The roles of ATP and phosphocreatine in muscle contraction
Muscles need ATP to contract. They store a backup molecule called phosphocreatine, which rapidly rebuilds ATP when supplies run low during exercise.
Formula
Phosphocreatine + ADP → Creatine + ATP
Real World
Creatine supplements used by sprinters like Dina Asher-Smith work by increasing phosphocreatine stores in muscles, allowing faster ATP regeneration during the first 8–10 seconds of explosive effort.
Exam Focus
Name all three ATP roles: myosin head detachment, myosin head re-cocking (hydrolysis), and active transport of Ca²⁺ back into the sarcoplasmic reticulum.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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