Which of the following is more in white fibres

Options

A. Myoglobin
B. Sarcosomes
C. Sarcoplasmic reticulum
D. Both 2 and 3

Answer

To solve the question "Which of the following is more in white fibers?", we will analyze each of the provided options step by step.

### Step 1: Understand White Fibers
White fibers, also known as fast-twitch fibers, are muscle fibers that are adapted for rapid and powerful contractions but fatigue quickly. They have different characteristics compared to red fibers, which are slow-twitch and more endurance-oriented.

### Step 2: Evaluate the Options
We have four options to consider. Let’s evaluate each one.

#### Option 1: Myoglobin
- Myoglobin is a protein that stores oxygen in muscle cells. It is found in higher concentrations in red muscle fibers, which require more oxygen for sustained activity. Therefore, myoglobin is **not** more prevalent in white fibers.

#### Option 2: Sarcosomes
- Sarcosomes are large mitochondria found in muscle cells. They are responsible for energy production through aerobic respiration. Red muscle fibers have a higher density of mitochondria (sarcosomes) due to their reliance on aerobic metabolism. Hence, sarcosomes are also **not** more in white fibers.

#### Option 3: Sarcoplasmic Reticulum
- The sarcoplasmic reticulum is a specialized endoplasmic reticulum in muscle cells that stores calcium ions, which are crucial for muscle contraction. White fibers have a more developed sarcoplasmic reticulum to facilitate rapid contractions. Therefore, this option is **correct**.

#### Option 4: Both 2nd and 3rd
- Since we have established that sarcosomes are not more prevalent in white fibers, this option is also **incorrect**.

### Conclusion
Based on the analysis, the correct answer is **Option 3: Sarcoplasmic Reticulum**.