_________muscle fibres store much oxygen in combination with __________________.

Answer

**Step-by-Step Solution:**

1. **Identify the Type of Muscle Fibers**: The question asks about muscle fibers that store oxygen. The two main types of muscle fibers are red muscle fibers and white muscle fibers.

2. **Focus on Red Muscle Fibers**: Red muscle fibers, also known as slow-twitch fibers, are the ones that store more oxygen. They appear red due to the presence of a specific pigment.

3. **Identify the Pigment**: The pigment responsible for storing oxygen in red muscle fibers is called myoglobin.

4. **Explain the Function of Myoglobin**: Myoglobin binds to oxygen in the muscle fibers, forming a compound called oxymyoglobin. This compound is crucial for oxygen storage.

5. **Describe the Role of Oxymyoglobin**: During muscle contraction, oxymyoglobin releases the stored oxygen, which is essential for sustaining muscle activity and preventing fatigue.

6. **Conclude the Answer**: Therefore, the complete answer to the question is: "Red muscle fibers store much oxygen in combination with myoglobin."

**Final Answer**: Red muscle fibers store much oxygen in combination with myoglobin.

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