Which of the following is incorrect regarding muscle contraction?

Options

A. Actin and myosin make actomyosin.
B. Phosphate reserve comes from phosphocreatine.
C. Chemical energy is converted into mechanical energy.
D. Mechanical energy is converted into chemical energy.

Answer

To determine which statement regarding muscle contraction is incorrect, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Muscle Contraction**: Muscle contraction involves the interaction between two key proteins: actin and myosin. These proteins work together to enable muscle fibers to contract and produce movement.

2. **Evaluating the First Statement**:
- The first statement claims that "actin and myosin make ectomyosin."
- This statement is **correct** because ectomyosin is indeed a protein complex formed by the combination of actin and myosin.

3. **Evaluating the Second Statement**:
- The second statement states that "phosphate reserves come from phosphocreatine."
- This statement is also **correct**. Phosphocreatine serves as a reservoir for phosphate groups that can be used to regenerate ATP, which is essential for muscle contraction.

4. **Evaluating the Third Statement**:
- The third statement asserts that "chemical energy is converted into mechanical energy."
- This statement is **correct** as well. During muscle contraction, ATP (which contains chemical energy) is converted into mechanical energy, enabling muscle movement.

5. **Evaluating the Fourth Statement**:
- The fourth statement claims that "mechanical energy is converted into chemical energy."
- This statement is **incorrect**. In muscle contraction, it is the chemical energy (from ATP) that is converted into mechanical energy, not the other way around.

### Conclusion:
The incorrect statement regarding muscle contraction is the fourth option: "mechanical energy is converted into chemical energy."

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