Final answer:
The membranes of the mitochondrion must be crossed by pyruvate to be converted into acetyl CoA for the citric acid cycle, ultimately leading to ATP production in cellular respiration.
Step-by-step explanation:
The membranes of the mitochondrion must be crossed by pyruvate prior to its oxidation during respiration. During cellular respiration, pyruvate, which is the product of glycolysis, is transported into the mitochondria where it is converted to acetyl CoA. This conversion is essential for pyruvate to enter the citric acid cycle (or Krebs cycle), which occurs in the mitochondrial matrix. The acetyl CoA then enters the Krebs cycle where it is fully oxidized into carbon dioxide. Subsequently, the electrons from these reactions pass through the electron transport chain located on the inner mitochondrial membrane, resulting in the production of ATP through oxidative phosphorylation.