Final answer:
The Proximal Convoluted Tubule (PCT) is the most metabolically active part of a nephron, heavily involved in reclaiming solutes and water to maintain homeostasis.
Step-by-step explanation:
The most metabolically active part of a nephron is the Proximal Convoluted Tubule (PCT). The PCT is responsible for the reabsorption and secretion of various substances such as glucose, amino acids, bicarbonate, electrolytes, and water. It utilizes energy-intensive processes like active transport, powered by ATP, which is generated by the high concentration of mitochondria in its cells. Mechanisms such as symporters, antiporters, and ATPase active transporters operate alongside simple and facilitated diffusion to reclaim nearly 100% of certain solutes and create an osmotic gradient for water recovery. This high metabolic activity ensures the maintenance of homeostasis within the body.