During the respiratory chain of cellular respiration, cytochrome c oxidizes:

Explanation

During the respiratory chain of cellular respiration, cytochrome c oxidizes cytochrome a₃. Cytochrome c acts as an electron carrier, transferring electrons from complex III to complex IV, where cytochrome a₃ is located. In this process, cytochrome c itself is oxidized as it donates electrons, and cytochrome a₃ is reduced. This step is crucial because it allows electrons to continue down the chain and ultimately reduces oxygen to water at the end of the respiratory chain. Cytochrome c does not oxidize oxygen directly, nor does it act on NADH or FADH₂, which serve as earlier electron donors in the chain.