1. 1
   A group of athletes are training in a hot indoor gym. During the session, scientists observe that the athletes' skin becomes flushed (red) and they produce a large volume of sweat. After training, one athlete drinks very little water during her recovery period.

   (a)

   Which organ removes excess water from the body by producing urine?

   [1 mark]

   • Athe skin
   • Bthe lungs
   • Cthe kidneys
   • Dthe liver

   (b)

   After recovering with very little water intake, the athlete produces a small volume of dark, concentrated urine. Which of these best explains this?

   [1 mark]

   • AHer pituitary gland released more ADH, causing her kidneys to reabsorb more water
   • BHer pituitary gland released less ADH, causing her kidneys to reabsorb more water
   • CHer kidneys reabsorbed less water, producing a larger volume of dilute urine
   • DHer sweat glands stopped producing sweat, so no water needed to be conserved

   (c)

   State two ways, other than in urine, that the body loses water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A 52-year-old patient with long-term liver damage has a blood test. The results show a much higher than normal concentration of ammonia in the blood, together with a lower than normal concentration of urea. The patient's doctor explains that poisonous substances that a healthy liver would normally break down are also present at raised levels in the patient's blood.

   (a)

   In a healthy liver, excess amino acids are deaminated to form ammonia, which the liver then converts into which substance for excretion?

   [1 mark]

   • Aglucose
   • Burea
   • Cglycogen
   • Dbile

   (b)

   What does the patient's raised blood ammonia and lowered urea most likely suggest?

   [1 mark]

   • AThe patient's kidneys have stopped filtering the blood
   • BThe patient is producing too much bile
   • CThe patient's liver has stopped storing iron from old blood cells
   • DThe patient's liver is no longer converting ammonia into urea effectively

   (c)

   Using the information given, explain why the raised level of poisonous substances in the patient's blood is linked to the liver damage.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A scientist measures the volume and concentration of urine produced by a healthy volunteer over one day. In the morning, after the volunteer has not drunk anything overnight, they produce 150 cm3 of urine that is dark yellow and concentrated. After lunch, the volunteer drinks 1.5 litres of water over two hours. Two hours after drinking, they produce 400 cm3 of urine that is pale and dilute.

   (a)

   Explain, in terms of ADH and the kidneys, why the volunteer's urine changed from a small volume of concentrated urine in the morning to a larger volume of dilute urine after drinking water.

   [3 marks]

   (b)

   The volunteer's kidneys filter a very large volume of blood plasma each day, but produce a much smaller volume of urine. State what happens to the glucose, dissolved ions and water that are filtered out of the blood by the kidneys, and use this to explain why so little of the filtered fluid is released as urine.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two patients, X and Y, are being monitored in hospital. Patient X has not been able to drink any fluids for several hours and feels very thirsty. Patient Y has just been given a large volume of fluid through a drip into their blood.

   (a)

   Compare and explain the changes in ADH release and urine produced by patient X and patient Y, including how this is an example of negative feedback.

   [6 marks]

   (b)

   Describe how you could carry out an investigation to find out how the volume of water a person drinks affects the concentration of the urine they produce over the next few hours, and evaluate one factor that would need to be controlled for the investigation to give a valid comparison.

   [6 marks]

   Total for question 4: 12 marks

End of questions