PYQ Pattern 1: GFR and Urine Output Paradox
Tested: NEET 2019, 2022. The GFR of 125 mL/min is given, and students are asked how much urine is produced per day. The trap: 125 × 60 × 24 ÷ 1000 = 180 L of FILTRATE. But 99% is reabsorbed → only ~1.5 L of actual urine. Students who answer 180 L have selected the filtrate volume, not the urine volume. Key answer: 1.5 L/day.
PYQ Pattern 2: Loop of Henle Permeability
Tested: NEET 2020, 2023. Questions ask about differential permeability of the two limbs. Trap: options always include the reversed scenario. Standard answer: descending limb = water-permeable, solute-impermeable. Ascending limb = solute-permeable (NaCl), water-impermeable. This is the most commonly confused factual pair in this chapter.
PYQ Pattern 3: Excretion Mode Classification
Tested: NEET 2018, 2021. Questions give an organism and ask its excretion mode. Key traps: (a) Tadpoles = ammonotelic, adult frogs = ureotelic. (b) Marine fish = ureotelic (not ammonotelic). (c) Insects in terrestrial context = uricotelic. (d) Sharks = ureotelic. Students often assume all aquatic = ammonotelic.
PYQ Pattern 4: RAAS Sequence
Tested: Multiple years. Assertion-reason questions on RAAS are common. The correct sequence: Low BP → JG cells → Renin → Angiotensinogen → Angiotensin I → ACE → Angiotensin II → Aldosterone → Na+ reabsorption + K+ secretion → increased blood volume and pressure.
PYQ Pattern 5: Hormone Source and Action
Tested: Every year. High-yield facts: ADH synthesized in hypothalamus, released from posterior pituitary. Aldosterone from adrenal cortex (zona glomerulosa). ANF from cardiac atrial wall cells when blood volume is HIGH. Renin from juxtaglomerular (JG) cells of afferent arteriole when BP is LOW.
PYQ Pattern 6: Disorders Identification
Tested: Every 2 years. Uremia = urea in blood (kidney failure). Glomerulonephritis = inflamed glomeruli (post-streptococcal; haematuria + proteinuria). Renal calculi = most common type is calcium oxalate. Dialysis = semipermeable membrane; dialysing fluid contains glucose and amino acids at normal plasma levels.