A muscle cell requires large amounts of energy during exercise. Explain why muscle cells contain many mitochondria and describe how oxygen and glucose are used inside these organelles during aerobic respiration.

Muscle cells contain many mitochondria because aerobic respiration, the main source of ATP during exercise, takes place in the mitochondria. The greater the number of mitochondria, the greater the capacity for aerobic respiration and therefore the larger amount of energy that can be released.

During aerobic respiration glucose is oxidised inside the mitochondria with oxygen as the final electron acceptor. The process produces carbon dioxide and water as the main end‑products, releasing energy that is stored in ATP.