Cambridge IGCSE Biology 0610: Excretion in humans – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover topic 13, Excretion in humans, of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028: section 13.1, outcomes 1–9. Questions 1, 2, 3 and 9 use Core content only, so every candidate should attempt them. Questions marked (Extended) test Supplement content, which is examined only on Papers 2 and 4. A calculator is useful for questions 6, 9 and 10.

Before you start, you may want the excretion study guide or the excretion revision notes. The Cambridge IGCSE Biology hub lists every topic, and the printable 0610 checklist lets you tick off each outcome. The free Core diagnostic and Extended diagnostic show which topics to prioritise.

Questions

1. Carbon dioxide is an excretory product.

(a) State the organ through which carbon dioxide is excreted. [1] (b) Name the process in cells that produces carbon dioxide. [1]

2. Name the structure of the urinary system that:

(a) stores urine [1] (b) carries urine from a kidney to the bladder [1] (c) carries urine from the bladder to the outside of the body. [1]

3. (a) Define the term excretion. [2] (b) Explain why the removal of faeces from the body is not an example of excretion. [1]

4. (Extended) A kidney is cut in half lengthways to show its internal structure.

(a) Name the darker outer region of the kidney. [1] (b) Name the inner region, made of cone-shaped sections. [1] (c) Name the tube that leaves the kidney and carries urine away from it. [1]

5. (Extended) Outline how urine is formed in a nephron. [4]

6. (Extended) In one adult, the kidneys filter 180 dm³ of fluid from the blood each day. The same person produces 1.5 dm³ of urine each day.

(a) Calculate the percentage of the filtered volume that is reabsorbed into the blood. Give your answer to three significant figures. [2] (b) The glucose concentration in this person’s blood plasma and in their filtrate is 1.0 g per dm³. Calculate the mass of glucose filtered in one day. [1] (c) State the mass of glucose in this person’s urine and explain your answer. [2]

7. (Extended) Amino acids absorbed after a meal are carried to the liver.

(a) Describe the role of the liver in the assimilation of amino acids. [1] (b) Describe what happens to amino acids during deamination. [2] (c) Name the excretory product formed by deamination. [1]

8. (Extended) A person’s kidneys stop working. Suggest what happens to the concentration of urea in their blood and explain why this is harmful. [3]

9. On Monday a student drinks a large volume of water and produces 2.5 dm³ of urine. On Tuesday she drinks much less and produces 0.8 dm³ of urine.

(a) Suggest why she produced a larger volume of urine on Monday. [2] (b) Calculate the percentage decrease in urine volume from Monday to Tuesday. [2]

10. (Extended) The table shows the concentration of four substances in the blood plasma, in the filtrate at the start of a nephron, and in the urine of a healthy person.

Substance	Plasma / g per dm³	Filtrate / g per dm³	Urine / g per dm³
Protein	70	0	0
Glucose	0.9	0.9	0
Urea	0.3	0.3	20
Sodium ions	3.3	3.3	5.0

(a) Explain why there is no protein in the filtrate. [2] (b) Explain the difference between the glucose concentration in the filtrate and in the urine. [2] (c) Calculate how many times more concentrated urea is in the urine than in the plasma. Give your answer to three significant figures. [2] (d) Explain why the urea concentration in the urine is much higher than in the filtrate. [2]

11. (Extended) A meal contains more protein than the body needs. Describe the pathway by which the nitrogen in this protein ends up leaving the body in urine. Start with digestion of the protein and end when the urine leaves the body. [8]

Answers

1. (a) The lungs [1]. (b) Respiration (aerobic respiration) [1]. Examiner insight: Structured questions usually accept only the named organ; “the nose” or “the mouth” gains nothing, because gas exchange with the blood happens in the lungs.

2. (a) The bladder [1]. (b) A ureter [1]. (c) The urethra [1]. Examiner insight: Spelling that could be either word (for example “urether”) is normally not credited when the two answers are different structures, so learn to spell ureter and urethra accurately.

3. (a) The removal of the waste products of metabolism [1] and of substances in excess of requirements [1]. (b) Faeces are mainly undigested food, which has never been part of the body’s metabolism, so their removal is egestion [1]. Examiner insight: A definition question awards one mark per idea, so “removal of waste” alone gets at most one of the two marks; both “metabolism” and “in excess of requirements” are needed for full marks.

4. (a) Cortex [1]. (b) Medulla [1]. (c) Ureter [1]. Examiner insight: In an “identify on a diagram” version of this question, the mark depends on where your label line ends; the line must touch the named region, not a boundary.

5. Water, glucose, urea and ions are filtered from the blood at the glomerulus [1]. All of the glucose is reabsorbed into the blood [1]. Most of the water and some of the ions are reabsorbed [1]. The remaining liquid is urine, containing urea, excess water and excess ions [1]. Examiner insight: The syllabus states that details of these processes are not required, so marks go on the named substances and the words all / most / some; a long account of mechanisms earns no extra credit if these points are missing.

6. (a) Volume reabsorbed = 180 − 1.5 = 178.5 dm³; percentage = (178.5 ÷ 180) × 100 [1] = 99.2% [1]. (b) 1.0 × 180 = 180 g [1]. (c) 0 g (no glucose in the urine) [1], because all of the filtered glucose is reabsorbed into the blood along the nephron [1]. Examiner insight: In a two-mark calculation a correct final answer normally earns both marks, but if the answer is wrong the method mark can still be given for the correct expression shown in working, so always write the working down.

7. (a) The liver converts amino acids into proteins (for example plasma proteins such as fibrinogen) [1]. (b) The nitrogen-containing part of each amino acid is removed [1], in the liver, and is used to form urea [1]. (c) Urea [1]. Examiner insight: “Proteins are broken down” describes digestion, not deamination, and scores nothing in (b); the answer must refer to amino acids and to the nitrogen-containing part.

8. The urea concentration in the blood increases (urea builds up) [1] because it is no longer filtered out and excreted by the kidneys [1]. Urea is toxic, so a high concentration damages cells [1]. Examiner insight: For “suggest and explain” answers, the prediction (increase) and the reason (toxic, damages cells) are separate marking points; stating only that it is “bad for the body” does not earn the toxicity mark.

9. (a) She took in more water than the body needed [1], so the kidneys excreted the excess water, giving a larger volume of urine [1]. (b) Decrease = 2.5 − 0.8 = 1.7 dm³; percentage decrease = (1.7 ÷ 2.5) × 100 [1] = 68% [1]. Examiner insight: Percentage change must be divided by the original value (Monday); dividing by 0.8 gives 212.5%, which cannot earn the accuracy mark and is unlikely to earn the method mark.

10. (a) Protein molecules are too large [1] to be filtered out of the blood at the glomerulus, so they stay in the blood [1]. (b) Glucose is filtered, so the filtrate has the same concentration as plasma [1]; all of the glucose is then reabsorbed into the blood along the nephron, so urine has none [1]. (c) 20 ÷ 0.3 [1] = 66.7 times [1]. (d) Most of the water in the filtrate is reabsorbed [1], but urea is not reabsorbed like glucose, so the urea is left in a much smaller volume of water [1]. Examiner insight: In data questions, answers that quote figures from the table (“0.9 g per dm³ in filtrate, 0 in urine”) alongside the explanation are safer, because “explain the difference” expects the difference to be identified as well as explained.

11.

• The protein is digested into amino acids [1].
• Amino acids are absorbed into the blood in the small intestine [1].
• They are carried in the blood to the liver [1].
• Excess amino acids are deaminated: the nitrogen-containing part is removed [1].
• The nitrogen-containing part is used to form urea in the liver [1].
• Urea is carried in the blood plasma to the kidneys [1].
• Urea is filtered from the blood at the glomerulus and is not reabsorbed like glucose, so it stays in the urine [1].
• Urine passes down the ureter to the bladder and leaves the body through the urethra [1].

[8] Examiner insight: Long “describe the pathway” answers are marked point by point, so keep the steps in the correct order and give each organ its own sentence; naming the kidney as the place where urea is made loses a mark even if everything else is correct.

Where marks are usually lost

• Naming faeces as an excretory product, or defining excretion without “metabolism” or “in excess of requirements”.
• Swapping ureter and urethra, or misspelling them so the examiner cannot tell which you mean.
• Saying the kidneys make urea; the liver makes it and the kidneys excrete it.
• Saying glucose is not filtered, instead of filtered and then all reabsorbed.
• Writing “some” of the water or “all” of the ions for reabsorption.
• Calculating percentage change by dividing by the new value instead of the original value.
• Describing deamination as breaking down protein rather than removing the nitrogen-containing part of amino acids.
• Explaining why excretion matters without saying urea is toxic.
• Reading only one column of a data table and not comparing plasma, filtrate and urine.

Next steps

• Recap with the excretion revision notes.
• Re-read any weak section in the excretion study guide.
• Move on to the coordination and response study guide.
• See every topic on the Cambridge IGCSE Biology hub.
• Tick off outcomes on the printable 0610 checklist.
• Try the free Core diagnostic or Extended diagnostic, or browse all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028 (Version 3), published by Cambridge University Press & Assessment (Cambridge International Education). Topic 13, section 13.1 Excretion in humans.