JEE Main 2021 · 20 July · evening · Single correct · +4 / −1
Which one of the following statements is not true about enzymes?
- (a) Enzymes are non-specific for a reaction and substrate.
- (b) Almost all enzymes are proteins.
- (c) Enzymes work as catalysts by lowering the activation energy of a biochemical reaction.
- (d) The action of enzymes is temperature and pH specific.
Answer and solution
Answer (a) Enzymes are non-specific for a reaction and substrate.
Solution
Chemistry ma’am · 2 steps
Enzymes are famous for being choosy, so the statement calling them non-specific is the false one.
- What specificity means. An enzyme has an active site shaped to fit one substrate, or a small group of very similar ones. Each enzyme catalyses one particular reaction, like a lock that opens for only one key.
Statement True or false Reason (a) Non-specific False Enzymes are highly specific for both the reaction and the substrate (b) Almost all are proteins True Most enzymes are globular proteins; a few catalytic RNAs (ribozymes) are the exceptions (c) Lower activation energy True They give the reaction an easier path with a lower energy barrier, so it goes faster (d) Temperature and pH specific True Each enzyme works best at an optimum temperature and pH, and too much heat or a wrong pH denatures it - So. The statement that is not true is (a): enzymes are specific, not non-specific.
The idea to keep. Remember the enzyme checklist: mostly proteins, highly specific, lower the activation energy, and work best at an optimum temperature and pH. Read NOT questions twice.
Answer from the NTA final answer key. Solution by PrepWiser.