V 0 for an enzyme-catalyzed reaction:

Alright. So this practice problem wants us to indicate which of these 6 potential answer options below best corresponds with the problem, which mentions the initial reaction velocity or the v naught for an enzyme catalyzed reaction. And looking at option a, it says that this initial reaction velocity v naught will actually increase when the pH increases. And of course, we know that this is definitely not true from our previous lesson videos on optimal enzyme conditions, and this is because we know that every enzyme is going to have a unique optimum pH. And so by increasing the pH, that does not necessarily mean that that will always lead to an increase in the initial reaction velocity because it's going to depend on the specific optimal pH for the enzyme that we're working with. And so for that reason, we can cross off option a because this is a false relationship. And so, moving on to the other options, notice that options b, c, and d are all indicating that the initial reaction velocity v naught is being limited by something. And so we know from our previous lesson videos that really what's limiting the initial reaction velocity is the v max, and we know that the v max acts as a horizontal asymptote to limit the initial reaction velocity. And so, if we change the v max, then we're changing what is limiting the initial reaction velocity. So anything that affects the v max, will also change what is limiting the initial reaction velocity. And so we already know clearly that the initial reaction velocity is limited by the substrate concentration, because when the substrate concentration is really really low, notice that the initial reaction velocity is limited. It's not able to, go to its maximal potential when the substrate concentration is low. So we can say that the substrate concentration does limit the substrate concentration does limit the initial reaction velocity, and so we can say that b here is a true relationship. And we also know that option c is true as well because it's saying that the initial reaction velocity is limited by the enzyme concentration. And again, in our last lesson video, we specifically said that the v max will change if we change the enzyme concentration. And so, by changing the enzyme concentration, we're changing the lit that, is limiting the initial reaction velocity. And so, again, we can say that, option c here is a true statement. And so looking at option d, it says that the initial reaction velocity is limited by the reaction's slowest step. So what do you guys think about this option? Is this option a true or a false statement? Well, what we need to look at is an enzyme catalyzed reaction, a typical enzyme catalyzed reaction, which is shown here. So you can see we have the free enzyme and the free substrate associating together via k one to form the enzyme substrate complex, and then, we have k two here, which shows the formation of the product. And, we also have k minus 1 that shows the breakdown for the reverse reaction here. And so, in this reaction, recall that we said specifically that k 2 is, always going to be assumed to be the slowest step of the reaction. And so, ultimately, the overall reaction that goes from substrate over to product, is only going to be able to go as fast as its slowest step. And the slowest step is also referred to as the rate limiting step. Recall that from your previous chemistry courses. And so really, what we can say is that this overall initial reaction rate, is going to be limited by the, slowest or the rate limiting reaction. And so because it is rate limiting, we can clearly see that the slowest step will be limiting the initial reaction velocity. And so what we can say is that d here is also true. And so because b, c, and d are true answers for this problem, we can say that it's actually f that indicates b, c, and d are, all true is the correct answer for this problem. And so, that concludes this practice problem and I'll see you guys in our next video.

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1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

6. Enzymes and Enzyme Kinetics

Vmax Enzyme

Biochemistry

6. Enzymes and Enzyme Kinetics

Vmax Enzyme

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Multiple Choice

V₀ for an enzyme-catalyzed reaction:

Increases when pH increases.

Is limited by the [S].

Is limited by the [E].

Is limited by the reaction's slowest step.

b & c.

b, c & d.

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Verified step by step guidance

Understand that V0 refers to the initial velocity of an enzyme-catalyzed reaction, which is the rate of reaction when the substrate concentration is much greater than the enzyme concentration.

Recognize that the initial velocity (V0) is influenced by the concentration of substrate ([S]) and enzyme ([E]). As [S] increases, V0 increases until it reaches a maximum velocity (Vmax) where all enzyme active sites are saturated.

Acknowledge that V0 is also limited by the concentration of enzyme ([E]) because the reaction cannot proceed faster than the number of available enzyme molecules to catalyze the reaction.

Consider the concept of the rate-limiting step, which is the slowest step in a reaction pathway. This step determines the overall rate of the reaction, thus limiting V0.

Conclude that V0 is limited by [S], [E], and the reaction's slowest step, making the correct answer b, c, and d.