9th class Biology, Chapter 6: Enzymes MCQs

1. Primarily, all enzymes are:

1. (A) Nucleic acids
2. (B) Proteins ✓
3. (C) Carbohydrates
4. (D) Lipids

2. Which best defines an enzyme?

1. (A) A chemical that breaks down food.
2. (B) A hormone that regulates metabolism.
3. (C) A protein that speeds up reactions. ✓
4. (D) A molecule that stores energy.

3. Enzymes are specific in their action because:

1. (A) Their active sites fit specific substrates. ✓
2. (B) They are always proteins.
3. (C) They are consumed in reactions.
4. (D) They work only at high temperatures.

4. Prosthetic groups are:

1. (A) Required by all enzymes.
2. (B) Proteins in nature.
3. (C) Loosely attached with enzymes.
4. (D) Tightly bound to enzyme. ✓

5. What is TRUE according to the induced fit model of enzyme action?

1. (A) Enzyme's active site changes shape to bind the substrate. ✓
2. (B) Substrate changes shape to bind to active site.
3. (C) No shape changes occur in active site or substrate.
4. (D) Substrate attaches the enzyme at a site other than active site.

6. The sum of all chemical reactions that occur within an organism to sustain life is called:

1. (A) metabolism ✓
2. (B) digestion
3. (C) respiration
4. (D) excretion

7. The breakdown of complex molecules into simpler ones with the release of energy is:

1. (A) catabolism ✓
2. (B) anabolism
3. (C) photosynthesis
4. (D) protein synthesis

8. Which of the following is an example of catabolism?

1. (A) Cellular respiration ✓
2. (B) Photosynthesis
3. (C) Protein synthesis
4. (D) Formation of starch

9. Lipolysis breaks lipids (fat) into:

1. (A) fatty acids and glycerol ✓
2. (B) amino acids
3. (C) glucose
4. (D) carbon dioxide and water

10. Anabolism is the process that:

1. (A) builds complex molecules from simpler ones using energy ✓
2. (B) breaks down food to release energy
3. (C) removes wastes
4. (D) produces no new molecules

11. Which of the following is an anabolic process?

1. (A) Protein synthesis ✓
2. (B) Cellular respiration
3. (C) Lipolysis
4. (D) Digestion of starch

12. Enzymes are biological ____ that speed up chemical reactions.

1. (A) catalysts ✓
2. (B) hormones
3. (C) vitamins
4. (D) pigments

13. Enzymes speed up reactions and are:

1. (A) not consumed in the process ✓
2. (B) used up in the reaction
3. (C) changed into products
4. (D) destroyed by the substrate

14. Typically an enzyme contains about:

1. (A) 100 to 1,000 amino acids ✓
2. (B) 10 amino acids
3. (C) 10,000 amino acids
4. (D) no amino acids

15. An RNA molecule that acts as an enzyme is called:

1. (A) ribozyme ✓
2. (B) coenzyme
3. (C) amylase
4. (D) cofactor

16. The enzyme amylase catalyses the breakdown of:

1. (A) starch into simple sugars ✓
2. (B) proteins into amino acids
3. (C) fats into fatty acids
4. (D) sugar into starch

17. Enzymes that operate within cells, such as those of cellular respiration, are:

1. (A) intracellular enzymes ✓
2. (B) extracellular enzymes
3. (C) coenzymes
4. (D) prosthetic groups

18. The enzymes secreted by cells of the stomach wall into the stomach cavity are:

1. (A) extracellular enzymes ✓
2. (B) intracellular enzymes
3. (C) cofactors
4. (D) ribozymes

19. Non-protein molecules needed by many enzymes to be fully active are called:

1. (A) cofactors ✓
2. (B) substrates
3. (C) products
4. (D) ribozymes

20. Which of the following is an inorganic cofactor?

1. (A) Iron ions ✓
2. (B) Biotin
3. (C) NAD
4. (D) Haem group