For conversion of prothrombin into thrombin, which of the following is required

Options

A. Fibrinogen
B. Vitamin K.
C. Proconvertin
D. Thrombokinase

Answer

To determine what is required for the conversion of prothrombin into thrombin, we can analyze the options provided:

1. **Understanding Prothrombin and Thrombin**:
- Prothrombin is a plasma protein that is converted into thrombin, an enzyme that plays a crucial role in blood coagulation.

2. **Identifying the Conversion Process**:
- The conversion of prothrombin to thrombin is a key step in the coagulation cascade, which is essential for blood clotting.

3. **Evaluating the Options**:
- **Fibrinogen**: This is not directly involved in the conversion of prothrombin to thrombin. Instead, fibrinogen is converted into fibrin by thrombin.
- **Vitamin K**: While vitamin K is essential for the synthesis of prothrombin, it does not directly convert prothrombin into thrombin.
- **Proconvertin**: This is another name for factor VII, which is involved in the coagulation cascade but does not directly convert prothrombin into thrombin.
- **Thrombokinase**: This is the correct answer. Thrombokinase, also known as thromboplastin, is a mixture of phospholipids and tissue factors that catalyzes the conversion of prothrombin into thrombin.

4. **Conclusion**:
- The correct answer is **Thrombokinase**.

### Step-by-Step Solution:
1. Identify the proteins involved in blood coagulation (prothrombin and thrombin).
2. Understand the role of thrombokinase in the conversion process.
3. Evaluate each option provided to determine which is directly responsible for the conversion of prothrombin to thrombin.
4. Conclude that thrombokinase is required for this conversion.