250+ TOP MCQs on Fundamentals – Enzyme Inhibition – 1 and Answers

Enzyme Technology Multiple Choice Questions on “Fundamentals – Enzyme Inhibition – 1”.

1. Substances which reduce the rate of enzyme catalyzed reactions are known as ____________
A. substrates
B. enzymes
C. products
D. inhibitors
Answer: D
Clarification: Certain substances may reduce the rate of enzyme catalyzed reactions. Some of these are non-specific protein denaturants (e.g., ureA.. While other substances which act in a fairly specific manner are referred to as inhibitors. Enzymes are biocatalyst which act on substrates to form products.

2. In the following diagram, which kind of inhibition is represented?

A. Uncompetitive inhibition
B. Competitive inhibition
C. Non-competitive inhibition
D. Mixed inhibition
Answer: B
Clarification: In the above diagram, it is shown that both substrate and inhibitor compete for the active site of the enzyme with formation of enzyme-inhibitor [EI] complex rather than enzyme-substrate-inhibitor [ESI] complex. Hence the inhibition shown in the diagram is competitive inhibition. It usually occurs at low substrate concentrations, but can be overcome at high substrate concentration.

3. The following rate equation represents _____________ inhibition.
(V=frac{V_{max} [S]}{K_m (1+frac{I}{K_i})+[S]})
A. competitive
B. mixed
C. non-competitive
D. uncompetitive
Answer: A
Clarification: Competitive inhibition occurs when both substrate and inhibitor compete for binding to the active site of the enzyme. In this kind of inhibition, K_i is much greater than total inhibitor concentration and ESI complex is not formed. This kind of inhibition is mostly seen when the substrate concentration are low. This inhibition can be overcome at sufficiently high substrate concentrations as V_max remain unaffected. Hence the rate equation is represented by (V=frac{V_{max} [S]}{K_m (1+frac{I}{K_i})+[S]})
Where,
K_m = Miachelis Menton constant, K_i = inhibitor constant, I = Inhibitor concentration and S = Substrate concentration.

4. Uncompetitive inhibition is most noticeable at low substrate concentration and can be overcome at high substrate concentration.
A. True
B. False
Answer: B
Clarification: Uncompetitive inhibitions occurs during multi-substrate reactions where the inhibitor is competitive to one substrate and uncompetitive to the other. These inhibition occur when one substrate is already bound to the enzyme. K_i is much greater than the total inhibitor concentration and EI complexes are not formed. Hence the above statement is false. This is true in case of competitive inhibition.

5. Inhibition of invertase by sucrose falls into which category of inhibition?
A. Substrate inhibition
B. Non-competitive inhibition
C. Product inhibition
D. Competitive inhibition
Answer: A
Clarification: Invertase inhibition by sucrose is kind of substrate inhibition. It is a special case of uncompetitive inhibition which occurs at high substrate concentrations. Product inhibition is case of competitive inhibition wherein the substrate and the inhibitor have structural similarity. Competitive inhibition is one wherein the substrate and the inhibitor compete for the active site of the enzyme. Non-competitive inhibition occurs when the inhibitor binds at the site away from the binding site, causing a reduction in catalytic activity.

6. ______________ inhibition represent the following rate equation.
(V=frac{left (frac{V_{max}}{1+frac{[I]}{K_i}}right )[S]}{K_m+[S]})
A. Substrate inhibition
B. Competitive inhibition
C. Product inhibition
D. Non-competitive inhibition
Answer: D
Clarification: Non-competitive inhibition is a special case of mixed inhibition. This kind of inhibition occurs when the inhibitor binds to the enzyme, far away from the catalytic site. In this case both EI and ESI complexes are equally formed. Hence the rate equation is given by the equation
(V=frac{left (frac{V_{max}}{1+frac{[I]}{K_i}}right )[S]}{K_m+[S]})

Where,
K_m = Miachelis Menton constant, K_i = inhibitor constant, I = Inhibitor concentration and S = Substrate concentration.