Which of the following best describes the correct sequence of major pathways in cellular respiration?

• A. Krebs cycle → Glycolysis → Electron transport chain
• B. Glycolysis → Electron transport chain → Krebs cycle
• C. Glycolysis → Krebs cycle → Electron transport chain
• D. Electron transport chain → Glycolysis → Krebs cycle

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the process of cellular respiration, which is the metabolic pathway that cells use to generate energy in the form of ATP. It consists of three major stages: Glycolysis, the Krebs cycle (also known as the citric acid cycle), and the Electron Transport Chain (ETC).
2. Step 2: Glycolysis is the first step in cellular respiration. It occurs in the cytoplasm and involves the breakdown of glucose into two molecules of pyruvate, producing a small amount of ATP and NADH. This step does not require oxygen.
3. Step 3: The pyruvate produced in glycolysis is transported into the mitochondria, where it enters the Krebs cycle. The Krebs cycle generates high-energy electron carriers (NADH and FADH2) and a small amount of ATP. This step occurs in the mitochondrial matrix.
4. Step 4: The high-energy electron carriers (NADH and FADH2) produced in the Krebs cycle are then used in the Electron Transport Chain, which is located in the inner mitochondrial membrane. Electrons are passed through a series of protein complexes, creating a proton gradient that drives ATP synthesis via oxidative phosphorylation.
5. Step 5: Based on the sequence of events described above, the correct order of major pathways in cellular respiration is: Glycolysis → Krebs cycle → Electron Transport Chain.