Which of the following is not a part of the filtration membrane?

Correct Answer: C

Rationale: Capsular space isn't part of the filtration membrane it's the filtrate receptacle (Bowman's space). Fenestrated endothelium, visceral membrane (podocytes), and filtration slits (with basement membrane) form the barrier plasma filters through. Space as destination distinguishes it, critical for filtration anatomy, unlike structural components.

Correct Answer: A

Rationale: The proximal tubule is the primary site for organic ion secretion e.g., urate, creatinine via transporters (e.g., OATs). Loop of Henle concentrates minimal secretion. Distal tubule secretes H /K less organic. Collecting duct adjusts not primary. Proximal dominance distinguishes it, key to waste excretion, unlike later segments.

Correct Answer: B

Rationale: Proximal tubule reabsorption is isosmotic water follows Na (e.g., ~65% reclaimed), maintaining osmolarity. Leaky epithelium is permeable false. Na uses transcellular/paracellular not only transcellular. Chloride rises in lumen drives later reabsorption. Isosmotic nature distinguishes it, key to bulk reabsorption, unlike permeability or ion errors.

Correct Answer: B

Rationale: PCT fluid is isosmotic water follows Na reabsorption (e.g., ~65% reclaimed), matching plasma. Hyperosmotic requires concentration later nephron. Hypoosmotic needs dilution ascending limb. ADH affects distal not PCT. Isosmotic balance distinguishes it, key to proximal bulk flow, unlike osmotic shifts.

Correct Answer: B

Rationale: Most enzymes function optimally at pH 7.4 physiological blood pH (e.g., neutral catalysis). 7.8 is alkalotic disrupts activity. 6.8 is acidic suboptimal. 2 is gastric extreme. Physiological pH distinguishes it, key to enzyme kinetics, unlike alkaline, acidic, or gastric values.