BioMedical Admissions Test (BMAT) 2025 – 400 Free Practice Questions to Pass the Exam

Selective reabsorption in the kidneys primarily relies on active transport mechanisms. This process is essential for the kidneys to reclaim valuable substances from the filtrate back into the bloodstream. Active transport involves the movement of ions and molecules against their concentration gradient, which requires energy, usually in the form of ATP.

In the context of renal function, substances such as glucose, amino acids, and various ions (like sodium and potassium) are actively reabsorbed in different segments of the nephron. For example, in the proximal convoluted tubule, glucose and sodium ions are actively transported back into the blood, allowing the body to maintain homeostasis and conserve resources.

Other mechanisms like diffusion and facilitated diffusion do play roles in kidney function, but they do not account for the specificity and energy requirements of selective reabsorption. Diffusion relies on concentration gradients, while facilitated diffusion uses carrier proteins to help move substances but still does not require energy. Therefore, the requirement of energy and specificity in the reabsorption of key substances underscores why active transport is the correct mechanism involved in selective reabsorption in the kidneys.