Question

NAD\(^+\) in cellular respiration acts as ______________

• A. A source for ATP synthase
• B. An enzyme
• C. An electron carrier
• D. An electron acceptor for anaerobic respiration

Hint:

Think of NAD\(^+\)/NADH as a reusable shuttle bus for electrons. It picks up high-energy electrons during glycolysis and the Krebs cycle, and drops them off at the Electron Transport Chain to generate ATP.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Respiration is a metabolic process that oxidizes organic molecules (like glucose) to extract energy.
During this process, hydrogen atoms (electrons and protons) are removed from the substrate and transferred through a series of intermediate molecules to a final electron acceptor.

Step 2: Detailed Explanation:
Let us analyze the role of Nicotinamide Adenine Dinucleotide (NAD\(^+\)) in cellular respiration:
- NAD\(^+\) is a coenzyme found in all living cells.
- During glycolysis, the link reaction, and the Krebs cycle, dehydrogenase enzymes oxidize the respiratory substrate by removing two hydrogen atoms (equivalent to two protons and two electrons).
- NAD\(^+\) accepts these electrons along with one proton, reducing it to NADH:
\[ \text{NAD}^+ + 2\text{H}^+ + 2\text{e}^- \rightarrow \text{NADH} + \text{H}^+ \] - NADH then transports these high-energy electrons to the Electron Transport Chain (ETC) on the inner mitochondrial membrane, where it is oxidized back to NAD\(^+\):
- The energy released from these electrons as they move through the ETC is used to generate a proton gradient that drives ATP synthesis.
- Therefore, NAD\(^+\) acts as a dynamic, mobile electron carrier that couples the oxidation of metabolic intermediates with the synthesis of ATP.

Step 3: Final Answer:
The correct option is (C).