Substrate-level phosphorylation is utilized to create ATP in which steps of aerobic cellular respiration?

• A. Electron Transport Chain and Chemiosmosis.
• B. Glycolysis and Pyruvate Oxidation.
• C. Pyruvate Oxidation and Krebs cycle.
• D. Glycolysis and Krebs cycle.

Answer: (D)

Verified step by step guidance

1. Understand that substrate-level phosphorylation is a process of ATP generation that occurs directly in the metabolic pathway by transferring a phosphate group to ADP from a phosphorylated intermediate.
2. Recall that aerobic cellular respiration consists of several stages: Glycolysis, Pyruvate Oxidation, Krebs Cycle (Citric Acid Cycle), and Electron Transport Chain with Chemiosmosis.
3. Identify that substrate-level phosphorylation occurs in the cytoplasm during Glycolysis and in the mitochondrial matrix during the Krebs Cycle.
4. Note that in Glycolysis, substrate-level phosphorylation occurs when a phosphate group is transferred from 1,3-bisphosphoglycerate to ADP, forming ATP and 3-phosphoglycerate.
5. Recognize that in the Krebs Cycle, substrate-level phosphorylation occurs when a phosphate group is transferred from succinyl-CoA to ADP (or GDP), forming ATP (or GTP) and succinate.