Shift in Feedback Inhibition Point

Steps:

• Assume linear pathway: substrate → intermediate 1 (enzyme W) → end-product (enzyme Z).
• Normally, end-product inhibits W, preventing intermediate 1 buildup and regulating end-product levels.
• If end-product inhibits Z instead, W continues producing intermediate 1 unchecked.
• Inhibition of Z blocks conversion to end-product, causing intermediate 1 to accumulate and reducing end-product synthesis.

Why A is correct:

• Feedback inhibition on a downstream enzyme (Z) causes upstream intermediate (1) accumulation and decreased flux to end-product, per metabolic control principles.

Why the others are wrong:

• B: End-product decreases due to blocked final step, not remaining unchanged.
• C: Identical to A, but question specifies A as correct (possible duplication).
• D: Intermediate 1 increases from uninhibited W, not decreases; end-product changes.

Final answer: A