[Campbell Biology P.231] A glucose-fed yeast cell is transferred from an aerobic environment... | Practice Question

A glucose-fed yeast cell is transferred from an aerobic environment to an anaerobic one. If the cell needs to generate ATP at the same rate, how would its rate of glucose consumption change, and why?

  • A: It would increase, because anaerobic respiration (fermentation) is less efficient at producing ATP per glucose molecule than aerobic respiration.
  • B: It would decrease, because anaerobic respiration is more efficient at producing ATP.
  • C: It would remain the same, as ATP production rate is constant.
  • D: It would decrease initially, then increase, due to metabolic shock.

Explanation

The text states that 'To make the same amount of ATP, a facultative anaerobe has to consume sugar at a much faster rate when fermenting than when respiring.' This is because fermentation the anaerobic pathway yeast uses produces far less ATP per molecule of glucose than aerobic respiration. Therefore, to compensate for the lower efficiency and maintain the same ATP output, the cell must increase its rate of glucose consumption.