Evaluating Enzyme Statements

Steps:

• Statement 1 is correct: Enzymes are proteins that lower activation energy as biological catalysts.
• Statement 2 is incorrect: Enzymes remain unchanged and reusable after catalyzing reactions.
• Statement 3 is correct: The lock-and-key hypothesis describes specific enzyme-substrate binding like a lock fitting a key.
• Thus, only statements 1 and 3 are accurate, matching option C.

Why C is correct:

• C selects statements 1 and 3, aligning with the biochemical definition of enzymes as unaltered protein catalysts and the specificity of the lock-and-key model.

Why the others are wrong:

• A includes false statement 2, as enzymes are not permanently altered.
• B includes false statement 2, ignoring enzyme reusability.
• D excludes true statement 1, misrepresenting enzyme composition.

Final answer: C