Which of the following statements about the ATP-CP energy system is true?

• A. The phosphate group is cleaved from ATP, binding to creatine & regenerating CP.
• B. The phosphate group is cleaved from CP, binding to ADP & regenerating ATP.
• C. When a phosphate group binds to ADP (regenerating ATP), it releases energy.
• D. All of the above are true.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the ATP-CP energy system. This system is also known as the phosphagen system and is used for short bursts of high-intensity activity. It relies on stored creatine phosphate (CP) to regenerate ATP quickly.
2. Step 2: Recall the chemical process involved. ATP (adenosine triphosphate) is the primary energy currency of the cell. When energy is needed, ATP is broken down into ADP (adenosine diphosphate) and a phosphate group, releasing energy.
3. Step 3: Examine the role of creatine phosphate (CP). CP donates its phosphate group to ADP, regenerating ATP. This process does not release energy directly but allows ATP to be replenished for immediate use.
4. Step 4: Analyze the statements provided. The correct statement is: 'The phosphate group is cleaved from CP, binding to ADP & regenerating ATP.' This describes the key mechanism of the ATP-CP energy system.
5. Step 5: Evaluate the other statements. The statement 'The phosphate group is cleaved from ATP, binding to creatine & regenerating CP' is incorrect because ATP is not used to regenerate CP. The statement 'When a phosphate group binds to ADP (regenerating ATP), it releases energy' is also incorrect because energy is released when ATP is broken down, not regenerated.