The striated appearance of the myofibril is due to the distribution pattern of :

Options

A. Actin
B. Myosin
C. Calmodulin
D. Both (a) and (b)

Answer

To answer the question regarding the striated appearance of myofibrils, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Myofibrils**: Myofibrils are the basic rod-like units of a muscle cell (muscle fiber). They are responsible for muscle contraction and are composed of long, thin structures.

2. **Composition of Myofibrils**: Myofibrils are primarily made up of two types of protein filaments: thick filaments and thin filaments. The thick filaments are made of myosin, while the thin filaments are made of actin.

3. **Striated Appearance**: The striated appearance of myofibrils is due to the alternating arrangement of these thick (myosin) and thin (actin) filaments. This arrangement creates distinct dark and light bands when viewed under a microscope.

4. **Dark and Light Bands**: The regions where thick filaments (myosin) are present appear darker, while the regions with thin filaments (actin) appear lighter. This pattern of alternating bands is what gives striated muscles their characteristic appearance.

5. **Conclusion**: Therefore, the striated appearance of myofibrils is due to the distribution pattern of both actin and myosin filaments.

### Final Answer:
The striated appearance of the myofibril is due to the distribution pattern of **A and B both (Actin and Myosin)**.

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