Conversion of fibrinogen to fibrin is catalysed by

Options

A. thrombin
B. prothrombin
C. thromboplastin
D. all of these

Explanation

To answer the question regarding the conversion of fibrinogen to fibrin, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Fibrinogen and Fibrin**:
- Fibrinogen is a soluble plasma protein produced by the liver.
- Fibrin is the insoluble form of fibrinogen that plays a crucial role in blood clotting.

2. **Role of Thrombin**:
- The conversion of fibrinogen to fibrin is specifically catalyzed by the enzyme thrombin.
- Thrombin is an enzyme that acts on fibrinogen to convert it into fibrin.

3. **Process of Blood Clotting**:
- When a blood vessel is injured, a series of reactions occur in the body known as the coagulation cascade.
- Thrombin is generated from prothrombin (another plasma protein) during this cascade.
- Once thrombin is activated, it cleaves fibrinogen into fibrin, which then forms a mesh-like structure that helps in the formation of a blood clot.

4. **Conclusion**:
- Therefore, the enzyme responsible for the conversion of fibrinogen to fibrin is **thrombin**.

### Final Answer:
The conversion of fibrinogen to fibrin is catalyzed by **thrombin**.

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