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Multiple Choice
As glucose is oxidized during cellular respiration, the coenzyme NAD$^+$ accepts two electrons and is:
A
converted to FADH$_2$
B
hydrolyzed to ADP
C
oxidized to NADH$_2$
D
reduced to NADH
Verified step by step guidance
1
Understand the role of NAD$^+$ in cellular respiration: NAD$^+$ is a coenzyme that acts as an electron carrier during the process of cellular respiration. It plays a critical role in transferring electrons from one molecule to another.
Recall the concept of oxidation and reduction: Oxidation involves the loss of electrons, while reduction involves the gain of electrons. In this case, NAD$^+$ gains electrons during cellular respiration.
Examine the chemical change: NAD$^+$ accepts two electrons and one proton (H$^+$), which reduces it to NADH. This is a reduction reaction because NAD$^+$ gains electrons.
Compare NADH with other molecules mentioned in the options: FADH$_2$ is another electron carrier, but it is not formed directly from NAD$^+$. ADP is a product of ATP hydrolysis, unrelated to NAD$^+$. NADH$_2$ is not a correct term; NADH is the proper reduced form of NAD$^+$.
Conclude that NAD$^+$ is reduced to NADH during cellular respiration, as it gains electrons and a proton in the process.