Final answer:
During the first 10 to 30 seconds of maximal activity, pyruvate is converted into Acetyl-S-Coenzyme A (Ac-S-CoA) in the mitochondria. This molecule is completely oxidized in the Krebs cycle, generating ATP, NADH, and FADH2. These high-energy molecules then contribute to the production of more ATP through the electron transport chain.
Step-by-step explanation:
During the first 10 to 30 seconds of maximal activity, the action that occurs within the mitochondria is the conversion of pyruvate into Acetyl-S-Coenzyme A (Ac-S-CoA), which is then completely oxidized in the Krebs cycle. The Krebs cycle generates high-energy molecules such as ATP, NADH, and FADH2. These molecules then pass electrons through the electron transport chain in the mitochondria, producing more ATP.