1. 1
   A doctor is explaining to a patient with reduced kidney function what the body needs to remove from the blood, and how this differs from the waste product removed by the lungs.

   (a)

   Which gas is removed from the body mainly by the lungs?

   [1 mark]

   • AUrea
   • BCarbon dioxide
   • CExcess ions
   • DGlucose

   (b)

   In addition to carbon dioxide removed by the lungs, which three substances do the kidneys normally remove from the blood?

   [1 mark]

   • AGlucose, amino acids and fats
   • BOxygen, water and glucose
   • CUrea, excess water and excess ions
   • DHaemoglobin, urea and fats

   (c)

   Explain why the kidneys, rather than the lungs, are responsible for removing urea from the blood.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student traces, without looking at any diagram, the pathway taken by urine from the organ where it is produced to the point where it leaves the body.

   (a)

   Which organ produces urine by filtering the blood?

   [1 mark]

   • ABladder
   • BKidney
   • CUreter
   • DUrethra

   (b)

   Which tube carries urine from the kidney to the bladder?

   [1 mark]

   • AUrethra
   • BVena cava
   • CUreter
   • DAorta

   (c)

   Describe the roles of the bladder and the urethra in the removal of urine from the body.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A biology class studies a description of a human kidney: an outer region packed with thousands of tiny filtering units, and an inner region where the tubes from these units drain into a central space before urine passes on towards the bladder.

   (a)

   Name the two regions of the kidney described, and outline where the process of filtration of the blood takes place.

   [3 marks]

   (b)

   Describe what happens to glucose, water and ions as fluid passes from the glomerulus, along the rest of the nephron, to form urine.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   After eating a meal very rich in protein, a person's liver processes the excess amino acids that the body does not need, before waste products of this process eventually leave the body in urine.

   (a)

   Explain, in order, what happens to the excess amino acids from the protein-rich meal, from their arrival at the liver through to a waste product leaving the body in urine.

   [6 marks]

   (b)

   Explain why it is important that the body removes urea, rather than allowing it to build up, and suggest what might happen to a person whose kidneys stopped working effectively.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   During a long-distance run in hot weather, an athlete sweats heavily, and their kidneys must still remove urea from the blood while adjusting how much water is retained.

   (a)

   Besides urea, which other substances do the kidneys remove from the blood together with the water that forms urine?

   [1 mark]

   • AExcess ions
   • BGlucose
   • COxygen
   • DHaemoglobin

   (b)

   Which organ removes most of the carbon dioxide produced by the athlete's increased rate of respiration during the run?

   [1 mark]

   • AKidneys
   • BLiver
   • CSkin
   • DLungs

   (c)

   Even though the athlete is losing a lot of water as sweat, explain why the kidneys must still remove urea from the blood rather than retaining it to conserve water.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A patient has a kidney stone, a small hard lump, blocking the tube that carries urine away from one kidney, causing urine to build up before it can reach the bladder.

   (a)

   Which structure is most likely to be blocked by the kidney stone described?

   [1 mark]

   • AUreter
   • BRenal artery
   • CNephron
   • DUrethra

   (b)

   Once urine reaches the bladder normally, which structure eventually carries it out of the body?

   [1 mark]

   • AUreter
   • BRenal vein
   • CUrethra
   • DAorta

   (c)

   Explain why a blockage in the tube described would cause urine to build up in that kidney rather than reaching the bladder.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   Scientists compare the concentration of urea and glucose in the fluid entering a nephron from the glomerulus with the concentration of urea and glucose in the urine that finally leaves the nephron.

   (a)

   Explain why glucose is present in the fluid that enters the nephron from the glomerulus, but is absent from the urine that finally leaves the nephron.

   [3 marks]

   (b)

   Explain why the concentration of urea in the urine leaving the nephron is much higher than the concentration of urea in the fluid that entered the nephron from the glomerulus.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A patient with long-term kidney failure needs regular dialysis treatment, which uses a machine to filter their blood because their own kidneys can no longer remove urea and excess substances effectively.

   (a)

   Explain what would happen inside this patient's body if the urea normally removed by healthy kidneys was allowed to build up untreated, and explain how the deamination of excess amino acids in the liver contributes to the urea that needs to be removed.

   [6 marks]

   (b)

   Explain how the process of filtration and reabsorption in a healthy nephron normally achieves what the dialysis machine must now do artificially for this patient.

   [6 marks]

   Total for question 8: 12 marks

End of questions