This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following biochemical reaction is associated with substrate level phosphorylation? 
Select and explain. 
A. Fumarate to malate, B. Succinate to fumarate, C. Succinyl CoA to Succinate, D. Acetoacetate to a-ketoglutarate
C: Succinyl CoA to Succinate
Answer: C: Succinyl CoA to Succinate 
Explanation: Conversion of succinyl CoA to succinate is an example of substrate level phosphorylation in which a high energy phosphate is generated from the energy trapped in the thioester bond of succinyl CoA. Enzyme succinic thiokinase catalyses this step. In this reaction a molecule of GDP is phosphorylated into GTP and succinate is formed. GTP so formed is conveed into ATP by reacting with an ADP molecule. Ref: Lippincott's Biochemistry, 2nd Edition, Page 109; Textbook of Biochemistry By D M Vasudevan, 3rd Edition, Pages 75-77, 194, 204