Enzyme kinetics at low substrate concentration

Steps:

• Apply Michaelis-Menten equation: v = Vmax [S] / (Km + [S]).
• At low [S] << Km, approximate v ≈ (Vmax/Km) [S].
• In competition, substrate partitioning depends on relative Vmax/Km values.
• Without Km data, Vmax alone cannot predict substrate usage.

Why D is correct:

• Not enough information; substrate usage depends on Km, not just Vmax.

Why the others are wrong:

• A: Usage unequal unless Vmax/Km identical.
• B: Enzymes function at low [S] via diffusion and binding.
• C: Lower Vmax may increase or decrease usage depending on Km.

Final answer: Not enough information.