NEET BIOLOGY

Detailed explanation-1: -According to our results urea diffuses very rapidly from RBC to plasma and is almost at equilibrium at the dialyser outlet; thus the extraction of urea during dialysis is from both plasma and RBC.

Detailed explanation-2: -Vasopressin, upon binding to V2 receptors in the inner medullary collecting ducts, increases urea permeability through activation of UT-A1 molecules, thus enabling urea to diffuse into the inner medullary interstitium.

Detailed explanation-3: -Urea apparently permeates the red cell membrane via a facilitated diffusion system, which plays an important role when red blood cells traverse the renal medulla; rapid urea transport helps preserve the osmotic stability and deformability of the cell, and it helps prevent dissipation of extracellular osmotic gradients.

Detailed explanation-4: -Where does urea enter the blood? The urea enters the blood via the liver. Nearly 80 percent of the nitrogen expelled by humans and other mammals takes the form of urea, which is made in the mitochondrial matrix and cytosol of liver cells.

Detailed explanation-5: -1976; Kato & Sands, 1998), it is generally considered that urea is passively transported across biological membranes by diffusion. In recent years, specific transporters for urea have been identified in the renal medulla and cloned (for a review see Tsukaguchi et al. 1998).