Enzymes | Biology | Target Mdcat 2025

Question 1

Who first coined the term 'enzyme'?

Payen

Kühne

Persoz

Fischer

Question 2

Which of the following pairs is incorrectly matched?

Diastase – First enzyme discovered

Emil Fischer – Lock and key model

Koshland – Induced fit model

Payen – Term 'enzyme' coined

Question 3

Enzymes accelerate biochemical reactions mainly by:

Lowering activation energy

Increasing free energy of products

Changing substrate concentration

Altering equilibrium constant

Question 4

The specificity of sucrase as compared to carbonic anhydrase is:

Lower

Equal

Higher

Non-comparable

Question 5

The inactive protein part of an enzyme without a cofactor is called:

Prosthetic group

Apoenzyme

Holoenzyme

Coenzyme

Question 6

Which of the following is a correct holoenzyme example?

Hemoglobin without Fe²⁺

Carbonic anhydrase + Zn²⁺

Apoenzyme alone

Cofactor without enzyme

Question 7

Enzyme action can be best described as:

Irreversible change of substrate and enzyme

Enzyme consumed in the reaction

Enzyme remains unchanged after reaction

Enzyme lowers substrate concentration permanently

Question 8

According to Emil Fischer’s model, the active site of an enzyme is:

Rigid and specific

Flexible and adaptable

Destroyed after reaction

Similar for all enzymes

Question 9

The limitation of lock and key model is that it:

Explains enzyme flexibility

Cannot explain allosteric regulation

Shows induced fit

Explains reversible inhibition

Question 10

The induced fit model was proposed in:

1878

1894

1959

1970

Question 11

In induced fit model, after product release, the enzyme:

Becomes permanently deformed

Returns to original shape

Loses its activity

Remains bound to substrate

Question 12

Which enzyme’s activity is a good example of induced fit?

Sucrase

Pepsin

Hemoglobin binding O₂

Salivary amylase

Question 13

Which enzyme can function at -10°C?

Human amylase

Thermophilic enzyme

Arctic snow flea enzyme

Catalase

Question 14

Thermophilic bacteria enzymes are most active around:

37°C

40°C

90°C

120°C

Question 15

At optimum temperature, enzyme activity is:

Zero

Maximum

Minimal

Irreversible

Question 16

If the pH of catalase is shifted from 7.6 to 2.0, what happens?

Activity increases

Activity decreases

Becomes permanently inactive

No effect

Question 17

Which enzyme has the highest optimum pH among the following?

Salivary amylase

Chymotrypsin

Pepsin

Arginase

Question 18

Slight change in pH usually:

Completely denatures enzyme

No effect

Converts holoenzyme to apoenzyme

Causes reversible loss of activity

Question 19

If enzyme concentration increases but substrate concentration is limiting, the reaction rate:

Decreases

Increases linearly

Reaches Vmax

Becomes zero

Question 20

The plateau in enzyme concentration vs velocity graph is due to:

Substrate saturation

Cofactor deficiency

Optimum pH

Competitive inhibition