Question

Which one of the following redox couples has the highest tendency to donate electrons?

• A. ( Fumarate / Succinate )
• B. ( NAD(^+) / NADH )
• C. ( FAD / FADH(_2)
• D. ( Pyruvate / Lactate )

Hint:

When evaluating the electron-donating ability of redox couples, consider both their roles in cellular processes and their electrochemical properties, including their standard reduction potentials.

Answer 1

The Correct Option is B

The tendency of a redox couple to donate electrons can be determined by their standard reduction potential. The more negative the standard reduction potential, the stronger the tendency of the reduced form to donate electrons. 
Overview of Redox Couples: Fumarate / Succinate: This couple involves the conversion of succinate to fumarate in the Krebs cycle, which does not have a strong tendency to donate electrons. 
NAD(^+) / NADH: Correct. NADH is a high-energy molecule that readily donates electrons in oxidative phosphorylation to drive ATP production, reflecting its strong electron-donating capability. 
FAD / FADH(_2): While FADH(_2) also donates electrons in the electron transport chain, its electron-donating ability is less potent compared to NADH. 
Pyruvate / Lactate: The conversion of lactate to pyruvate is also involved in metabolic processes but is not as potent a donor as NADH. Conclusion:
Explanation: NADH, derived from NAD(^+), has a significant role in cellular respiration, specifically in donating electrons to the electron transport chain. Its high energy and strong electron-donating capacity make it the most effective among the listed options.