AP BIOLOGY

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ANIMAL PHYSIOLOGY

EXCRETION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
In order to aid water reabsorption, excessive salt is pumped out from the filtrate at the ____
A
glomerulus
B
Bowman’s capsule
C
First coiled tubule
D
Loop of Henle
Explanation: 

Detailed explanation-1: -Water present in the filtrate in the papillary duct flows through aquaporin channels out of the duct, moving passively down its concentration gradient. This process reabsorbs water and creates a concentrated urine for excretion.

Detailed explanation-2: -The primary function of the loops of Henle and the thick ascending limb of the distal tubule is the concentration of urine utilizing a principle called ‘countercurrent multiplication.

Detailed explanation-3: -Reabsorption of Na+ in the thick ascending limb of Henle’s loop (TAL) occurs through (1) transcellular pathways involving the Na+-2Cl−-K+ cotransporter in the apical membrane and (2) paracellular pathways driven by the lumen positive transepithelial potential difference.

Detailed explanation-4: -(3) They reabsorb large amounts of potassium, calcium, and magnesium in an energy-efficient manner.

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