Which of the following is not feature of red muscle fibres ?

Options

A. (1) They have plenty of mitochondria
B. (2) They have high content of myoglobin
C. (3) They have high amount of sarcoplasmic reticulum
D. (4) They are called aerobic muscles

Answer

To determine which of the following is not a feature of red muscle fibers, we will analyze each option provided:

1. **They have plenty of fibers**: Red muscle fibers, also known as slow-twitch fibers, are characterized by their endurance and ability to sustain prolonged activity. They are indeed composed of numerous fibers that are capable of efficient oxygen use.

2. **They have high content of myoglobin**: Red muscle fibers contain a high concentration of myoglobin, which is a red pigment that stores oxygen. This feature is crucial for their function in aerobic respiration, allowing them to produce energy efficiently during extended periods of activity.

3. **They have high amount of sarcoplasmic reticulum**: The sarcoplasmic reticulum is responsible for storing calcium ions and plays a significant role in muscle contraction. However, red muscle fibers do not have a high amount of sarcoplasmic reticulum compared to white muscle fibers. This is a distinguishing feature, as red muscle fibers rely more on aerobic metabolism rather than rapid contractions that require extensive calcium storage.

4. **They are called aerobic muscles**: Red muscle fibers are indeed referred to as aerobic muscles because they primarily use oxygen for energy production through aerobic respiration.

Based on the analysis of the options, the statement that is **not a feature of red muscle fibers** is:

**Correct Answer: They have high amount of sarcoplasmic reticulum.**