The Kidneys

Question 1

If the glomerular filtrate of a diabetic person contains a high concentration of glucose, he produces a larger volume of urine. Explain why.

(3 marks)

Answer 1

. Glucose in filtrate lowers water potential;

Ignore ‘urine’. Accept increase solute potential

. Lower water potential gradient / less difference in water potential filtrate - water potential plasma;

. Less water reabsorbed by osmosis;

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. If someone has diabetes, there is a high concentration of glucose in the filtrate.
. This lowers the water potential and reduces the water potential gradient between the filtrate and blood plasma.
. This means less water is reabsorbed into blood by osmosis. (people with diabetes urinate a lot)

Question 2

Describe how ultrafiltration produces glomerular filtrate. (5 marks)

Answer 2

1. Blood pressure / hydrostatic pressure;
2. Small molecules / named example;

3 Pass through basement membrane / basement membrane acts as filter;

4. Protein too large to go through / large so stays behind;
5. Presence of pores in capillaries / presence of podocytes;