Final answer:
The part of the nephron that reabsorbs electrolytes, water, and glucose, excretes waste such as creatinine, urea, and ammonia, and secretes H+ to maintain blood pH is the proximal convoluted tubule (PCT). Option a is the correct answer.
Step-by-step explanation:
The nephron is the functional unit of the kidney, each composed of different sections with specific roles in the process of filtering blood, reabsorbing necessary substances, and excreting waste. The question asks which part of the nephron reabsorbs electrolytes, water, and glucose; excretes creatinine, urea, and ammonia; and secrets 90% of the H+ for blood pH maintenance.
The correct option for the described functions is: (a) Proximal convoluted tubule. The proximal convoluted tubule (PCT) is responsible for the reabsorption of ions, water, and nutrients such as glucose from the filtrate into the interstitial fluid and actively transports toxins and waste products like creatinine, urea, and ammonia into the filtrate.
It also plays a critical role in pH regulation by selectively secreting ammonia, which reacts with H+ to form NH4+ and manages the acidity of the filtrate. These functions are essential to maintain homeostatic plasma concentrations and acid-base balance in the body.