Induced Fit Alters Enzyme Conformation

Steps:

• Induced fit hypothesis states enzymes change shape to fit substrate precisely.
• This change involves folding adjustments in the enzyme's 3D structure.
• Primary structure (amino acid sequence) remains fixed and unchanged.
• Secondary structure (local folds like alpha helices) typically stays intact, while tertiary (overall 3D shape) and quaternary (subunit interactions) adjust for binding.

Why D is correct:

• Induced fit requires dynamic shifts in tertiary (single-chain folding) and quaternary (multi-subunit assembly) structures to form the active site, as defined by Koshland's model.

Why the others are wrong:

• A: Includes primary (sequence), which never changes in induced fit.
• B: Focuses on primary and secondary, but these are stable and unaffected.
• C: Omits quaternary, which changes in multi-subunit enzymes like hemoglobin.

Final answer: D