What sacromere?

Options

A. Part between two H-line
B. Part between two A-line
C. Part between two I-band
D. Part between two Z- line

Answer

**Step-by-Step Solution:**

1. **Definition of Sarcomere**: A sarcomere is defined as the functional unit of muscle fibers. It is the smallest contractile unit within a muscle.

**Hint**: Remember that the sarcomere is crucial for muscle function.

2. **Structure of Sarcomere**: The sarcomere is composed of two main types of contractile proteins: actin and myosin. These proteins are responsible for muscle contraction.

**Hint**: Think of actin as the thin filament and myosin as the thick filament.

3. **Appearance of Proteins**: Actin appears as a light band (thin filament), while myosin appears as a dark band (thick filament) when viewed under a microscope.

**Hint**: Visualize the sarcomere's bands to remember their thickness and color differences.

4. **Z Lines**: The sarcomere is defined by the area between two Z lines. The Z lines mark the boundaries of each sarcomere.

**Hint**: Z lines are like the borders of a room, enclosing the functional unit.

5. **A Bands and I Bands**: Within the sarcomere, there are A bands (where myosin is present) and I bands (where actin is present). The A band is the darker region, while the I band is lighter.

**Hint**: A bands contain thick filaments, while I bands are only thin filaments.

6. **H Zone**: The H zone is a part of the A band where only myosin is present, and no actin overlaps. It is located in the center of the A band.

**Hint**: The H zone is like a quiet area in a busy room where only one type of filament is found.

7. **Function of Sarcomere**: The primary function of the sarcomere is to facilitate muscle contraction through the sliding filament mechanism, where actin and myosin filaments slide past each other.

**Hint**: Think of the sliding action as a way muscles shorten and generate force.

**Summary**: A sarcomere is the functional unit of muscle fibers, composed of actin and myosin filaments, defined by Z lines, and responsible for muscle contraction.

---