Which of the following precipitates `Ca^(2+)` ions and consequently prevents coagulation?

Options

A. Heparin
B. Thrombin
C. Potassium oxalate/Sodium citrate
D. Antithrombin

Answer

To answer the question "Which of the following precipitates `Ca^(2+)` ions and consequently prevents coagulation?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Coagulation**: Coagulation is the process by which blood changes from a liquid to a gel, forming a blood clot. This process involves the conversion of fibrinogen (a soluble protein) into fibrin (an insoluble protein) with the help of the enzyme thrombin.

2. **Role of Calcium Ions**: Calcium ions (`Ca^(2+)`) play a crucial role in the coagulation process. They are necessary for the activation of thrombin, which is essential for converting fibrinogen to fibrin.

3. **Identifying Precipitants**: The question asks for substances that can precipitate calcium ions, thereby preventing coagulation. Precipitation means that the calcium ions will form an insoluble compound and will not be available to activate thrombin.

4. **Analyzing the Options**:
- **Thrombin**: This is an enzyme that facilitates coagulation, so it does not precipitate calcium ions.
- **Potassium Oxalate**: This compound can bind with calcium ions to form calcium oxalate, thus precipitating them and preventing coagulation.
- **Sodium Citrate**: This salt also binds with calcium ions, forming a complex that prevents them from participating in the coagulation process.
- **Antithrombin**: This is a protein that inhibits thrombin but does not directly precipitate calcium ions.

5. **Conclusion**: The two substances that can precipitate calcium ions and prevent coagulation are **Potassium Oxalate** and **Sodium Citrate**. However, since the question asks for which of the following does this, the most commonly recognized agents for this purpose are **Sodium Citrate**.

### Final Answer:
**Sodium Citrate** is the correct answer as it precipitates `Ca^(2+)` ions and consequently prevents coagulation.

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