Most electrolyte reabsorption by the renal tubules is:

• A. an active process limited to the loop of Henle
• B. primarily regulated by the collecting duct
• C. a process that occurs in the proximal convoluted tubule
• D. mainly a passive process in the distal convoluted tubule

Answer: (C)

Verified step by step guidance

1. Understand the role of electrolytes in the body: Electrolytes are charged particles (ions) like sodium (Na+), potassium (K+), and chloride (Cl-) that are essential for maintaining fluid balance, nerve function, and muscle contraction.
2. Review the anatomy of the nephron: The nephron is the functional unit of the kidney, consisting of structures like the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Each part has specific roles in filtration, reabsorption, and secretion.
3. Focus on the proximal convoluted tubule: This is the primary site for reabsorption of electrolytes, glucose, amino acids, and water. Reabsorption here is an active process, meaning it requires energy (ATP) to transport substances against their concentration gradient.
4. Differentiate between active and passive processes: Active transport involves energy expenditure, while passive transport relies on diffusion or osmosis. Electrolyte reabsorption in the proximal convoluted tubule is active, whereas some passive processes occur in other parts of the nephron, like the distal convoluted tubule.
5. Clarify regulation by the collecting duct: The collecting duct primarily regulates water reabsorption under the influence of antidiuretic hormone (ADH) and plays a minor role in electrolyte handling compared to the proximal convoluted tubule.