Urea reabsorption is

Options

A. Active process
B. Passive process
C. Active at CD
D. Active at PCT

Answer

### Step-by-Step Solution for the Question: Urea Reabsorption

1. **Understanding Urea Reabsorption**:
- Urea is a waste product formed from the breakdown of proteins. It is primarily excreted from the body through urine. However, before it is excreted, the body reabsorbs some of it for various physiological reasons.

2. **Role of Nephron**:
- The nephron is the functional unit of the kidney responsible for filtering blood and forming urine. It consists of several parts, each playing a role in the processes of filtration, reabsorption, and secretion.

3. **Sites of Reabsorption**:
- The primary site for urea reabsorption is the **Proximal Convoluted Tubule (PCT)**. This is where approximately 50% of the filtered urea is reabsorbed.
- Other sites include the **Loop of Henle** and the **Collecting Duct**, but the amount reabsorbed in these areas is significantly less compared to the PCT.

4. **Mechanism of Reabsorption**:
- Urea reabsorption occurs mainly through **passive transport**. This means that it does not require energy (ATP) for the process. Instead, urea moves along its concentration gradient.
- In contrast, other substances like sodium and amino acids are reabsorbed through **active transport**, which does require energy.

5. **Conclusion**:
- Therefore, the process of urea reabsorption is primarily passive and occurs predominantly in the Proximal Convoluted Tubule (PCT).

### Final Answer:
Urea reabsorption is a passive process that occurs mainly in the Proximal Convoluted Tubule (PCT) of the nephron, where approximately 50% of the filtered urea is reabsorbed.

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