A technician uses dialysis tubing to model a stage of dialysis treatment. Fig. 1 shows the tubing filled with blood-like solution and immersed in fresh dial...

Assessment: Human Biology 4HB1 | Paper 1 Mock 01 | Written Paper 1 Subject: Human Biology - 4HB1

Question 1 Report

A technician uses dialysis tubing to model a stage of dialysis treatment. Fig. 1 shows the tubing filled with blood-like solution and immersed in fresh dialysis solution. The membrane allows small molecules through but not blood cells or proteins.

dialysis solutiontubingblood-likesolution© EAGLE BEACON GLOBAL

(a) State the name of the process by which urea moves out of the tubing. [1]
(b) Explain why the dialysis solution must contain no urea at the start of treatment. [2]
(c) Name one large component of blood that should stay inside the tubing. [1]

Answer Details

(a) Urea moves out of the tubing by diffusion. [1 mark]

(b) At the start, dialysis solution must contain no urea so that urea concentration is higher in the blood-like solution than in the dialysis solution. Urea can then diffuse out down its concentration gradient. [2 marks]

(c) One large component that should remain inside is a red blood cell. White blood cells, platelets, or proteins are also acceptable. [1 mark]

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