Question

Enzymes are needed only in small quantities to catalyse reactions because

• A. they act very fast.
• B. they remain unchanged at the end of the reaction.
• C. they are made up to proteins.
• D. they are temperature and pH sensitive.

Hint:

Key idea: Enzymes = Reusable catalysts 1 enzyme $\rightarrow$ many reactions

Answer 1

The Correct Option is B

Concept: Enzymes are biological catalysts that speed up chemical reactions without being consumed.
• They lower activation energy.
• They are not permanently altered during the reaction.
• One enzyme molecule can catalyse many reactions repeatedly.

Step 1: Understand catalytic nature.
Enzymes participate in reactions but are regenerated after each cycle.

Step 2: Reason for small quantity.
Since enzymes are not used up, a small amount can catalyse large amounts of substrate.

Step 3: Analyze options.
• (A) Fast action: True but not the main reason
• (B) Remain unchanged: Correct reason
• (C) Protein nature: Irrelevant
• (D) Sensitivity: Not related

Step 4: Conclusion.
Thus, enzymes are required in small quantities because they are not consumed. Final Answer: Option (B)