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CAIE IGCSE Biology 13.1 Excretion in Humans Questions

Practise human-excretion questions on excretory organs, kidney and nephron diagrams, urine formation, deamination and urea removal.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • identify carbon dioxide as a lung excretory product and urea, excess water and ions as kidney excretory products
  • label kidneys, ureters, bladder and urethra and trace urine flow in excretory-system diagrams
  • compare renal artery and renal vein data to identify urea removal by kidneys
  • predict urine-volume changes after water loss, water intake or salt intake
  • identify cortex and medulla on longitudinal kidney sections and label the ureter
  • interpret glomerulus filtration data for glucose, urea, ions and water while retaining proteins and cells
  • explain nephron reabsorption: all glucose but only some water and ions return to blood
  • explain active transport adaptations in tubule cells using mitochondria and microvilli
  • distinguish liver assimilation of amino acids into protein from deamination to urea
  • trace urea from excess amino acids in the liver through blood to kidney excretion
  • explain why urea must be excreted as a toxic metabolic waste

Covered syllabus points

13.1.1—Carbon dioxide is excreted through13.1.2—Kidneys excrete urea and excess water13.1.3—Kidneys, ureters, bladder and urethra13.1.4—Structure of the kidney13.1.5—Structure and function of a nephron13.1.6—Role of the liver in the assimilation13.1.7—Urea is formed in the liver13.1.8—Deamination as the removal13.1.9—Importance of excretion

Question 1

[Maximum number: 14]

The kidney is an organ in the excretory system.

Question (a)

(a)

Describe what is meant by the term excretion.

[ 2 ]

Question (b)

(b)

State the name of the substance excreted by the lungs.
(c) Fig. 4.1 shows a simplified diagram of a cross-section of a kidney.

Fig. 4.1

Fig. 4.1

[ 1 ]

Question (c)

(c)

State the names of the parts labelled P, Q and R in Fig. 4.1.
P

Q

R
(d) Fig. 4.2 shows the structure of a kidney nephron.

Fig. 4.2

Fig. 4.2

[ 3 ]

Question (d)

(d)

Describe and explain the difference in the composition of the fluids in structures X, Y and Z in Fig. 4.2.

[ 6 ]

Question (e)

(e)

The liver is also involved in excretion.

Describe two ways that amino acids are processed in the liver.
1
2

[ 2 ]

Question 2

[Maximum number: 2]

Question (a)

(a)

The carbon dioxide produced during exercise is excreted. Urea is another substance that is excreted.

[ 2 ]

Question (i)

(i)

State the name of the organ that produces urea.

[ 1 ]

Question (ii)

(ii)

State the name of the organ that excretes urea.

[ 1 ]

Question 3

[Maximum number: 1]

The diagram shows the human excretory system.
Which labelled structure is the urethra?

Figure for Question 3 — CAIE IGCSE Biology
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