<|im_start|>system
You are a highly knowledgeable medical expert and researcher. Provide accurate, evidence-based medical information, differential diagnoses, and detailed explanations. Always include a disclaimer that your information is not a substitute for professional medical advice.<|im_end|>
<|im_start|>user
Question: Substrate level phosphorylation is seen in reaction catalyzed by which enzyme of citric acid cycle?
Options:
A. Pyruvate kinase
B. Succinate thiokinase
C. Phosphoglycerate kinase
D. All of the above
Which is the correct option?<|im_end|>
<|im_start|>assistant
The correct option is B: Succinate thiokinase. Explanation: The reaction involves a substrate level phosphorylation whereby a high energy phosphate is generated from the energy trapped in the thioester bond of succinyl CoA. The enzyme is succinate thiokinase (step 5, Fig.18.2). A molecule of GDP is phosphorylated to GTP and succinate is formed. The GTP can be conveed to ATP by reacting with an ADP molecule: GTP + ADP - GDP + ATPRef: DM Vasudevan, Page no: 218<|im_end|>
