Red muscle fibres are rich in

Options

A. cholesterol
B. lysosomers
C. microsomes
D. mitochondria

Answer

**Step-by-Step Solution:**

1. **Identify the Types of Muscle Fibers**: There are two main types of muscle fibers: red muscle fibers and white muscle fibers.

2. **Understand the Characteristics of Red Muscle Fibers**: Red muscle fibers are characterized by their red color, which is primarily due to the presence of myoglobin.

3. **Explain Myoglobin's Role**: Myoglobin is a protein that binds oxygen, similar to hemoglobin in blood. However, myoglobin can only carry one oxygen molecule at a time, which contributes to the red color of these muscle fibers.

4. **Discuss Mitochondria in Red Muscle Fibers**: Red muscle fibers are also rich in mitochondria, which are the powerhouses of the cell. This abundance of mitochondria allows red muscle fibers to perform aerobic respiration efficiently.

5. **Contrast with White Muscle Fibers**: In contrast, white muscle fibers have less myoglobin and fewer mitochondria, which makes them more suited for anaerobic respiration.

6. **Application in Physical Activity**: Fast runners, who require a high supply of energy and oxygen, have a higher proportion of red muscle fibers in their legs. In contrast, long-distance runners may have more white muscle fibers.

7. **Conclusion**: The question asks what red muscle fibers are rich in, and based on the discussion, the correct answer is that they are rich in myoglobin and mitochondria.

**Final Answer**: Red muscle fibers are rich in myoglobin and mitochondria.

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