2. How does water form during cellular respiration?

A Oxygen is oxidized, losing electrons and gaining hydrogen ions.

B Oxygen is reduced, gaining electrons and hydrogen ions.

c Oxygen is reduced, losing electrons and gaining hydrogen ions,

D Oxygen is oxidized, gaining electrons and hydrogen ions.

B

Explanation:

During the Krebs cycle in the matrix of the mitochondria, H + ions are usually pumped to the intermembrane space creating a proton-motive force. This potential difference is harness by ATP synthase to make ATPs as the H + ions 'drain' back to the matrix of the mitochondria. As these H + get to the matrix, they ultimately reduce oxygen to water. In this reaction, oxygen also acts as the ultimate electron acceptor in the Krebs cycle accepting 4 electrons from NADPH / NADH (so these molecules can be recycled back as NAD + and NADP+).

4H⁺ + O₂ + 4 ⁻e → 2H₂O