What role does thromboplastin play?

Explanation

**Step-by-Step Solution:**

1. **Definition of Thromboplastin**: Thromboplastin, also known as thrombokinase, is a plasma protein that plays a crucial role in the blood coagulation process.

2. **Function in Blood Coagulation**: The primary role of thromboplastin is to aid in blood coagulation, which is the process that prevents excessive bleeding when a blood vessel is injured.

3. **Catalytic Action**: Thromboplastin catalyzes the conversion of prothrombin, a plasma protein, into thrombin. This is a key step in the coagulation cascade.

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