In oxidative phosphorylation, when $N^{+}AD$ becomes $NADH$, which process is occurring?

• A. $N^{+}AD$ is being hydrolyzed to release inorganic phosphate.
• B. $N^{+}AD$ is being reduced by gaining a hydride equivalent (electrons).
• C. $N^{+}AD$ is being oxidized by losing electrons.
• D. $N^{+}AD$ is being phosphorylated by ATP synthase.

Answer: (B)

Verified step by step guidance

1. Identify the molecules involved: NAD\(\textsuperscript{+}\) (nicotinamide adenine dinucleotide) and NADH. NAD\(\textsuperscript{+}\) is the oxidized form, and NADH is the reduced form.
2. Understand the chemical change: NAD\(\textsuperscript{+}\) becomes NADH by gaining electrons in the form of a hydride ion (H\(\textsuperscript{-}\)), which includes two electrons and one proton.
3. Recall the definition of oxidation and reduction: Oxidation is the loss of electrons, and reduction is the gain of electrons.
4. Apply this to the reaction: Since NAD\(\textsuperscript{+}\) gains electrons to form NADH, it is undergoing reduction.
5. Conclude that in oxidative phosphorylation, the conversion of NAD\(\textsuperscript{+}\) to NADH represents a reduction process where NAD\(\textsuperscript{+}\) accepts electrons (a hydride equivalent).