Skeletal muscles fibre has light and dark bands. Which is correct match of protein with its light refractive property and colour

Options

A. `{:(,"Protein","Colour","Property",),((A),"Myosin","Light","Anisotropic",):}`
B. `{:(,"Protein","Colour","Property",),((B),"Actin","Dark","Anisotropic",):}`
C. `{:(,"Protein","Colour","Property",),((C ),"Myosin","Dark","Isotropic",):}`
D. `{:(,"Protein","Colour","Property",),((D),"Actin","Light","Isotropic".,):}`

Answer

To solve the question regarding the skeletal muscle fiber's light and dark bands and the correct match of protein with its light refractive property and color, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Muscle Fibers**: Skeletal muscle fibers are composed of two main types of proteins: actin and myosin. These proteins are responsible for the striated appearance of skeletal muscles, which consists of alternating light and dark bands.

2. **Identifying the Bands**:
- The **light bands** are known as **I bands**, which primarily consist of **actin** filaments.
- The **dark bands** are known as **A bands**, which primarily consist of **myosin** filaments.

3. **Properties of Actin and Myosin**:
- **Actin**: This is a thin filament that appears light under a microscope. It is associated with regulatory proteins such as tropomyosin and troponin.
- **Myosin**: This is a thick filament that appears dark under a microscope. It is responsible for forming cross-bridges during muscle contraction.

4. **Refractive Properties**:
- The **I bands** (light bands) are **isotropic**, meaning they do not change the direction of polarized light passing through them.
- The **A bands** (dark bands) are **anisotropic**, meaning they do change the direction of polarized light.

5. **Analyzing the Options**:
- **Option A**: Myosin is light - Incorrect (Myosin is dark).
- **Option B**: Actin is dark - Incorrect (Actin is light).
- **Option C**: Myosin is dark but isotropic - Incorrect (Myosin is dark but anisotropic).
- **Option D**: Actin is light and isotropic - Correct (Actin is light and isotropic).

6. **Conclusion**: The correct match of protein with its light refractive property and color is **Option D**: Actin is light and isotropic.