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But how does that glucose actually make its way into the cells of our body? | Introduction to Glucose Metabolism .txt |
Or more generally, how does the glucose actually make its way into our body in the first place? | Introduction to Glucose Metabolism .txt |
Well, via the ingestion of food. | Introduction to Glucose Metabolism .txt |
So if we eat a meal that is rich in carbohydrates, that's how the glucose actually makes its way into our body. | Introduction to Glucose Metabolism .txt |
So there are two types of sugar molecules carbohydrates that we typically ingest. | Introduction to Glucose Metabolism .txt |
So carbohydrates polysaccharides that come from plants, and carbohydrates polysaccharides that come from animals. | Introduction to Glucose Metabolism .txt |
Now, for instance, if we eat a piece of chicken, that chicken not only has protein and fat, it also contains polysaccharides carbohydrates store in a form we call glycogen, which is the same form that we mentioned just a moment ago. | Introduction to Glucose Metabolism .txt |
Now, if we ingest things like pasta or bread or cereal, these are actually polysaccharides that come from plants. | Introduction to Glucose Metabolism .txt |
And so what we're ingesting is starch. | Introduction to Glucose Metabolism .txt |
And there are two types of starch. | Introduction to Glucose Metabolism .txt |
So we have amylose and amylopectin. | Introduction to Glucose Metabolism .txt |
So one of them is basically a linear helical structure that's the amylose. | Introduction to Glucose Metabolism .txt |
And the amylopectin is like the glycogen, actually a branched form of starch. | Introduction to Glucose Metabolism .txt |
Now, we see that these polysaccharides are inherently too large to actually fit into our cells, and they're too large to actually move around and transport in the blood plasma. | Introduction to Glucose Metabolism .txt |
And so before these large polysaccharides actually make their way into the blood plasma of our body and into our cells, these carbohydrates must be broken down into smaller components. | Introduction to Glucose Metabolism .txt |
In fact, they must be broken down into these individual glucose molecules before the cells can actually uptake those glucose molecules and store the glucose as glycogen, or break down the glucose to form ATP molecules. | Introduction to Glucose Metabolism .txt |
So the question is, what are these enzymes, digestive enzymes, proteases, that basically break down these carbohydrates into their individual monomeric form? | Introduction to Glucose Metabolism .txt |
Well, we have many different types of enzymes, and I've listed six enzymes, actually seven enzymes on the board. | Introduction to Glucose Metabolism .txt |
And let's begin with a salivary alpha amylase. | Introduction to Glucose Metabolism .txt |
So salivary simply means it exists in a saliva. | Introduction to Glucose Metabolism .txt |
So when we eat food and where we're chewing the food, that saliva actually contains a specific type of digestive enzyme and proteins known as alpha amylase. | Introduction to Glucose Metabolism .txt |
And what the alpha amylase does is it begins to cleave alpha one four glycocity linkages that exist in the starch as well as glycogen. | Introduction to Glucose Metabolism .txt |
So this begins the cleavage of alpha one four glycocity linkages in the mouth, and this breaks it down to smaller polysaccharides and oligosaccharides. | Introduction to Glucose Metabolism .txt |
Now, from the mouth, it moves via the esophagus, eventually makes its way into our stomach. | Introduction to Glucose Metabolism .txt |
Now, in the stomach, nothing actually breaks down. | Introduction to Glucose Metabolism .txt |
So what that means is the actual glycocitic linkages, the bonds don't break down in the stomach, but once it makes its way into the small intestine, that's when the rest of that digestion actually takes place, because the pancreas produces a specific type of carbohydrate digestive enzyme known as pancreatic alpha amylase. | Introduction to Glucose Metabolism .txt |
And this is much more potent and much more powerful than the salivary alpha amylase. | Introduction to Glucose Metabolism .txt |
So the pancreatic alpha amylase also is able to break down those same alpha one four glycocytic linkages, but this actually breaks down the polysaccharide into either disaccharides or trisaccharides. | Introduction to Glucose Metabolism .txt |
So in the case of starch or glycogen, we basically break down these individual polysaccharides into maltose molecules, which are disaccharides. | Introduction to Glucose Metabolism .txt |
That consists of two glucose or trisaccharides, that consists of three glucose known as maltotrios. | Introduction to Glucose Metabolism .txt |
Now, the actual cells on the epithelium of the small intestine actually contain these secretory vesicles, these granules that themselves contain enzymes. | Introduction to Glucose Metabolism .txt |
And so these are the enzymes that they basically have. | Introduction to Glucose Metabolism .txt |
So we have Maltase, we have alpha glucosedase, we have alpha dextrinase, we have sucrase and lactase. | Introduction to Glucose Metabolism .txt |
And all of these enzymes are basically specific to the type of molecules and type of bonds they actually cleave. | Introduction to Glucose Metabolism .txt |
So, for instance, in the case of Maltase, maltase is released by the cells on the brush border, and this enzyme basically breaks down the Maltose. | Introduction to Glucose Metabolism .txt |
So here we said the pancreatic alpha amylase breaks down the ligosaccharides and polysaccharides that could not be broken down by the salivary alpha amylase into Maltose or Maltotria. | Introduction to Glucose Metabolism .txt |
And these Maltose molecules are broken down by these maltase enzymes at the brush border of our epithelium of the small intestine. | Introduction to Glucose Metabolism .txt |
And once the Maltose is broken down into the glucose constituents, then the glucose can actually be taken by the cell by using a special type of glucose transporter, as we'll discuss in a future lecture. | Introduction to Glucose Metabolism .txt |
Now, we also mentioned the meltotrios, and we have another type of enzyme, a different enzyme known as alpha glucose, a dase, that basically breaks down the meltotrials into the three constituent glucose molecules. | Introduction to Glucose Metabolism .txt |
And only then can the glucose molecules can actually make their way into the cell of our body. | Introduction to Glucose Metabolism .txt |
Then we also have alpha dextronose or dextrinase. | Introduction to Glucose Metabolism .txt |
Now, in the case of alpha dextronate, so let's go back to starch and glycogen. | Introduction to Glucose Metabolism .txt |
So if we discuss so if we ingest the amylopectin version of starch or glycogen, we know that these two types of polysaccharides not only have the alpha one four glycocity bonds, they also have the alpha one six glycocytic bonds. | Introduction to Glucose Metabolism .txt |
And the alpha amylase found in our mouth and the alpha amylase found in our small intestine that is produced by the pancreas, these cannot break down those alpha one six linkages. | Introduction to Glucose Metabolism .txt |
And that's where this alpha dextronase actually comes into play. | Introduction to Glucose Metabolism .txt |
So the alpha dextronase basically breaks down the limited xray, which is basically those oligosaccharides that contain the alpha one six bonds which were not broken down by either of these two types of enzymes. | Introduction to Glucose Metabolism .txt |
And so it's this one that breaks down these dextrin molecules, breaks down those alpha one six linkages, breaks the molecules into their individual constituent glucose molecules, and then the glucose is ingested into our cell. | Introduction to Glucose Metabolism .txt |
Now, glucose molecules are not the only sugar molecules that we actually ingest into our body. | Introduction to Glucose Metabolism .txt |
We can also ingest, for instance, galactase we can ingest or galactose we can ingest fructose and so forth. | Introduction to Glucose Metabolism .txt |
And so we have many other examples of enzymes that are used to break down these specific types of glycosytic bonds. | Introduction to Glucose Metabolism .txt |
So we have Succeed, which basically breaks down the glycocitic bond between fructose and sugar and fructose and glucose. | Introduction to Glucose Metabolism .txt |
So when fructose and glucose combined, they form sucrose, and sucrase breaks down sucrose. | Introduction to Glucose Metabolism .txt |
So sucrose is essentially a mobile form of a carbohydrate sugar molecule found inside plants. | Introduction to Glucose Metabolism .txt |
So when we eat plants, we can also actually eat these sucrose molecules. | Introduction to Glucose Metabolism .txt |
And so Succeed is responsible for breaking down sucrose. | Introduction to Glucose Metabolism .txt |
Now, we also have lactase. | Introduction to Glucose Metabolism .txt |
So lactase is essentially a digestive enzyme that breaks down lactose. | Introduction to Glucose Metabolism .txt |
And lactose is a disaccharide that consists of glucose and galactose. | Introduction to Glucose Metabolism .txt |
And lactose we obtain from dairy products, from milk. | Introduction to Glucose Metabolism .txt |
So if we drink milk inside milk, we'll find these lactose disaccharides. | Introduction to Glucose Metabolism .txt |
And it's the lactose that breaks down these disaccharides into their individual monomers. | Introduction to Glucose Metabolism .txt |
So once all these different types of enzymes and many more, they basically break down all the different types of carbohydrates inside the small intestine. | Introduction to Glucose Metabolism .txt |
Only then can these actually make their way into the cytoplasm of our cells and into the blood via this process of transport. | Introduction to Glucose Metabolism .txt |
By using these special types of membrane transport protein molecules. | Introduction to Glucose Metabolism .txt |
In biochemistry, it's very useful to be able to determine what the sequence of nucleotides in some DNA molecule. | Sanger Sequencing of DNA .txt |
Because if we know what the sequence of nucleotides is, that will give us information about how gene expression takes place and what types of proteins are produced. | Sanger Sequencing of DNA .txt |
Now, what's the process by which we can actually sequence our DNA molecule? | Sanger Sequencing of DNA .txt |
Well, the process is known as Sanger dioxine method, or simply Sanger DNA sequencing. | Sanger Sequencing of DNA .txt |
Now, before we discuss the steps of this process, let's discuss an important molecule used in this process and let's see why it is actually used. | Sanger Sequencing of DNA .txt |
So the molecule is this molecule here. | Sanger Sequencing of DNA .txt |
It's called two prime, three prime dioxy nucleuside triphosphate or simply Ddntp. | Sanger Sequencing of DNA .txt |
Now, this molecule is almost identical to a normal deoxy nucleuside triphosphate. | Sanger Sequencing of DNA .txt |
The only difference is the sugar component contains a three prime carbon that does not contain a hydroxyl group. | Sanger Sequencing of DNA .txt |
So remember, in a normal deoxy nucleus triphosphate, the presence of the hydroxyl group on the three prime carbon allows DNA polymerase to actually form a phosphodiastor bond with the next nucleotide in line. | Sanger Sequencing of DNA .txt |
So in the process of DNA synthesis, when we're replicating a DNA strand, the DNA polymerase needs this hydroxyl group to be present on the three prime carbon to actually form the phosphodiaester bond. | Sanger Sequencing of DNA .txt |
And if that hydroxyl group is not present, as in this case, it will not be able to form that phospholdiaester bond. | Sanger Sequencing of DNA .txt |
And so DNA replication would essentially stop. | Sanger Sequencing of DNA .txt |
And so what this DD NTP molecule is used for in this method is to basically stop the process of DNA replication. | Sanger Sequencing of DNA .txt |
And we'll see why that's important towards the end of this lecture. | Sanger Sequencing of DNA .txt |
So let's move on to these four steps. | Sanger Sequencing of DNA .txt |
So, in step one of the standard DNA sequencing, we have to actually obtain that DNA molecule that we want to sequence. | Sanger Sequencing of DNA .txt |
So let's suppose we have a double stranded DNA molecule as shown on the board. | Sanger Sequencing of DNA .txt |
Now, the second step of this process will involve DNA replication. | Sanger Sequencing of DNA .txt |
And remember, DNA replication only takes place if the two strands of DNA have separated. | Sanger Sequencing of DNA .txt |
So, in step one, what we essentially want to do is we want to denature the double helix structure of the DNA. | Sanger Sequencing of DNA .txt |
We want to separate the two strands of DNA, and the way that we're going to separate them is by adding sodium hydroxide. | Sanger Sequencing of DNA .txt |
So remember, a base or an acid, if we mix the DNA in either a basic or acidic solution, in this case a basic, the base will essentially ionize the bases of our DNA molecule and that will disrupt and break the hydrogen bonds. | Sanger Sequencing of DNA .txt |
And so if we take the double strand DNA molecule and we add sodium hydroxide, we produce these two individual strands of DNA. | Sanger Sequencing of DNA .txt |
Now, one of these single strands of DNA can actually be chosen for the sequencing process. | Sanger Sequencing of DNA .txt |
Now, it doesn't matter which one of these DNA strands we choose, because if we choose this one, for example, then once we determine the sequence of this DNA strand, we can easily determine what the sequence of the other strand is because these two strands are complementary. | Sanger Sequencing of DNA .txt |
They have complementary base pairing. | Sanger Sequencing of DNA .txt |
So the G bases with our C and the A bases with our T. So once we know this sequence, we know what the other sequence is simply by the base parent process. | Sanger Sequencing of DNA .txt |
So let's choose this single stranded DNA molecule. | Sanger Sequencing of DNA .txt |
We isolate it, we place it into our beaker that contains only this molecule here. | Sanger Sequencing of DNA .txt |
And then we move on to step number two. | Sanger Sequencing of DNA .txt |
And in step number two, we want to basically replicate this DNA molecule. | Sanger Sequencing of DNA .txt |
And so what that means is we need three different things. | Sanger Sequencing of DNA .txt |
We need a DNA primer, we need DNA polymerase and we need the building blocks, the four types of normal deoxy nucleotide triphosphate. | Sanger Sequencing of DNA .txt |
So in step two, the solution containing the single strand of DNA, this one here is mixed with number one or a a labeled radioactively labeled DNA primer. | Sanger Sequencing of DNA .txt |
So we need the DNA primer basically for that DNA polymerase to actually work. | Sanger Sequencing of DNA .txt |