Where does most nutrient reabsorption occur in the nephron?

• A. Collecting duct
• B. Loop of Henle
• C. Proximal convoluted tubule
• D. Distal convoluted tubule

Answer: (C)

Verified step by step guidance

1. Begin by understanding the structure of the nephron, which is the functional unit of the kidney. The nephron consists of several parts: the glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.
2. Recognize that the proximal convoluted tubule (PCT) is the first segment of the nephron tubule after the glomerulus. It plays a crucial role in reabsorbing nutrients, ions, and water from the filtrate back into the bloodstream.
3. Identify the types of substances reabsorbed in the proximal convoluted tubule. These include glucose, amino acids, sodium ions, chloride ions, and water. The PCT is responsible for reabsorbing approximately 65-70% of the sodium and water, and nearly all glucose and amino acids.
4. Understand the mechanisms of reabsorption in the proximal convoluted tubule. This involves active transport, facilitated diffusion, and osmosis. Sodium ions are actively transported out of the tubule cells, creating an osmotic gradient that drives water reabsorption.
5. Compare the proximal convoluted tubule with other parts of the nephron. While the loop of Henle, distal convoluted tubule, and collecting duct also participate in reabsorption, the PCT is the primary site for nutrient reabsorption due to its extensive surface area and the presence of microvilli that increase absorption efficiency.