Which chemical process generates the $\mathrm{ATP}$ produced in the citric acid cycle?

• A. Glycolysis
• B. Oxidative phosphorylation
• C. Substrate-level phosphorylation
• D. Photophosphorylation

Answer: (C)

Verified step by step guidance

1. Understand the context of the citric acid cycle, which is a key metabolic pathway that connects carbohydrate, fat, and protein metabolism.
2. Recognize that ATP production in the citric acid cycle occurs through substrate-level phosphorylation, a process where a phosphate group is directly transferred to ADP from a phosphorylated intermediate.
3. Differentiate substrate-level phosphorylation from oxidative phosphorylation, which occurs in the electron transport chain and involves the generation of ATP through a proton gradient.
4. Identify that glycolysis, another metabolic pathway, also involves substrate-level phosphorylation but is separate from the citric acid cycle.
5. Note that photophosphorylation is a process related to photosynthesis in plants and is not involved in the citric acid cycle.