The graph shows the rate of an enzyme-catalysed reaction at increasing substrateconcentrations.At which of the following point(s) do all active sites of the enzyme seem occupied?
Correct answer: D. Points II and III
- A. Point I only
- B. Point III only
- C. Points I and II
- D. Points II and III
Explanation
The rate of an enzyme-catalyzed reaction increases with substrate concentration until all enzyme active sites are occupied, at which point the reaction reaches a maximum rate and plateaus. This is known as Vmax. At Point II and Point III on the graph, the substrate concentration is sufficiently high to ensure that all active sites are occupied, indicating the reaction is at or near Vmax. Point I, however, likely represents a lower substrate concentration where not all active sites are occupied. Thus, the correct answer is Points II and III.
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About Factors Affecting Enzyme Action
Enzyme activity changes with temperature, pH, substrate concentration and enzyme concentration because these factors affect molecular collisions and the active site. Questions also examine optimum conditions, denaturation and inhibition, while distinguishing a fall in activity caused by unsuitable conditions from permanent enzyme damage.
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