Dialysis Fluid Composition — NEET Biology

Correct answer: A — A–ii, B–i, C–iii, D–i

The core concept is the selective permeability of the cellophane membrane in hemodialysis and the composition of the dialysing fluid. (A) Urea: "As nitrogenous wastes are absent in the dialysing fluid, these substances freely move out, thereby clearing the blood." So, urea diffuses from blood into the dialysing fluid. This matches (ii). (B) Plasma proteins: "Blood is filtered so finely through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule." While this describes glomerular filtration, the principle holds for the cellophane membrane; large plasma proteins do not pass. Thus, plasma proteins remain in the blood. This matches (i). (C) Glucose: "Dialysing fluid... having the same composition as that of plasma except the nitrogenous wastes." This implies that essential substances like glucose are present in the dialysing fluid at a concentration similar to blood plasma to prevent their loss from the patient's blood. This matches (iii). (D) Red blood cells: Red blood cells are too large to pass through the cellophane membrane, similar to plasma proteins. They remain in the blood. This matches (i). Therefore, the correct match is A–ii, B–i, C–iii, D–i.