Trap 1: Frog Excretion Mode
Wrong: Frogs are always ammonotelic. Right: Tadpoles (aquatic phase) = ammonotelic. Adult frogs (terrestrial phase) = ureotelic. Metamorphosis triggers the switch.
Trap 2: Marine Fish Excretion Mode
Wrong: All aquatic animals are ammonotelic. Right: Marine bony fish are UREOTELIC (not ammonotelic). They live in hyperosmotic seawater and lose water by osmosis, so they cannot afford extra water loss for ammonia excretion. Sharks/elasmobranchs also ureotelic.
Trap 3: GFR vs Urine Volume
Wrong: GFR of 125 mL/min means 125 L/day of urine is produced. Right: GFR produces 180 L/day of filtrate, but 99% is reabsorbed → only ~1.5 L of urine per day. Never confuse filtrate volume with urine volume.
Trap 4: Loop of Henle Permeability (Mixed Up)
Wrong: Descending limb pumps out NaCl; ascending limb lets water out. Right: Descending limb = water-permeable, solute-impermeable. Ascending limb = solute-permeable (NaCl pumped out), water-impermeable. Mnemonic: D = Drinks water. A = Allows salts out.
Trap 5: ADH Source
Wrong: ADH is produced in the posterior pituitary. Right: ADH is SYNTHESIZED in the hypothalamus and STORED and RELEASED from the posterior pituitary. The distinction between synthesis and release site is NEET-tested.
Trap 6: Aldosterone Source vs ADH Source
Wrong: Both ADH and aldosterone come from the same gland. Right: ADH = posterior pituitary (synthesized in hypothalamus). Aldosterone = adrenal CORTEX (zona glomerulosa). Completely different glands.
Trap 7: ANF Trigger
Wrong: ANF is released when blood volume is LOW (same trigger as RAAS). Right: ANF is released when blood volume is HIGH (atrial stretching). RAAS is activated when blood volume/pressure is LOW. They have opposite triggers and opposite effects.
Trap 8: Ornithine Cycle Location
Wrong: The kidney converts ammonia to urea. Right: The LIVER (not kidney) converts ammonia to urea via the ornithine cycle. The kidney only filters and excretes the urea that arrives from the liver.
Trap 9: Dialysis Fluid Composition
Wrong: Dialysing fluid contains no glucose or amino acids (to maximise removal of all substances from blood). Right: Dialysing fluid DOES contain glucose and amino acids at NORMAL PLASMA LEVELS to prevent their loss from blood. Only waste products (urea, excess ions) have a gradient to diffuse out.
Trap 10: Cortical vs Juxtamedullary Nephrons for Concentration
Wrong: All nephrons equally contribute to concentrated urine. Right: Only juxtamedullary nephrons (15%, with long loops of Henle) are responsible for producing concentrated urine. Cortical nephrons (85%, with short loops) play minimal role in concentration.