Which of the following contractile proteins contributes 55% of muscle protein by weight?

Options

A. Tropomyosin
B. Troponin
C. Myosin
D. Actin

Explanation

To answer the question regarding which contractile protein contributes 55% of muscle protein by weight, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Muscle Composition**:
- Skeletal muscles are composed of various proteins, primarily contractile proteins that facilitate muscle contraction.

2. **Identifying the Main Contractile Proteins**:
- The two primary contractile proteins in skeletal muscles are **actin** and **myosin**.
- Actin is associated with the light bands (thin filaments), while myosin is associated with the dark bands (thick filaments).

3. **Analyzing the Contribution of Each Protein**:
- Myosin is known to be the predominant protein in muscle tissue. It is responsible for the majority of muscle contraction.
- In terms of weight contribution, myosin accounts for approximately **55%** of the total muscle protein.

4. **Conclusion**:
- Based on the information gathered, the contractile protein that contributes 55% of muscle protein by weight is **myosin**.

### Final Answer:
The contractile protein that contributes 55% of muscle protein by weight is **myosin**.

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