Which of the following is a product of the Krebs cycle?

• A. Oxygen
• B. Glucose
• C. ATP
• D. NADH

Answer: (D)

Verified step by step guidance

1. Begin by understanding the Krebs cycle, also known as the citric acid cycle, which is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide.
2. Identify the main products of the Krebs cycle. The cycle produces several key molecules: carbon dioxide (CO₂), ATP, NADH, and FADH₂. These are generated through a series of enzymatic reactions.
3. Focus on NADH, which is one of the primary products of the Krebs cycle. NADH is produced when NAD⁺ is reduced during the cycle. This occurs in several steps, notably when isocitrate is converted to α-ketoglutarate and when α-ketoglutarate is converted to succinyl-CoA.
4. Understand the role of NADH in cellular respiration. NADH acts as an electron carrier, transporting electrons to the electron transport chain where it contributes to the production of ATP.
5. Review why the other options are not products of the Krebs cycle: Oxygen is used in the electron transport chain, not produced in the Krebs cycle; Glucose is broken down in glycolysis, not produced in the Krebs cycle; ATP is produced in small amounts directly in the Krebs cycle, but NADH is a more significant product.