The kidney and urea removalEdexcel International A Level Biology: Subtopic test

1. 1
   A student prepares a longitudinal section of a mammalian kidney and a stained microscope slide of kidney tissue. She labels the main regions so that she can locate the different parts of the nephrons.

   (a)

   Which region of the kidney contains the Bowman's capsules and glomeruli?

   [1 mark]

   • AMedulla
   • BCortex
   • CRenal pelvis
   • DUreter

   (b)

   Which pair of structures is found mainly in the medulla?

   [1 mark]

   • AGlomerulus and proximal convoluted tubule
   • BBowman's capsule and distal convoluted tubule
   • CLoop of Henle and collecting duct
   • DAfferent arteriole and efferent arteriole

   (c)

   The glomerulus is a knot of capillaries. Explain how the arrangement of the arterioles supplying and draining the glomerulus helps to produce a high hydrostatic pressure in the glomerulus.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A dietitian is advising an athlete who eats a very high-protein diet. Her daily intake of amino acids is much greater than the amount she needs to make new proteins, and her urine contains a large amount of urea.

   (a)

   Which process in liver cells removes the amino group from an excess amino acid?

   [1 mark]

   • ADeamination
   • BDecarboxylation
   • CHydrolysis
   • DGlycolysis

   (b)

   Which statement about urea is correct?

   [1 mark]

   • AIt is produced in the kidneys from ammonia and then released into the blood
   • BIt is stored in liver cells until it is needed to make proteins
   • CIt is carried from the liver to the kidneys in bile
   • DIt is produced in the liver and carried to the kidneys in the blood plasma

   (c)

   Explain why the liver converts ammonia to urea before it is excreted.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A researcher analyses samples taken from a healthy adult. Blood plasma contains protein at about 70 g dm⁻³, glucose at 0.9 g dm⁻³ and urea at 0.3 g dm⁻³. Fluid collected from inside the Bowman's capsule contains no protein, glucose at 0.9 g dm⁻³ and urea at 0.3 g dm⁻³. Blood in the glomerulus has a hydrostatic pressure of 8.0 kPa, the fluid in the Bowman's capsule exerts a pressure of 2.0 kPa, and the plasma proteins exert an osmotic pressure of 3.5 kPa. Both of the last two oppose filtration.

   (a)

   Explain why the fluid in the Bowman's capsule contains glucose and urea at the same concentrations as the plasma but contains no protein.

   [3 marks]

   (b)

   Calculate the net pressure forcing fluid out of the glomerulus. Then suggest how a narrowing of the efferent arteriole would affect the volume of filtrate formed.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two patients have blood tests. Patient X has liver disease: her blood urea concentration is low and her blood ammonia concentration is raised. Patient Y has a healthy liver but has lost about 70% of his functional nephrons after an infection: his blood urea concentration is high and his urine volume is low. A biopsy of Patient Y's kidney shows that the damage is confined to the cortex.

   (a)

   Explain the blood results of Patient X and Patient Y.

   [6 marks]

   (b)

   Describe the structures found in the cortex and in the medulla of the kidney. Use this to explain why Patient Y's blood urea is high even though the structures of his medulla appear normal.

   [6 marks]

   Total for question 4: 12 marks

End of questions