Answer:
Correct answer is c. It is the final electron acceptor in the aerobic respiration.
Explanation:
Oxygen is a substrate of the aerobic respiration, but it is not the only one. Glucose is also a substrate.
Oxygen is used in the cells to be the final electron acceptor, this means that receives the electrons from NADH and FADH2. That is why, when there is no oxygen available for aerobic respiration, the NADH and FADH2 cannot be oxidized and therefore remain in their reduced form. As a consequence, they cannot be re-utilized during different cellular processes that are NAD+ and FAD dependant, such as glycolysis, pyruvate oxidation and cellular respiration. This means that the ATP synthesis stops.
Oxygen itself does not transport any electrones, this are transported by the cytochrome complex in the mitochondrial membrane. But oxygen is key in receiving those electrones, therefore a very important piece of the electron transport across the mitochondria.
