For each molecule of glucose completely respired, the total number of carbon dioxide molecules released is

  • A. 2
  • B. 4
  • C. 6
  • D. 8

Explanation

Two CO2 come from the oxidative decarboxylation of the two pyruvate molecules and four from the two turns of the Krebs cycle, giving six in all. Glycolysis releases none, which is why the link reaction and Krebs account for every CO2 breathed out.

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