During the initial seconds of intense sprinting, muscle ATP concentration is maintained nearly constant despite a sharp rise in ATP consumption. The reaction primarily responsible transfers a phosphoryl group from a stored high-energy compound directly to ADP. That stored compound is:

• A Phosphoenolpyruvate
• B Creatine phosphate ✓
• C Glucose 6 phosphate
• D 1,3-bisphosphoglycerate

Explanation

Creatine kinase rapidly transfers the phosphoryl group of creatine phosphate to ADP, regenerating ATP within seconds of contraction onset. Muscle contains far more creatine phosphate than ATP itself, making it the immediate energy buffer before glycolysis accelerates. Phosphoenolpyruvate and 1,3-bisphosphoglycerate are transient glycolytic intermediates that participate in substrate-level phosphorylation but are never stored in appreciable amounts, so they cannot serve as an instant reserve the way creatine phosphate does.

Reference: Lippincott Biochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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