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 statement provided in the question.

1. **Statement Analysis**:
- **Statement A**: "Ectin and myosin make ectomyosin."
- This statement is correct. Ectin (also known as actin) and myosin are the two primary contractile proteins in muscle fibers. They interact to form a complex called ectomyosin, which is essential for muscle contraction.

- **Statement B**: "Phosphate reserve comes from phosphocretin."
- This statement is also correct. Phosphocreatine (or creatine phosphate) serves as a reservoir for phosphate groups, which are used to regenerate ATP from ADP during muscle contraction, thus providing energy for muscle activity.

- **Statement C**: "Chemical energy is converted into mechanical energy."
- This statement is correct as well. During muscle contraction, the chemical energy stored in ATP is converted into mechanical energy, allowing muscles to perform work such as movement.

- **Statement D**: "Mechanical energy is converted into chemical energy."
- This statement is incorrect. Muscle contraction involves the conversion of chemical energy (from ATP) into mechanical energy, not the other way around. Therefore, this statement contradicts the established understanding of muscle physiology.

2. **Conclusion**:
- The incorrect statement regarding muscle contraction is **Statement D**: "Mechanical energy is converted into chemical energy."