Why is the Krebs cycle necessary within cellular respiration?

• A. It breaks down glucose into pyruvate.
• B. It converts carbon dioxide into glucose.
• C. It generates electron carriers that are used in the electron transport chain.
• D. It produces ATP directly for cellular energy.

Answer: (C)

Verified step by step guidance

1. Begin by understanding the role of the Krebs cycle within cellular respiration. The Krebs cycle, also known as the citric acid cycle, 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. Recognize that the Krebs cycle is not directly involved in breaking down glucose into pyruvate. This process occurs during glycolysis, which is the first stage of cellular respiration.
3. Understand that the Krebs cycle does not convert carbon dioxide into glucose. Instead, it releases carbon dioxide as a waste product while processing acetyl-CoA.
4. Identify the primary function of the Krebs cycle: it generates electron carriers, specifically NADH and FADH2. These carriers are crucial for the electron transport chain, where they donate electrons to help produce ATP.
5. Note that while the Krebs cycle does produce a small amount of ATP directly, its main contribution to cellular energy production is through the generation of electron carriers that facilitate ATP synthesis in the electron transport chain.