Edexcel IGCSEBiologyGeneral Applications8 Marks

The kidneys play a vital role in osmoregulation and excretion.

(a)Name a waste product, other than water, that is removed from the blood by the kidneys.[1]
(b)Describe the process of ultrafiltration in the kidney.[4]
(c)Explain why the presence of glucose in the urine can be a symptom of diabetes.[3]

Mark scheme

Marking points from the official mark scheme. The mark or mark type is shown in brackets.

18(a) B1: urea / mineral salts / excess vitamins (1)
18(b) M1: blood enters glomerulus under high pressure (1)
M1: small molecules (water, urea, salts, glucose, amino acids) are forced out (1)
M1: through the pores in the Bowman's capsule (1)
A1: (large molecules like) proteins / blood cells are too large to pass through (1)
18(c) M1: in diabetes, blood glucose levels are too high (1)
M1: (due to insufficient insulin / cells not responding to insulin) (1)
A1: not all glucose can be reabsorbed (in the kidney tubules) (1)
M1: (as) carrier proteins for glucose reabsorption are saturated / limited (1)

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