Enzyme Active Site and Induced Fit Model

Steps:

• Statement 1 is correct: Enzymes possess an active site, a specific surface region where the substrate binds via complementary shapes.
• Statement 2 is correct: In the induced fit model, both enzyme and substrate undergo slight, temporary shape changes to optimize binding and catalysis.
• Statement 3 is incorrect: Enzymes do not permanently change shape; they revert to their original conformation after the reaction, releasing products.
• Therefore, only statements 1 and 2 accurately describe enzyme action, selecting option B.

Why B is correct:

• Aligns with the lock-and-key and induced fit models, where active site binding (1) and reversible shape adjustments (2) enable catalysis without permanent alteration.

Why the others are wrong:

• A includes 3, but permanent shape change violates enzyme reusability.
• C excludes 1, yet active sites are fundamental to all enzyme function.
• D selects only 3, which misrepresents the temporary nature of enzyme-substrate interactions.

Final answer: B