Matching enzyme reaction curves to concentration profiles

Steps:

• Locate the steadily increasing curve from zero: this is product formation.
• Find the overall decreasing curve starting high: this is substrate depletion.
• Identify the curve that rises sharply then declines: this is the transient enzyme-substrate complex.
• Spot the curve that initially drops then recovers to baseline: this is unbound enzyme adjusting to complex formation.

Why D is correct:

• D assigns product to the rising curve, unbound enzyme to the dip-recovery, substrate to the steady decline, and enzyme-substrate to the peak-then-fall, matching Michaelis-Menten kinetics where ES peaks mid-reaction.

Why the others are wrong:

• A mislabels unbound enzyme as the rising curve, ignoring its transient dip.
• B swaps product and enzyme-substrate, contradicting the complex's temporary rise.
• C places product on a non-increasing curve, violating product accumulation.

Final answer: D