1 The diagram shows the teeth in the lower jaw of a human. X (a) Name the type of tooth labelled X and describe one function of this type of tooth. type of tooth … function … … [2] (b) Food can be sweetened using honey or sugar. The graph shows how the pH of saliva in the mouth changes with time after eating food sweetened with honey or sugar. 3.0 4.0 5.0 H of aliva 6.0 7.0 0 5 10 15 20 time after eating / minutes 25 30 35 40 honey key sugar (i) State the lowest pH of saliva in the mouth after eating food sweetened with honey. … [1] (ii) It takes more time for saliva to return to pH 7.0 after eating food sweetened with sugar than after eating food sweetened with honey. State how much more time it takes for the pH to return to 7.0. … [2] (c) Dental decay is likely to occur when the pH of saliva falls below 5.5. (i) Use information from the graph to explain whether sweetening food with honey or with sugar is more likely to lead to dental decay. … … … … … … [2] (ii) State two ways to prevent dental decay. 1 … 2 … [2] (iii) A person with dental decay may also have gums that bleed. This makes it more likely that bacteria found in the mouth will enter the circulatory system. Bacteria in the circulatory system can cause the blood to clot. Small blood clots may move through the circulatory system to the coronary arteries. Suggest and explain possible health problems that this may cause. … … … … … … … … [4] [Total: 13]

1(a)(i) (type of tooth) (function) 1 canine ; 2 tearing / ripping / piercing ; 2 Ig chewing 1(b)(i) 4.75 ; 1 1(b)(ii) 1 15 ; 2 minutes / min ; 2 1(c)(i) 1 lower pH / more acidic / any pH between 3.5 and 4.74 ; 2 longer time / any time between 25 and 35 minutes ; 2 1(c)(ii) 1 brushing / cleaning / toothpaste ; 2 flossing / mouthwash ; 3 fluoride ; 4 avoid sugar AW / use artificial sweetener ; 5 use honey rather than sugar ; 2 Ig dental check-ups 1(c)(iii) 1 heart attack / angina AW / breathlessness ; 2 less ability AW of heart to + contract / pump ; 3 less blood to + body / tissues / organs or any named ; 4 less oxygen / less glucose to + body / tissues / organs or any named ; 5 anaerobic respiration / less aerobic respiration ; 6 lactic acid ; 7 less ability AW to carry out / fatigue + physical activity ; 4

2 The diagram shows the circulatory system of a fish. The lungs of a human and the gills of a fish both have a large surface area for gas exchange. capillaries of gills aorta heart capillaries of body tissues (a) (i) State two differences between the structure of the heart of a fish and the structure of the heart of a human. 1 … … 2 … … [2] (ii) Draw a ring around the correct words to complete the sentence below. higher than the same as lower than The pressure of blood in the aorta of a fish will be … the pressure of blood in the aorta of a human. [1] (b) The photograph shows an Antarctic icefish. The blood of Antarctic icefish is colourless. (i) State which component of human blood is not present in the blood of an Antarctic icefish. … [1] Antarctic icefish live in the Antarctic Ocean where the water temperature is very cold. Aerobic respiration is an enzyme-controlled reaction. More oxygen is able to dissolve in water at a lower temperature. Antarctic icefish have a larger heart, wider blood vessels and a greater volume of blood than fish of the same size that live in warmer water. (ii) Suggest how Antarctic icefish with colourless blood are able to survive in the low temperatures of the Antarctic Ocean. … … … … … … … … … … [5] [Total: 9]

2(a)(i) fish + 2 chambers AW OR human + 4 chambers AW ; fish + 2 valves AW OR human + 4 valves AW ; fish + 2 blood vessels AW OR human + 4 blood vessels AW ; fish + chambers similar size OR human + chambers different sizes ; 2 2(a)(ii) lower than ; 1 A any clear reference only to lower than 2(b)(i) red blood cells / erythrocytes / haemoglobin ; 1 2(b)(ii) less + aerobic respiration ; enzyme reactions + slower ; less + oxygen needed ; more oxygen + absorbed AW by fish ; more oxygen + plasma ; more blood / more oxygen + supplied / taken / pumped ; (to) organs / tissues / cells ; 5

4 Cardiopulmonary resuscitation (CPR) is a first aid procedure. Air is forced into a patient’s lungs by another person. The heart is made to pump blood by repeated compression of the patient’s chest over the heart. A person performing CPR on a patient is shown in the diagrams. repeated compression of chest air forced into lungs (a) (i) State what will be seen to happen to the patient’s chest when air is forced into the lungs. … [1] (ii) Name, in the correct order, the tubes through which air will travel from the patient’s mouth to the alveoli of the lungs. … … … [2] (iii) The air forced into the patient’s lungs has different concentrations of gases compared to the air the patient would normally breathe in. State two differences in the concentrations of gases. … … … [2] (b) Explain how each action of the CPR procedure will benefit the patient: air forced into the patient’s lungs … … … … repeated compression of the patient’s chest. … … … … [4] [Total: 9]

4(a)(i) rises / expands AW ; 1 4(a)(ii) ALL THREE from the list below = 2 marks ;; OR ANY ONE or TWO from the list below = 1 mark ; left box = larynx / trachea middle box = bronchi / bronchus right box = bronchiole(s) 2 left box Ig windpipe 4(a)(iii) air forced into the lungs has ... 1 less oxygen ; 2 more carbon dioxide ; 3 more water vapour ; 2 4(b) 1 oxygen + lungs / alveoli / air sacs ; 2 oxygen + blood / red blood cells / RBC / erythrocytes / haemoglobin ; 3 diffusion ; 4 high to low concentration / down concentration gradient ; 5 blood from + left ventricle ; 6 blood to + organs / tissues / cells ; 7 aerobic respiration ; 8 re-start the heart ; 4

8 State the functions of the human liver and explain the importance to a person of each function. … … … … … … … … … … … … … … … … … … … … [Total: 10]

7(b) 1 hinge ; 1 any three from: 2 contracts ; 3 pulls / jerks ; 4 radius + ulna ; 5 up / towards humerus / away from / flexion ; 3 8 1 bile ; 2 emulsifies lipids / large to small lipid droplets + increased surface area ; 3 increased + digestion AW of lipids / activity of lipase ; 4 deamination / metabolism + amino acids ; 5 formation AW of urea ; 6 breakdown / removes + alcohol / lactic acid ; 7 breakdown / removes + hormones / named hormone ; 8 prevents + continued effect of hormone ; 9 glucose + glycogen ; 10 energy / glycogen + store ; 11 (glycogen) insoluble ; 12 no change to water potential of cells ; 13 high metabolic rate / high rate of respiration + heat production ; 14 breakdown of + haemoglobin / red blood cells / RBC / erythrocytes ; 15 iron ; 16 storage of vitamins ; 10 To earn marks, you must state a function of the liver and then explain its importance to a person. Examples include bile production for fat emulsification and digestion, deamination of amino acids to form urea, breakdown of toxins like alcohol, conversion of glucose to glycogen for energy storage, or breakdown of red blood cells and storage of vitamins.

5 Hydrogencarbonate indicator changes colour according to the concentration of carbon dioxide present. The table shows how hydrogencarbonate indicator changes colour. colour of hydrogencarbonate indicator concentration of carbon dioxide orange atmospheric carbon dioxide concentration yellow higher than atmospheric carbon dioxide concentration purple lower than atmospheric carbon dioxide concentration Four test-tubes were set up under different conditions. The colour of hydrogencarbonate indicator in each test-tube at the start of the experiment and after 1 hour is also shown. Which test-tube shows that the rates of photosynthesis and respiration are the same? D in light orange to yellow C in light orange to purple B in dim light stays orange A in darkness orange to yellow stopper hydrogen- carbonate indicator aquatic snail aquatic plant stopper hydrogen- carbonate indicator aquatic plant foil

Answer: B To earn the mark, a student must identify the test-tube where the hydrogencarbonate indicator stays orange, indicating that the carbon dioxide concentration remains atmospheric.

Cambridge O Level Biology · 5090

O-Level Biology (5090) Respiration past paper questions

Revise O-Level Biology (5090) — Respiration with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

59 free questions from 2017–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Respiration in O-Level Biology 5090 exams, 2020–2025

Across 2020–2025, Respiration accounted for 75 questions worth 371 marks in Cambridge O Level Biology (5090) papers.

By year
Year	Questions	Marks
2020	10	29
2021	13	59
2022	14	82
2023	13	31
2024	9	93
2025	16	77

Most-tested subtopics

Appears in

Paper 1 · 49 qs
Paper 2 · 18 qs
Paper 3 · 4 qs
Paper 4 · 4 qs

All most-tested Biology topics

2021 May/Jun · Paper 2 · Q1 · 13 marks
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2021 Oct/Nov · Paper 2 · Q2 · 9 marks
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2021 May/Jun · Paper 2 · Q4 · 9 marks
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2021 May/Jun · Paper 2 · Q8 · 10 marks
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2021 May/Jun · Paper 1 · Q5 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q5
Answer: B
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