Question

The part of nephron involved in active reabsorption of sodium is

• A. distal convoluted tubule
• B. Proximal convoluted tubule
• C. Bowman’s capsule
• D. descending limb of Henle’s loop

Answer 1

The Correct Option is B

The nephron is the functional unit of the kidney, and it is responsible for the filtration and purification of blood. Understanding the parts of the nephron and their functions is crucial in biology, particularly in topics related to human physiology and excretion systems. Let us solve the given question step-by-step.

The question asks us to identify which part of the nephron is involved in the active reabsorption of sodium.

1. Understanding the Options:
   • Distal convoluted tubule: This part of the nephron plays a role in the selective reabsorption and secretion to help maintain blood pH and electrolyte balance, but it is not predominantly responsible for the initial active reabsorption of sodium.
   • Proximal convoluted tubule (PCT): This is the first part of the nephron where a significant amount of reabsorption occurs, including the active reabsorption of sodium ions.
   • Bowman’s capsule: This is the initial part of the nephron where blood filtration occurs. It does not play a direct role in the reabsorption of sodium.
   • Descending limb of Henle’s loop: This section is mainly involved in the reabsorption of water and does not significantly reabsorb sodium.
2. Active Reabsorption of Sodium: The active reabsorption of sodium involves moving sodium ions from the tubular fluid into the blood against their concentration gradient. This process requires energy (ATP).
3. Correct Answer: Proximal convoluted tubule is involved in the active reabsorption of sodium. Approximately 65-70% of sodium in the filtrate is actively reabsorbed in the proximal convoluted tubule.
4. Explanation: In the proximal convoluted tubule, sodium is reabsorbed actively through sodium-potassium pumps located in the epithelial cells lining this tubule. This process is essential for conserving sodium, an important electrolyte, in the body.
5. Conclusion: Understanding the roles of different parts of the nephron in the process of urine formation helps in identifying the correct option. The proximal convoluted tubule is rich in mitochondria providing the energy required for active transport of ions, making it the site of active reabsorption of sodium.