During muscle contraction

Options

A. Chemical energy is changed into electrical energy
B. Chemical energy is changed into mechanical energy
C. Chemical energy is changed into physical energy
D. Mechanical energy is changed into chemical energy

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Contraction:**
- Muscle contraction involves the shortening of muscle fibers, which allows for movement. This process requires energy.

2. **Energy Source:**
- The primary source of energy for muscle contraction is ATP (adenosine triphosphate). ATP is a molecule that stores and provides energy for various cellular processes.

3. **Energy Conversion:**
- During muscle contraction, the chemical energy stored in ATP is converted into mechanical energy. This mechanical energy is what enables the muscles to contract and perform work, such as moving limbs.

4. **Evaluating the Options:**
- The question presents four options regarding the conversion of energy during muscle contraction:
1. Chemical energy changed into electrical energy.
2. Chemical energy changed into mechanical energy.
3. Chemical energy changed into physical energy.
4. Mechanical energy changed into chemical energy.

5. **Identifying the Correct Option:**
- Among the options, the correct statement is that chemical energy (from ATP) is changed into mechanical energy during muscle contraction. Therefore, option 2 is the correct answer.

6. **Conclusion:**
- The correct answer to the question is that during muscle contraction, chemical energy is converted into mechanical energy.

---