Enzymes: Practice Questions

Which statement correctly describes how an enzyme increases the rate of a biochemical reaction?

A student investigated the effect of temperature on the rate of starch hydrolysis by amylase. The time taken for the starch to disappear at different temperatures was recorded.
At \(20^{\circ}\text{C}\), the time taken was \(120\text{ seconds}\).
At \(30^{\circ}\text{C}\), the time taken was \(40\text{ seconds}\).
How much faster is the rate of reaction at \(30^{\circ}\text{C}\) compared to \(20^{\circ}\text{C}\)?

An investigation into an enzyme-catalysed reaction reveals that the addition of a specific inhibitor leads to a decrease in the maximum reaction rate ($$V_{max}$$) but does not affect the Michaelis-Menten constant ($$K_m$$). Based on these observations, what type of inhibition is most likely occurring?

Enzyme specificity is best explained by which characteristic?

A competitive inhibitor affects an enzyme-catalysed reaction by:

Outline the lock-and-key and induced-fit hypotheses for enzyme action, and explain how a non-competitive inhibitor can reduce the rate of an enzyme-catalysed reaction.

The Michaelis-Menten constant (\(K_m\)) is a key parameter used to describe the properties of an enzyme.

(a) Define the term \(V_{max}\) and explain why the rate of an enzyme-catalysed reaction reaches this maximum value even if more substrate is added.
(b) Explain the relationship between the value of \(K_m\) and the affinity of an enzyme for its substrate, and state how this relationship is useful when comparing different enzymes that catalyse the same reaction.

Enzymes are highly specific biological catalysts.

(a) Explain the concept of enzyme specificity with reference to the active site and substrate.

(b) Compare and contrast the lock-and-key hypothesis and the induced-fit hypothesis regarding enzyme-substrate binding.