Glomerular hydrostatic pressure (GHP):

Correct Answer: A

Rationale: Glomerular hydrostatic pressure (~55 mmHg) pushes fluid out drives filtration (e.g., Starling force). Back into vessels is oncotic/capsular opposes. No effect ignores its role false. Varying with oncotic misaligns independent. Outward push distinguishes it, critical for GFR, unlike opposing or neutral errors.

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.

Correct Answer: C

Rationale: Respiratory isn't a chemical buffer physiological via COâ‚‚ excretion (e.g., lungs). Phosphate, bicarbonate, and proteins are chemical bind H directly. Respiratory's physiological role distinguishes it, key to system classification, unlike chemical buffers.