In a sarcomere , the H - zone is paler than the rest of A-band because it consists of

Options

A. Only myosin filaments
B. Only actin filaments
C. both actin and filaments
D. filaments are absent

Answer

To solve the question regarding why the H-zone in a sarcomere is paler than the rest of the A-band, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Sarcomere Structure**:
- A sarcomere is the basic contractile unit of muscle tissue. It consists of various bands and zones, including the A-band, I-band, and H-zone.

2. **Identifying the A-band**:
- The A-band is the dark band of the sarcomere and contains both thick filaments (myosin) and thin filaments (actin). This combination gives the A-band a darker appearance.

3. **Understanding the H-zone**:
- The H-zone is a lighter region located in the center of the A-band. It is the area where only thick filaments (myosin) are present without any overlapping thin filaments (actin).

4. **Color Comparison**:
- Since the H-zone consists solely of myosin filaments, it appears paler compared to the A-band, which contains both myosin and actin filaments. The absence of actin in the H-zone results in a lighter color.

5. **Conclusion**:
- Therefore, the H-zone is paler than the rest of the A-band because it consists only of myosin filaments, while the A-band contains both myosin and actin filaments.

### Final Answer:
The H-zone is paler than the rest of the A-band because it consists solely of myosin filaments, whereas the A-band contains both myosin and actin filaments.