Q5 / 200 · MHT CET - Medical 2026 (21 April Shift 1) · Biology
Substrate level phosphorylation occurs --------------------.
- Ain cytoplasm of the cells only.
- Bon the inner mitochondrial membrane.
- Cin matrix of mitochondria only.
- Correct answerDin cytoplasm of the cells and matrix of mitochondria.
Solution
Substrate level phosphorylation is the direct synthesis of ATP from ADP by the transfer of a phosphate group from a phosphorylated reactive intermediate.
During glycolysis, which takes place in the cytoplasm, substrate level phosphorylation occurs at two steps: the conversion of $1,3$-bisphosphoglycerate to $3$-phosphoglyceric acid and the conversion of phosphoenolpyruvate to pyruvic acid.
During the Krebs cycle, which takes place in the mitochondrial matrix, substrate level phosphorylation occurs during the conversion of succinyl-CoA to succinic acid, where a molecule of GTP (which is then used to form ATP) is synthesized.
Therefore, substrate level phosphorylation occurs in both the cytoplasm of the cells and the matrix of mitochondria.
Answer: in cytoplasm of the cells and matrix of mitochondria.
During glycolysis, which takes place in the cytoplasm, substrate level phosphorylation occurs at two steps: the conversion of $1,3$-bisphosphoglycerate to $3$-phosphoglyceric acid and the conversion of phosphoenolpyruvate to pyruvic acid.
During the Krebs cycle, which takes place in the mitochondrial matrix, substrate level phosphorylation occurs during the conversion of succinyl-CoA to succinic acid, where a molecule of GTP (which is then used to form ATP) is synthesized.
Therefore, substrate level phosphorylation occurs in both the cytoplasm of the cells and the matrix of mitochondria.
Answer: in cytoplasm of the cells and matrix of mitochondria.
Hence, the correct answer is option: 'D'.