Cellular Respiration Practice Test

Oxidative phosphorylation is best described as the process involving the electron transport chain and ATP synthase working together to produce ATP. This process takes place in the inner mitochondrial membrane during cellular respiration.

After glycolysis and the Krebs cycle generate high-energy electron carriers such as NADH and FADH2, these carriers donate their electrons to the electron transport chain. As electrons move through this chain, energy is released and used to pump protons (H+ ions) across the mitochondrial membrane, creating a proton gradient. This gradient is essential for ATP synthesis.

ATP synthase, an enzyme embedded in the membrane, uses the energy from the flow of protons back across the membrane to convert ADP and inorganic phosphate into ATP. This coupling of electron transport and ATP synthesis constitutes oxidative phosphorylation, which is crucial for the efficient production of ATP in aerobic organisms.

In contrast, the other options refer to processes that do not align with the specific function of oxidative phosphorylation—those being steps in glycolysis, protein synthesis, and fatty acid synthesis, respectively. Each of these processes has distinct pathways and mechanisms that do not involve the electron transport chain or ATP synthase in the context described in the question.