How would the following changes affect enzyme activity for an ...

Question

How would the following changes affect enzyme activity for an enzyme whose optimal conditions are normal body temperature and physiological pH?

a. raising the temperature from 37 °C to 60 °C

Accepted Answer

Alright, hello everyone. So this question says if the temperature is raised from 37 °C to 70 °C, how would this change affect the activity of an enzyme that functions optimally at normal body temperature and physiological? Ph. So here we have four different statements labeled one through four, which we'll discuss later on in this video and we have four different answer options labeled A through D proposing which of the four statements are correct. So first, the first point that I want to reiterate is that the vast majority of enzymes are proteins. And the reason I say that is because the structure of a protein, in other words, the structure of an enzyme in this case, is going to heavily impact the function of that protein of that enzyme. So changes in the structure of the protein factors that change the structure will affect its function more than likely it's going to affect the function in a negative way. Now, factors that can affect the structure of an enzyme include things like temperature and also ph. So because enzymes are so sensitive to changes in factors like temperature and ph we often describe a set of optimal conditions for a given enzyme. So optimal conditions are conditions where the enzyme is at its most active at its most effective. Now, when you stray too far from the optimal range, right, this is where you begin to see changes in the structure which therefore reduce the function of the enzyme. So going back to the statement given right, this theoretical enzyme is going to function optimally at body temperature which is around 37 °C. So 37 °C is the enzyme's preferred temperature. But oftentimes there is some flexibility. In other words, the temperature can range or can vary a little bit but not too much. Because as soon as we straight passed the optimal temperature of the enzyme, let's say, for example, 50 degrees at this point, the intermolecular forces holding the protein, holding the enzyme together, maintaining a three dimensional shape are going to be disrupted. And so by this point, by the time we get to around 50 °C, in most cases, enzymes begin to denature. Now, the denaturing of a protein can be described as the unfolding of that protein because once again, these intermolecular forces holding the protein together will be disrupted at this high temperature. So then as you increase the temperature some more, let's say we get to 70 °C. Now, at this point, the enzyme is likely to be completely unfolded, likely to be completely denatured. And so once the enzyme has lost its structure, it has lost its function. And so it's not really going to be active by the time we get to a temperature as high as 70 °C. So with all this context in mind, let's start with statement number one, which reads that the enzymes activity will decrease as the temperature rises from 37 °C to 70 °C, improving the rate of the reaction. Now it's the last bit that makes the statement untrue, right? Because if the enzymes activity is decreasing, the rate of the reaction should also decrease. So statement one is not true. Statement two says that the enzyme's activity will decrease because the high temperature will likely denature the enzyme reducing its effectiveness. This is true, right? Because as mentioned before, by the time we get to a temperature as high as 70 °C, the protein, the enzyme I should say is more than likely to be completely denatured. So if it lost its structure, the enzyme has lost its function leading to decreased activity or decreased effectiveness. Moving on now to sacred three, it says that the enzyme may become completely inactive at 70 °C due to irreversible denaturation. This is true right. By the time we get to a temperature as high as 70 °C denaturation is more than likely, which means that the enzyme will no longer be able to perform its function. So three is also correct. Now, statement four says that the enzymes activity will initially increase as the temperature rises, but then decrease sharply as it approaches 70 °C due to denaturation. Now, state four is actually true as well because there's a little bit of nuance that I didn't mention earlier. So going back to this little line here that I drew with temperatures, let's start off at 37 °C at a certain point, right, enzyme activity increases with temperature just a little bit. And the reason for this is because as you increase the temperature, what you're doing is giving the enzymes and the substrate slightly more energy. And so when the enzyme and substrate have a higher energy, there are more frequent collisions between them. And so if they collide more, then the reaction is more likely to occur, which would increase the reaction rate. Now again, this is only up to a certain point. So it's very important to recognize that the range of temperatures in which an enzyme generally functions is very narrow or at least relatively narrow. So statement four is true, right? Because as you operate within that narrow range, enzyme activity does increase as the temperature rises. But once you pass that optimal range activity of the enzyme decreases sharply because by that point, it's going to begin to unfold. All right. So with all this said, right, of the four statements provided 23 and four are correct, which means that option C is going to be our answer here. And so if you watch this video all the way through, thank you so very much for doing so. And I hope you found this helpful.

How would the following changes affect enzyme activity for an enzyme whose optimal conditions are normal body temperature and physiological pH?
a. raising the temperature from 37 °C to 60 °C

Key Concepts

Enzyme Activity

Temperature Effects on Enzymes

Denaturation

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