Chapter 7 Practice Paper: Excretion in Humans — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   Which statement about excretion is correct?

   1. AFaeces are excreted by the large intestine.
   2. BExcretion is the removal of undigested food from the body.
   3. CExcretion is the removal of metabolic waste products from the body.
   4. DOnly the kidneys carry out excretion in humans.
   ( )
2. 2

   In a healthy person, which substances are absent from both the glomerular filtrate and the urine?

   1. Aglucose and amino acids
   2. Bred blood cells and plasma proteins
   3. Curea and salts
   4. Dwater and urea
   ( )
3. 3

   Selective reabsorption in the nephron tubule reclaims

   1. Aall of the glucose and amino acids, and most of the water
   2. Ball of the urea
   3. Cthe plasma proteins
   4. Donly the salts
   ( )
4. 4

   A dialysis machine removes urea from the blood because the dialysis fluid

   1. Acontains a higher urea concentration than the blood
   2. Bcontains no urea, so urea diffuses out of the blood
   3. Cpumps urea out by active transport
   4. Dcontains urea at plasma concentration
   ( )
5. 5

   Blood plasma contains 0.3 g/dm³ of urea; urine contains 20 g/dm³. The best explanation is that

   1. Athe tubule manufactures urea from glucose
   2. Bthe bladder concentrates urea by absorbing water
   3. Cthe glomerulus filters urea faster than water
   4. Dwater is reabsorbed in the tubule while urea is not reabsorbed
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 1

   The described diagram shows the human urinary system: two bean-shaped kidneys, one on each side of the backbone, each joined by a long tube to a single muscular sac, which opens to the outside through a short tube.

   1. (a)

      Name the structures labelled: (i) the bean-shaped organs, (ii) the long tubes, (iii) the muscular sac.

      [3]
   2. (b)

      Name the short tube that carries urine to the outside, and the two blood vessels that carry blood into and out of each kidney.

      [3]
2. 2

   Each kidney contains about a million nephrons, the functional units that produce urine.

   1. (a)

      Name the process that forces fluid from the glomerulus into the Bowman’s capsule, and state what provides the force.

      [2]
   2. (b)

      List three substances present in the glomerular filtrate and two substances that are absent.

      [3]
   3. (c)

      The kidneys filter 180 dm³ of plasma per day but form only 1.5 dm³ of urine. Calculate the percentage of the filtrate that is reabsorbed.

      reabsorbed =%[2]
3. 3

   A patient with kidney failure is treated by dialysis three times a week. Each session lasts four hours, during which blood flows through the machine beside dialysis fluid, separated by a partially permeable membrane. Over one session the patient’s blood urea falls from 1.8 g/dm³ to 0.6 g/dm³.

   1. (a)

      Calculate the percentage decrease in blood urea during one session.

      decrease =%[2]
   2. (b)

      Explain why the dialysis fluid must contain glucose at the same concentration as healthy blood plasma.

      [2]
   3. (c)

      Explain why the treatment must be repeated regularly for the rest of the patient’s life.

      [3]