Explain why Culture Y consumed more glucose than Culture X, and what this implies about the metabolic efficiency of the cultures.

a) Culture Y consumed more glucose than Culture X because Culture Y performs anaerobic respiration due to low oxygen concentration, which is a much less efficient process for ATP production compared to the aerobic respiration performed by Culture X. To produce a smaller amount of ATP (24 units), Culture Y had to break down a larger quantity of glucose (40 mg) compared to Culture X, which produced significantly more ATP (72 units) from less glucose (18 mg).

b) This suggests that the metabolic pathway used by Culture Y (anaerobic respiration/fermentation) is inefficient in terms of ATP production per unit of glucose consumed. It yields significantly less energy (ATP) from the same amount of glucose compared to aerobic respiration.