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And so to increase V the rate of that reaction, the enzyme must increase the value of K. Now what exactly is the order of the reaction? | Effect of Enzymes on Rate Law and Rate Constant .txt |
So earlier we said that the order of this reaction was one and the order of this reaction was also one. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And the same thing was true for this particular case. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So we see that the order of the reaction basically describes the rate of the reaction and how it actually depends on the concentration of those reactants. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So let's begin with the first order reaction that we basically described in this lecture. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So when a reaction rate is directly proportional to the concentration of the reactant, it is set to be first order with respect to that reactant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So in this particular case, because the exponent is one, this is a first order reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And that means the rate law or the rate of that particular reaction depends directly, is directly proportional to the concentration. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So by doubling the concentration of A, we double the rate by quadrupling it, we quadruple the rate, by tripling it, we triple the rate and so forth. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So if we have a direct correlation between the reactant concentration and the rate of the reaction, then that means that reactant is first order with respect to that particular reactant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now to calculate the overall order of that particular reaction we have to sum up all the exponents in that particular chemical rate law. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And so because in this particular case we only have one exponent, that means the rate, the order is first. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And in this particular case the order is also first. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But if we for example move on to a second order reaction, let's suppose we have A and B are the two reactants and they react to produce C. And this k value is basically the reaction constant, the rate constant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now if A is first order and B is also first order, then this will be our rate law. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So the rate of the reaction v is equal to k, that rate constant multiplied by the concentration of A to the power of one and the concentration of B to the power of one. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And the overall order of this reaction is one plus one. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So we simply sum up the exponents and that gives us two. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And what that means is by doubling A we double v as long as everything else remains constant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Likewise, if we double B while A and K is constant, v will also double. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But if we double A and B while K is constant, we quadruple that v value. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And so that's what it means for reaction to actually be 1st 2nd order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now we can also have a slightly different second order reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So in this case we have two reactants. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But what if we have a single reactant? | Effect of Enzymes on Rate Law and Rate Constant .txt |
So let's suppose we have A and A basically converts to form B. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And let's suppose that we have two moles of A, produces 1 mol of B and this is an elementary reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So this is the k value, the rate constant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And so in this case, the rate law v is equal to k multiplied by the concentration of A. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But because this is an elementary reaction and the coefficient is two, what that means is we'll have a coefficient of two on top of that A. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So this reaction is second order with respect to K and with respect to A. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And the overall order is also second order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So this reaction and this reaction, they are both second order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
The only difference is we have a single reactant here but we have two reactants here. | Effect of Enzymes on Rate Law and Rate Constant .txt |
In this particular case if we double A, then we quadruple the velocity because two to the power of two gives us four. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But in this case by doubling A we essentially double v if everything else is kept constant. | Effect of Enzymes on Rate Law and Rate Constant .txt |
But if we double A and B and we keep K constant then we quadruple the value of v and finally we can also have 0th order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And in the 0th order basically the concentration of the reactant has no effect on the rate of that reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
So if a reaction is 0th order with respect to some reactant then the rate is independent of that reactant's concentration. | Effect of Enzymes on Rate Law and Rate Constant .txt |
For instance, if we have A and A is transformed into B and K is the rate constant and we know that A is zero's order, what that basically means is the exponent will be zero. | Effect of Enzymes on Rate Law and Rate Constant .txt |
This will become one. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And so the rate law is v is equal to K. And notice that changing A, either increasing or decreasing will not affect the value of V. And some enzyme catalyze reactions inside our body are in fact 0th order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And what that means is by changing the concentration of A that will not affect that rate of the reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now we can also have something known as a pseudo first order reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
And a pseudo first order reaction is actually a second order reaction that behaves like it's a first order reaction. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now what's one example of such a reaction? | Effect of Enzymes on Rate Law and Rate Constant .txt |
Well, let's suppose is we have a second order reaction as shown, but the concentration of A is very tiny but the concentration of B is very, very high. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Now in this particular case even though it's a second order reaction it will behave like a first order. | Effect of Enzymes on Rate Law and Rate Constant .txt |
Proteins are an extremely diverse group of macromolecules, and that's partially because they consist of 20 different amino acids. | Modification of Amino Acids .txt |
So by arranging the amino acids in some specific sequence, we basically create a particular type of shape for that protein. | Modification of Amino Acids .txt |
And that shape dictates what the function of that protein is. | Modification of Amino Acids .txt |
And so by changing the arrangement of our amino acids, we we can basically create a different protein with a different type of function. | Modification of Amino Acids .txt |
Now, in addition to increase the functionality and the diversity of the functionality of our proteins, we can basically modify the proteins by modifying the amino acids. | Modification of Amino Acids .txt |
And there are five common ways by which our cells modify amino acids, as we'll see in just a moment. | Modification of Amino Acids .txt |
Actually, there are many more ways, but we're going to focus on these five in this lecture. | Modification of Amino Acids .txt |
So we can modify amino acids by adding acetal groups, hydroxyl groups, carboxyl groups, sugar groups, phosphoryl groups, as well as many other different types of groups which we're going to discuss in future lectures. | Modification of Amino Acids .txt |
So in this lecture, let's focus on these five. | Modification of Amino Acids .txt |
So let's begin with the first one. | Modification of Amino Acids .txt |
So the majority of the polypeptides and proteins inside our body are actually modified by the addition of acetyl groups. | Modification of Amino Acids .txt |
And that's because what this does is it tells our cells not to break down and degrade those polypeptide. | Modification of Amino Acids .txt |
So many proteins are acetylated at the terminal amino groups to prevent degradation by our cells. | Modification of Amino Acids .txt |
So if we go to the beginning of our polypeptide, the nitrogen is basically modified by adding this acetal group. | Modification of Amino Acids .txt |
And what that does is it prevents this polypeptide from being broken down. | Modification of Amino Acids .txt |
Now, another way by modifying proteins is by adding on hydroxyl groups. | Modification of Amino Acids .txt |
And one common example is Collagen. | Modification of Amino Acids .txt |
So Collagen is by far the most abundant protein found in our body. | Modification of Amino Acids .txt |
It is found mostly in the extracellular tissue in our connective tissue, such as, for example, bone. | Modification of Amino Acids .txt |
And what Collagen does is it gives our tissue its strength. | Modification of Amino Acids .txt |
So what is the structure of Collagen? | Modification of Amino Acids .txt |
Well, Collagen has a coronary structure, and one of the most abundant amino acids in Collagen is proline. | Modification of Amino Acids .txt |
Now, what Collagen does is it modifies the structure of proline by adding a hydroxyl group to produce hydroxyproline. | Modification of Amino Acids .txt |
And what that does is it increases the stability of the three dimensional structure of Collagen. | Modification of Amino Acids .txt |
So Collagen, the most abundant protein in our body, contains proline amino acids that contain hydroxyl groups. | Modification of Amino Acids .txt |
These hydroxyl groups, as shown in the following diagram, basically give the Collagen its stability. | Modification of Amino Acids .txt |
Now, what happens if we can't produce these hydroxyproline groups? | Modification of Amino Acids .txt |
Well, basically, a condition in humans of a disease known as Scurvy is essentially this inability of Collagen to basically produce and modify its own proline molecules in the following way. | Modification of Amino Acids .txt |
So, in Scurvy, the body has a deficiency of vitamin C, and vitamin C is needed to basically modify and convert the proline molecules into hydroxyproline. | Modification of Amino Acids .txt |
And so, because we can't modify these amino acids in this way, the structure of collagen basically is destabilized. | Modification of Amino Acids .txt |
And what that means is it decreases the strength of our tissue. | Modification of Amino Acids .txt |
Now let's move on to carboxyl groups. | Modification of Amino Acids .txt |
So once again, many different types of proteins inside the body can be modified by the addition of carboxyl groups. | Modification of Amino Acids .txt |
And one particular example is a protein and enzyme in the blood clotting cascade we call prothrombin. | Modification of Amino Acids .txt |
So prothrombin is needed to basically stop bleeding. | Modification of Amino Acids .txt |
And if prothrombin can't stop bleeding, then what that means is we're going to get a condition known as hemorrhage. | Modification of Amino Acids .txt |
Now, what happens is in some cases if, for example, our glutamate amino acid in prothrombin cannot be modified by this process of carboxylation, the addition of this carboxyl group, then our prothrombin will essentially not be as active, it will not be able to carry out its function correctly. | Modification of Amino Acids .txt |
And that can lead to the condition we call hemorrhage. | Modification of Amino Acids .txt |
Now, let's move on to addition of sugar group. | Modification of Amino Acids .txt |
So many, many proteins inside our body are modified by adding carbohydrate components. | Modification of Amino Acids .txt |
For example, the proteins that are destined to be in a cell membrane or outside the cell, they're modified in this way. | Modification of Amino Acids .txt |
And the reason we add carbohydrate components is to basically increase the polarity, increase the hydrophilic nature of those proteins, so that they can interact better with other proteins as well as with other hydrophilic molecules. | Modification of Amino Acids .txt |
So, for example, we can have asparagne, the amino acid asparagine be modified by the addition of the sugar component. | Modification of Amino Acids .txt |
And all these different hydroxyl groups basically increases the hydrophilic nature of that protein. | Modification of Amino Acids .txt |
Finally, we can also undergo the process of phosphorylation. | Modification of Amino Acids .txt |
We can add these phosphoryl groups onto our amino acids. | Modification of Amino Acids .txt |
In fact, many different types of cellular processes that take place inside our cells and inside our body use the phosphorylation as a way to turn on and off these different types of cell processes. | Modification of Amino Acids .txt |
For example, epinephrine, a hormone, and a newer transmitter can act on the serene and three anion amino acids by phosphorylating them. | Modification of Amino Acids .txt |
And that can turn on or off many different types of molecules and reactions of processes that exist inside our body. | Modification of Amino Acids .txt |
For example, insulin, which is a molecule that is used to regulate the amount of glucose found inside our body, inside our blood functions via this process. | Modification of Amino Acids .txt |
So we can turn on or off insulin by using these phosphoryl groups. | Modification of Amino Acids .txt |
Now, finally, we can also not only modify the amino acids, but in some cases when we cleave peptides within the proteins, within our polypeptide that can activate or deactivate our protein. | Modification of Amino Acids .txt |
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