Question

In TCA cycle substrate level phosphorylation takes place during the conversion of

• A. oxaloacetic acid to citric acid
• B. succinyl Co-A to succinic acid
• C. succinic acid to fumaric acid
• D. fumaric acid to malic acid

Answer 1

Answer: (B)

succinyl Co-A to succinic acid

Answer 2

Tricarboxylic acid cycle or citric acid cycle or Krebs cycle takes place in matrix of mitochondria. Acetyl coenzyme-A is connecting link between cycle and EMP pathway, while oxaloacetate is acceptor molecule. Substrate level phosphorylation takes place during the conversion of succinyl Co-A to succinic acid,
Succinyl Co-A + ADP + $H_{3}PO_{4} \xrightarrow[Co-A\, \text{synthetase}]{\text{Succinyl}}$ succinic acid + ATP + Co-A