cacti have chloroplasts?


Answer: concentrated in the leaves

Question: Where do most plants have chloroplasts?


Answer: 8–15 per cell

Question: How many chloroplasts are in stomatal guard cells?


Answer: half a million

Question: How many chloroplasts are in a square mm of a leaf?


Answer: the mesophyll layers

Question: What layers of a leaf have chloroplasts?


Answer: low-light conditions

Context: The chloroplasts of plant and algal cells can orient themselves to best suit the available light. In low-light conditions, they will spread out in a sheet—maximizing the surface area to absorb light. Under intense light, they will seek shelter by aligning in vertical columns along the plant cell's cell wall or turning sideways so that light strikes them edge-on. This reduces exposure and protects them from photooxidative damage. This ability to distribute chloroplasts so that they can take shelter behind each other or spread out may be the reason why land plants evolved to have many small chloroplasts instead of a few big ones. Chloroplast movement is considered one of the most closely regulated stimulus-response systems that can be found in plants. Mitochondria have also been observed to follow chloroplasts as they move.

Question: When do chloroplasts spread out flat?


Answer: Under intense light

Question: When do chloroplasts arrange in vertical columns or turn sideways?


Answer: photooxidative damage

Question: What does turning sideways protect chloroplasts from?


Answer: to distribute chloroplasts so that they can take shelter behind each other or spread out

Question: Why do land plants have more and smaller chloroplasts?


Answer: Mitochondria

Question: What sometimes follows moving chloroplasts?


Answer: two

Context: Plants have two main immune responses—the hypersensitive response, in which infected cells seal themselves off and undergo programmed cell death, and systemic acquired resistance, where infected cells release signals warning the rest of the plant of a pathogen's presence. Chloroplasts stimulate both responses by purposely damaging their photosynthetic system, producing reactive oxygen species. High levels of reactive oxygen species will cause the hypersensitive response. The reactive oxygen species also directly kill any pathogens within the cell. Lower levels of reactive oxygen species initiate systemic acquired resistance, triggering defense-molecule production in the rest of the plant.

Question: How many major immune responses do plants have?


Answer: infected cells seal themselves off and undergo programmed cell death

Question: What is the hypersensitive response of a plant immune system?


Answer: infected cells release signals warning the rest of the plant of a pathogen's presence

Question: What is the systemic acquired resistance response of a plant immune system?


Answer: by purposely damaging their photosynthetic system

Question: How do chloroplasts trigger the plant's immune system?


Answer: reactive oxygen species

Question: What does damaging photosynthesis systems create?


Answer: salicylic acid, jasmonic acid, nitric oxide and reactive oxygen species

Context: Chloroplasts can serve as cellular sensors. After detecting stress in a cell, which might be due to a pathogen, chloroplasts begin producing molecules like salicylic acid, jasmonic acid, nitric oxide and reactive oxygen species which can serve as defense-signals. As cellular signals, reactive oxygen species are unstable molecules, so they probably don't leave the chloroplast, but instead pass on their signal to an unknown second messenger molecule. All these molecules initiate retrograde signaling—signals from the chloroplast that regulate gene expression in the nucleus.

Question: What molecules act as defense signals?


Answer: After detecting stress in a cell

Question: When do chloroplasts produce defense signals?


Answer: pass on their signal to an unknown second messenger molecule

Question: What happens to reactive oxygen species signals since they don't leave the chloroplast?


Answer: signals from the chloroplast that regulate gene expression in the nucleus

Question: What is retrograde signaling?


Answer: photosynthesis

Context: One of the main functions of the chloroplast is its role in photosynthesis, the process by which light is transformed into chemical energy, to subsequently produce food in the form of sugars. Water (H2O) and carbon dioxide (CO2) are used in photosynthesis, and sugar and oxygen (O2) is made, using light energy. Photosynthesis is divided into two stages—the light reactions, where water is split to produce oxygen, and the dark reactions, or Calvin cycle, which builds sugar molecules from carbon dioxide. The two phases are linked by the energy carriers adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADP+).

Question: What is the most important role of chloroplasts?


Answer: photosynthesis

Question: What is the process of changing light into chemical energy?


Answer: food in the form of sugars

Question: What is chemical energy used to produce in plants?


Answer: Water (H2O) and carbon dioxide (CO2)

Question: What are the molecular inputs for photosynthesis?


Answer: sugar and oxygen (O2)

Question: What are the molecular outputs for photosynthesis?


Answer: generate ATP energy

Context: Like mitochondria, chloroplasts use the potential energy stored in an H+, or hydrogen ion gradient to generate ATP energy. The two photosystems capture light energy to energize electrons taken from water, and release them down an electron transport chain. The molecules between the photosystems harness the electrons' energy to pump hydrogen ions into the thylakoid space, creating a concentration gradient, with more hydrogen ions (up to a thousand times as many) inside the thylakoid system than in the stroma. The hydrogen ions in the thylakoid space then diffuse back down their concentration gradient, flowing back out into the stroma through ATP synthase. ATP synthase uses the energy from the flowing hydrogen ions to phosphorylate adenosine diphosphate into adenosine triphosphate, or ATP. Because chloroplast ATP synthase projects out into the stroma, the ATP is synthesized there, in position to be used in the dark reactions.

Question: What do chloroplasts do like mitochondria?


Answer: into the thylakoid space

Question: Where do chloroplasts pump hydrogen?


Answer: up to a thousand times

Question: How concentrated do the hydrogen ions get in the thylakoid space?


Answer: phosphorylate adenosine diphosphate

Question: What does ATP synthase change into ATP?


Answer: adenosine triphosphate

Question: What does ATP mean?


Answer: NADP+

Context: While photosystem II photolyzes water to obtain and energize new electrons, photosystem I simply reenergizes depleted electrons at the end of an electron transport chain. Normally, the reenergized electrons are taken by NADP+, though sometimes they can flow back down more H+-pumping electron transport chains to transport more hydrogen ions into the thylakoid space to generate more ATP. This is termed cyclic photophosphorylation because the electrons are recycled. Cyclic photophosphorylation is common in C4 plants, which need more ATP than NADPH.

Question: What usually takes reenergized electrons?


Answer: cyclic photophosphorylation

Question: In what process are electrons recycled?


Answer: in C4 plants

Question: Where is cyclic photophosphorylation common?


Answer: more ATP than NADPH

Question: What do C4 plants need?


Answer: The Calvin cycle

Context: The Calvin cycle starts by using the enzyme Rubisco to fix CO2 into five-carbon Ribulose bisphosphate (RuBP) molecules. The result is unstable six-carbon molecules that immediately break down into three-carbon molecules called 3-phosphoglyceric acid, or 3-PGA. The ATP and NADPH made in the light reactions is used to convert the 3-PGA into glyceraldehyde-3-phosphate, or G3P sugar molecules. Most of the G3P molecules are recycled back into RuBP using energy from more ATP, but one out of every six produced leaves the cycle—the end product of the dark reactions.

Question: What cycle starts with rubisco?


Answer: unstable six-carbon molecules that immediately break down

Question: What is the result of the Calvin cycle?


Answer: three-carbon molecules called 3-phosphoglyceric acid

Question: What do unstable 6-carbon molecules become?


Answer: one out of every six

Question: How many G3P molecules leave the cycle?


Answer: glucose monomers in the chloroplast can be linked together

Context: Alternatively, glucose monomers in the chloroplast can be linked together to make starch, which accumulates into the starch grains found in the chloroplast. Under conditions such as high atmospheric CO2 concentrations, these starch grains may grow very large, distorting the grana and thylakoids. The starch granules displace the thylakoids, but leave them intact. Waterlogged roots can also cause starch buildup in the chloroplasts, possibly due to less sucrose being exported out of the chloroplast (or more accurately, the plant cell). This depletes a plant's free phosphate supply, which indirectly stimulates chloroplast starch synthesis. While linked to low photosynthesis rates, the starch grains themselves may not necessarily interfere significantly with the efficiency of photosynthesis, and might simply be a side effect of another photosynthesis-depressing factor.

Question: What is an alternate way to make starch?


Answer: Under conditions such as high atmospheric CO2 concentrations

Question: When might starch grains become overly large?


Answer: distorting the grana and thylakoids

Question: What happens when starch grains become overly large?


Answer: Waterlogged roots

Question: What root problem can cause starch buildup?


Answer: another photosynthesis-depressing factor

Question: What might starch grains be a side effect of?


Answer: add O2 instead of CO2 to RuBP

Context: Photorespiration can occur when the oxygen concentration is too high. Rubisco cannot distinguish between oxygen and carbon dioxide very well, so it can accidentally add O2 instead of CO2 to RuBP. This process reduces the efficiency of photosynthesis—it consumes ATP and oxygen, releases CO2, and produces no sugar. It can waste up to half the carbon fixed by the Calvin cycle. Several mechanisms have evolved in different lineages that raise the carbon dioxide concentration relative to oxygen within the chloroplast, increasing the efficiency of photosynthesis. These mechanisms are called carbon dioxide concentrating mechanisms, or CCMs. These include Crassulacean acid metabolism, C4 carbon fixation, and pyrenoids. Chloroplasts in C4 plants are notable as they exhibit a distinct chloroplast dimorphism.

Question: What can rubisco do by mistake?


Answer: when the oxygen concentration is too high

Question: When does photorespiration happen?


Answer: it consumes ATP and oxygen, releases CO2, and produces no sugar

Question: Why is using O2 instead of CO2 less efficient?


Answer: up to half the carbon fixed by the Calvin cycle

Question: How much carbon gets wasted by using O2 instead of CO2?


Answer: they exhibit a distinct chloroplast dimorphism

Question: What is unusual about C4 plants' chloroplasts?


Answer: in their stroma

Context: Chloroplasts alone make almost all of a plant cell's amino acids in their stroma except the sulfur-containing ones like cysteine and methionine. Cysteine is made in the chloroplast (the proplastid too) but it is also synthesized in the cytosol and mitochondria, probably because it has trouble crossing membranes to get to where it is needed. The chloroplast is known to make the precursors to methionine but it is unclear whether the organelle carries out the last leg of the pathway or if it happens in the cytosol.

Question: Where do chloroplasts make amino acids?


Answer: cysteine and methionine

Question: Which amino acids contain sulfur?


Answer: it has trouble crossing membranes to get to where it is needed

Question: What is the problem with cysteine?


Answer: whether the organelle carries out the last leg of the pathway or if it happens in the cytosol

Question: What are we unsure of about how chloroplasts make methionine precursors?


Answer: Chloroplasts

Context: Chloroplasts are a special type of a plant cell organelle called a plastid, though the two terms are sometimes used interchangeably. There are many other types of plastids, which carry out various functions. All chloroplasts in a plant are descended from undifferentiated proplastids found in the zygote, or fertilized egg. Proplastids are commonly found in an adult plant's apical meristems. Chloroplasts do not normally develop from proplastids in root tip meristems—instead, the formation of starch-storing amyloplasts is more common.

Question: What is sometimes used interchangeably with 'plastids'?


Answer: undifferentiated proplastids found in the zygote, or fertilized egg

Question: What do a plant's chloroplasts descend from?


Answer: in an adult plant's apical meristems

Question: Where are Proplastids usually found?


Answer: the formation of starch-storing amyloplasts

Question: What is more often seen in root tip maristems?


Answer: proplastids may develop into an etioplast stage before becoming chloroplasts

Context: If angiosperm shoots are not exposed to the required light for chloroplast formation, proplastids may develop into an etioplast stage before becoming chloroplasts. An etioplast is a plastid that lacks chlorophyll, and has inner membrane invaginations that form a lattice of tubes in their stroma, called a prolamellar body. While etioplasts lack chlorophyll, they have a yellow chlorophyll precursor stocked. Within a few minutes of light exposure, the prolamellar body begins to reorganize into stacks of thylakoids, and chlorophyll starts to be produced. This process, where the etioplast becomes a chloroplast, takes several hours. Gymnosperms do not require light to form chloroplasts.

Question: What happens if angiosperm shoots don't get enough light?


Answer: a plastid that lacks chlorophyll

Question: What is an etioplast?


Answer: invaginations that form a lattice of tubes in their stroma

Question: What do etioplasts' internal membranes have?


Answer: a yellow chlorophyll precursor

Question: What do etioplasts have instead of chlorophyll?


Answer: Gymnosperms

Question: What plants don't need light to make chloroplasts?


Answer: chromoplasts

Context: Plastid differentiation is not permanent, in fact many interconversions are possible. Chloroplasts may be converted to chromoplasts, which are pigment-filled plastids responsible for the bright colors seen in flowers and ripe fruit. Starch storing amyloplasts can also be converted to chromoplasts, and it is possible for proplastids to develop straight into chromoplasts. Chromoplasts and amyloplasts can also become chloroplasts, like what happens when a carrot or a potato is illuminated. If a plant is injured, or something else causes a plant cell to revert to a meristematic state, chloroplasts and other plastids can turn back into proplastids. Chloroplast, amyloplast, chromoplast, proplast, etc., are not absolute states—intermediate forms are common.

Question: What can chloroplasts change into?


Answer: pigment-filled plastids responsible for the bright colors seen in flowers and ripe fruit

Question: What are chromoplasts?


Answer: chromoplasts

Question: What can amyloplasts become?


Answer: chromoplasts

Question: What can proplastids become?


Answer: chloroplasts and other plastids

Question: When a plant is injured, what can become proplastids?


Answer: filaments

Context: The division process starts when the proteins FtsZ1 and FtsZ2 assemble into filaments, and with the help of a protein ARC6, form a structure called a Z-ring within the chloroplast's stroma. The Min system manages the placement of the Z-ring, ensuring that the chloroplast is cleaved more or less evenly. The protein MinD prevents FtsZ from linking up and forming filaments. Another protein ARC3 may also be involved, but it is not very well understood. These proteins are active at the poles of the chloroplast, preventing Z-ring formation there, but near the center of the chloroplast, MinE inhibits them, allowing the Z-ring to form.

Question: What do FtsZ1 and FtsZ2 combine into?


Answer: proteins

Question: What are FtsZ1 and FtsZ2?


Answer: a structure called a Z-ring

Question: What do FtsZ1 and FtsZ2 plus ARC6 form?


Answer: within the chloroplast's stroma

Question: Where is the Z-ring?


Answer: The Min system

Question: What gets the Z-ring in the right place?


Answer: plastid-dividing rings

Context: Next, the two plastid-dividing rings, or PD rings form. The inner plastid-dividing ring is located in the inner side of the chloroplast's inner membrane, and is formed first. The outer plastid-dividing ring is found wrapped around the outer chloroplast membrane. It consists of filaments about 5 nanometers across, arranged in rows 6.4 nanometers apart, and shrinks to squeeze the chloroplast. This is when chloroplast constriction begins. In a few species like Cyanidioschyzon merolæ, chloroplasts have a third plastid-dividing ring located in the chloroplast's intermembrane space.

Question: What are PD rings?


Answer: two

Question: How many PD rings are there?


Answer: about 5 nanometers across

Question: How large are the outer PD ring's filaments?


Answer: 6.4 nanometers

Question: How far apart are the outer PD ring's filaments?


Answer: chloroplasts have a third plastid-dividing ring

Question: What is different about Cyanidioschyzon merolæ?


Answer: Light

Context: Light has been shown to be a requirement for chloroplast division. Chloroplasts can grow and progress through some of the constriction stages under poor quality green light, but are slow to complete division—they require exposure to bright white light to complete division. Spinach leaves grown under green light have been observed to contain many large dumbbell-shaped chloroplasts. Exposure to white light can stimulate these chloroplasts to divide and reduce the population of dumbbell-shaped chloroplasts.

Question: What is necessary for chloroplasts to replicate?


Answer: bright white light

Question: What kind of light is important for chloroplasts to divide?


Answer: large dumbbell-shaped

Question: What do chloroplasts look like in spinach grown in green light?


Answer: poor quality green light

Question: What kind of light is inadequate for chloroplasts to divide?


Answer: transgenes in these plastids cannot be disseminated by pollen

Context: Recently, chloroplasts have caught attention by developers of genetically modified crops. Since, in most flowering plants, chloroplasts are not inherited from the male parent, transgenes in these plastids cannot be disseminated by pollen. This makes plastid transformation a valuable tool for the creation and cultivation of genetically modified plants that are biologically contained, thus posing significantly lower environmental risks. This biological containment strategy is therefore suitable for establishing the coexistence of conventional and organic agriculture. While the reliability of this mechanism has not yet been studied for all relevant crop species, recent results in tobacco plants are promising, showing a failed containment rate of transplastomic plants at 3 in 1,000,000.

Question: Why are chloroplasts of interest in GMO crops?


Answer: environmental risks

Question: What is reduced by using plastid transformation for gene modification?


Answer: 3 in 1,000,000

Question: What was the containment failure rate in a tobacco plant study using plastid transformation?


Answer: transplastomic

Question: What are plants with plastid gene transformations called?


Answer: itself

Context: A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example, 5 is prime because 1 and 5 are its only positive integer factors, whereas 6 is composite because it has the divisors 2 and 3 in addition to 1 and 6. The fundamental theorem of arithmetic establishes the central role of primes in number theory: any integer greater than 1 can be expressed as a product of primes that is unique up to ordering. The uniqueness in this theorem requires excluding 1 as a prime because one can include arbitrarily many instances of 1 in any factorization, e.g., 3, 1 · 3, 1 · 1 · 3, etc. are all valid factorizations of 3.

Question: What is the only divisor besides 1 that a prime number can have?


Answer: composite number

Question: What are numbers greater than 1 that can be divided by 3 or more numbers called?


Answer: The fundamental theorem of arithmetic

Question: What theorem defines the main role of primes in number theory?


Answer: a product of primes

Question: Any number larger than 1 can be represented as a product of what?


Answer: because one can include arbitrarily many instances of 1 in any factorization

Question: Why must one be excluded in order to preserve the uniqueness of the fundamental theorem?


Answer: primality

Context: The property of being prime (or not) is called primality. A simple but slow method of verifying the primality of a given number n is known as trial division. It consists of testing whether n is a multiple of any integer between 2 and . Algorithms much more efficient than trial division have been devised to test the primality of large numbers. These include the Miller–Rabin primality test, which is fast but has a small probability of error, and the AKS primality test, which always produces the correct answer in polynomial time but is too slow to be practical. Particularly fast methods are available for numbers of special forms, such as Mersenne numbers. As of January 2016[update], the largest known prime number has 22,338,618 decimal digits.

Question: What is the name of the property that designates a number as being prime or not?


Answer: trial division

Question: What is the name of the process which confirms the primality of a number n?


Answer: the Miller–Rabin primality test

Question: What is the name of one algorithm useful for conveniently testing the primality of large numbers?


Answer: the AKS primality test

Question: What is the name of another algorithm useful for conveniently testing the primality of large numbers?


Answer: 22,338,618 decimal digits

Question: As of January 2016 how many digits does the largest known prime consist of?


Answer: infinitely many

Context: There are infinitely many primes, as demonstrated by Euclid around 300 BC. There is no known simple formula that separates prime numbers from composite numbers. However, the distribution of primes, that is to say, the statistical behaviour of primes in the large, can be modelled. The first result in that direction is the prime number theorem, proven at the end of the 19th century, which says that the probability that a given, randomly chosen number n is prime is inversely proportional to its number of digits, or to the logarithm of n.

Question: How many prime numbers exist?


Answer: Euclid

Question: Who established the amount of prime numbers in existence?


Answer: the statistical behaviour

Question: What type of behavior in primes is it possible to determine?


Answer: the prime number theorem

Question: What theorem states that the probability that a number n is prime is inversely proportional to its logarithm?


Answer: at the end of the 19th century

Question: When was the prime number theorem proven?


Answer: Goldbach's conjecture

Context: Many questions regarding prime numbers remain open, such as Goldbach's conjecture (that every even integer greater than 2 can be expressed as the sum of two primes), and the twin prime conjecture (that there are infinitely many pairs of primes whose difference is 2). Such questions spurred the development of various branches of number theory, focusing on analytic or algebraic aspects of numbers. Primes are used in several routines in information technology, such as public-key cryptography, which makes use of properties such as the difficulty of factoring large numbers into their prime factors. Prime numbers give rise to various generalizations in other mathematical domains, mainly algebra, such as prime elements and prime ideals.

Question: What is the name of the supposition that any number larger than 2 can be represented as the sum of two primes?


Answer: the twin prime conjecture

Question: What is the name of the supposition that there are infinite pairs of primes whose difference is 2?


Answer: algebraic aspects

Question: Besides the analytic property of numbers, what other property of numbers does number theory focus on?


Answer: public-key cryptography

Question: What is the application of prime numbers used in information technology which utilizes the fact that factoring very large prime numbers is very challenging?


Answer: prime ideals

Question: What is the name of one algebraic generalization prime numbers have inspired?


Answer: 2

Context: Hence, 6 is not prime. The image at the right illustrates that 12 is not prime: 12 = 3 · 4. No even number greater than 2 is prime because by definition, any such number n has at least three distinct divisors, namely 1, 2, and n. This implies that n is not prime. Accordingly, the term odd prime refers to any prime number greater than 2. Similarly, when written in the usual decimal system, all prime numbers larger than 5 end in 1, 3, 7, or 9, since even numbers are multiples of 2 and numbers ending in 0 or 5 are multiples of 5.

Question: Any even number larger than what cannot be considered prime?


Answer: 1, 2, and n

Question: What are the specific divisors of all even numbers larger than 2?


Answer: odd prime

Question: What name is given to any prime number larger than 2?


Answer: 9

Question: Besides 1,3 and 7, what other number must all primes greater than 5 end with?


Answer: even numbers

Question: What type of numbers are always multiples of 2?


Answer: 1

Context: Most early Greeks did not even consider 1 to be a number, so they could not consider it to be a prime. By the Middle Ages and Renaissance many mathematicians included 1 as the first prime number. In the mid-18th century Christian Goldbach listed 1 as the first prime in his famous correspondence with Leonhard Euler -- who did not agree. In the 19th century many mathematicians still considered the number 1 to be a prime. For example, Derrick Norman Lehmer's list of primes up to 10,006,721, reprinted as late as 1956, started with 1 as its first prime. Henri Lebesgue is said to be the last professional mathematician to call 1 prime. By the early 20th century, mathematicians began to accept that 1 is not a prime number, but rather forms its own special category as a "unit".

Question: What number did early Greeks not regard as a true number?


Answer: Christian Goldbach

Question: Who included 1 as the first prime number in the mid 18th century?


Answer: Leonhard Euler

Question: In the mid 18th century, who did not concur that 1 should be the first prime number?


Answer: 10,006,721

Question: How many primes were included in Derrick Norman Lehmer's list of prime numbers?


Answer: its own special category as a "unit"

Question: What type of number do modern mathematicians consider 1 to be?


Answer: Euclid's fundamental theorem of arithmetic

Context: A large body of mathematical work would still be valid when calling 1 a prime, but Euclid's fundamental theorem of arithmetic (mentioned above) would not hold as stated. For example, the number 15 can be factored as 3 · 5 and 1 · 3 · 5; if 1 were admitted as a prime, these two presentations would be considered different factorizations of 15 into prime numbers, so the statement of that theorem would have to be modified. Similarly, the sieve of Eratosthenes would not work correctly if 1 were considered a prime: a modified version of the sieve that considers 1 as prime would eliminate all multiples of 1 (that is, all other numbers) and produce as output only the single number 1. Furthermore, the prime numbers have several properties that the number 1 lacks, such as the relationship of the number to its corresponding value of Euler's totient function or the sum of divisors function.

Question: Which theorem would be invalid if the number 1 were considered prime?


Answer: if 1 were considered a prime

Question: The sieve of Eratosthenes would not be valid if what were true?


Answer: Euler's totient function

Question: What is another function that primes have that the number 1 does not?


Answer: the sum of divisors function

Question: What is one function that prime numbers have that 1 does not?


Answer: only the single number 1

Question: If 1 were to be considered as prime what would the sieve of Eratosthenes yield for all other numbers?


Answer: the Rhind papyrus

Context: There are hints in the surviving records of the ancient Egyptians that they had some knowledge of prime numbers: the Egyptian fraction expansions in the Rhind papyrus, for instance, have quite different forms for primes and for composites. However, the earliest surviving records of the explicit study of prime numbers come from the Ancient Greeks. Euclid's Elements (circa 300 BC) contain important theorems about primes, including the infinitude of primes and the fundamental theorem of arithmetic. Euclid also showed how to construct a perfect number from a Mersenne prime. The Sieve of Eratosthenes, attributed to Eratosthenes, is a simple method to compute primes, although the large primes found today with computers are not generated this way.

Question: What is the name of the Egyptian papyrus that suggests that they may have had knowledge of prime numbers?


Answer: the Ancient Greeks

Question: What civilization was the first known to clearly study prime numbers?


Answer: Euclid's Elements

Question: What work from around 300 BC has significant theorems about prime numbers?


Answer: Euclid

Question: Who demonstrated how to create a perfect number from a Mersenne prime?


Answer: compute primes

Question: What does the Sieve of Eratosthenes do?


Answer: In 1640

Context: After the Greeks, little happened with the study of prime numbers until the 17th century. In 1640 Pierre de Fermat stated (without proof) Fermat's little theorem (later proved by Leibniz and Euler). Fermat also conjectured that all numbers of the form 22n + 1 are prime (they are called Fermat numbers) and he verified this up to n = 4 (or 216 + 1). However, the very next Fermat number 232 + 1 is composite (one of its prime factors is 641), as Euler discovered later, and in fact no further Fermat numbers are known to be prime. The French monk Marin Mersenne looked at primes of the form 2p − 1, with p a prime. They are called Mersenne primes in his honor.

Question: In what year did Pierre de Fermat declare Fermat's little theorem?


Answer: Euler

Question: Besides Leibniz, what other mathematician proved the validity of Fermat's little theorem?


Answer: 22n + 1

Question: Of what form do Fermat numbers take?


Answer: 2p − 1

Question: Of what form do Mersenne primes take?


Answer: up to n = 4 (or 216 + 1)

Question: To what extent did Fermat confirm the validity of Fermat numbers?


Answer: trial division

Context: The most basic method of checking the primality of a given integer n is called trial division. This routine consists of dividing n by each integer m that is greater than 1 and less than or equal to the square root of n. If the result of any of these divisions is an integer, then n is not a prime, otherwise it is a prime. Indeed, if is composite (with a and b ≠ 1) then one of the factors a or b is necessarily at most . For example, for , the trial divisions are by m = 2, 3, 4, 5, and 6. None of these numbers divides 37, so 37 is prime. This routine can be implemented more efficiently if a complete list of primes up to is known—then trial divisions need to be checked only for those m that are prime. For example, to check the primality of 37, only three divisions are necessary (m = 2, 3, and 5), given that 4 and 6 are composite.

Question: What is the most elemental way to test the primality of any integer n?


Answer: if a complete list of primes up to is known

Question: What makes the method of trial division more efficient?


Answer: greater than 1

Question: Trial division involves dividing n by every integer m greater than what?


Answer: only three divisions

Question: How many divisions are required to verify the primality of the number 37?


Answer: less than or equal to the square root of n

Question: What must the integer m be less than or equal to when performing trial division?