During muscle contraction , hydrolysis of ATP results in a change in the .

Options

A. structure of the myofibrils
B. conformation of myosin
C. conformation of actin
D. structure of the sarcoplasmic reticulum

Answer

### Step-by-Step Solution:

1. **Understanding Muscle Contraction**: Muscle contraction involves the interaction between two types of proteins: actin (thin filaments) and myosin (thick filaments). The process is primarily explained by the sliding filament theory, where these filaments slide over each other to shorten the muscle.

2. **Role of ATP in Muscle Contraction**: ATP (adenosine triphosphate) is crucial for muscle contraction. When ATP is hydrolyzed, it releases energy that is used for the contraction process.

3. **Myosin's Structure and Function**: Myosin is composed of monomers called meromyosin, which have a globular head that protrudes. This globular head acts as an ATPase enzyme, meaning it can hydrolyze ATP to release energy.

4. **Cross-Bridge Formation**: The globular head of myosin binds to actin to form a cross-bridge. This binding is essential for muscle contraction, as it allows the myosin heads to pull the actin filaments towards the center of the sarcomere.

5. **Conformational Change**: The hydrolysis of ATP causes a conformational change in the myosin head. This change is what allows the myosin to pull on the actin filaments, leading to muscle contraction.

6. **Conclusion**: Therefore, during muscle contraction, the hydrolysis of ATP results in a change in the conformation of the myosin protein, specifically in its globular head that interacts with actin.

### Final Answer:
The hydrolysis of ATP during muscle contraction results in a change in the **conformation of the myosin protein**.

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