Enzymes and their role — NEET & JEE Questions

Question 1 · difficulty L1 · recall

Enzymes are primarily

• A. biological catalysts
• B. structural lipids
• C. storage carbohydrates
• D. inorganic salts only

Question 2 · difficulty L2 · understanding

Enzymes speed reactions mainly by

• A. lowering activation energy
• B. increasing the overall reaction enthalpy
• C. changing equilibrium constants permanently
• D. being consumed stoichiometrically

Question 3 · difficulty L2 · understanding

The region of an enzyme where substrate binds is called the

• A. active site
• B. ribosome
• C. nucleus
• D. cell wall

Question 4 · difficulty L2 · understanding

Enzyme specificity means that an enzyme

• A. acts preferentially on particular substrates or reactions
• B. catalyses every biochemical reaction
• C. never binds any substrate
• D. must be consumed after one reaction

Question 5 · difficulty L3 · application

Why can an enzyme be reused after catalysing a reaction?

• A. It is regenerated after the catalytic cycle
• B. It is converted permanently into product
• C. It is not involved in the reaction mechanism
• D. It becomes substrate

Question 6 · difficulty L3 · application

A substrate binds to an enzyme active site to form an enzyme-substrate complex. What is the main role of this complex?

• A. It facilitates conversion of substrate to product along a lower-energy pathway
• B. It permanently destroys the enzyme
• C. It raises activation energy
• D. It prevents all molecular collisions

Question 7 · difficulty L3 · application

Which statement about enzymes and equilibrium is correct?

• A. They speed both forward and reverse reactions but do not change the equilibrium position
• B. They make equilibrium constants larger in every case
• C. They force reactions to completion
• D. They change product free energies

Question 8 · difficulty L3 · application

An enzyme is highly specific for substrate S but not a very similar molecule T. The best explanation is

• A. the active site complements S more effectively in shape and interactions
• B. T has no atoms
• C. the enzyme has no active site
• D. specificity is unrelated to structure

Question 9 · difficulty L4 · application

A reaction is thermodynamically favourable but extremely slow. Adding the appropriate enzyme increases rate. Which quantity is primarily reduced?

• A. Activation energy
• B. Overall $\Delta G$
• C. Equilibrium constant
• D. Final product energy

Question 10 · difficulty L4 · application

Which statement best explains why enzymes can show very high catalytic efficiency?

• A. They orient substrates and stabilise transition states
• B. They increase product enthalpy
• C. They remove conservation of energy constraints
• D. They make all reactions diffusion-free