Cambridge O Level Biology 5090: Human nutrition (5090) – 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 8, Human nutrition, of the Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028 (version 4): sections 8.1 Diet, 8.2 Human digestive system and 8.3 Absorption and assimilation. The syllabus is not tiered. Questions 4, 6, 7 and 12(c) involve calculations; a calculator helps for those.

Learn the content first with the study guide and revision notes. Questions on enzyme pH optima and food tests are in the enzymes practice and biological molecules practice sets, so they are not repeated here.

Questions

1. Name the disease caused by a lack of vitamin C in the diet and describe two of its symptoms. [3]

2. This question is about human teeth.

(a) Name the type of tooth that is pointed and found next to the incisors. [1] (b) Name the hard tissue covering the crown of a tooth, and the part of the tooth that contains nerves. [2] (c) Explain how the action of molars helps chemical digestion. [2]

3. Copy and complete the table for four digestive enzymes. [4]

Enzyme	Substrate	End-product(s)
Amylase	Starch	?
Maltase	?	Glucose
Protease	Protein	?
Lipase	Lipids	?

4. A breakfast cereal label states that it contains 12 mg of iron per 100 g. A student eats a 40 g serving. Assume the student needs 15 mg of iron per day.

(a) Calculate the mass of iron in one serving. [2] (b) Calculate the percentage of the student’s daily iron need supplied by one serving. [2] (c) Explain why a person whose diet lacks iron may feel tired and short of breath. [3]

5. (a) Explain why most food must be digested before it can be absorbed. [2] (b) Describe the difference between physical digestion and chemical digestion. [2]

6. In a model of chewing, a 4 cm cube of potato is cut into 2 cm cubes.

(a) Calculate the total surface area of the potato before and after cutting. [3] (b) Use your answer to explain why chewing speeds up chemical digestion. [2]

7. A student investigates the effect of bile on the digestion of fat in milk. Each tube contains milk, an alkaline solution and an indicator that changes colour when the pH falls.

Tube	Contents added	Time for colour change / s
A	Lipase + bile	125
B	Lipase + water	250
C	Boiled lipase + bile	No change after 600

(a) Explain why the pH falls in tube A. [2] (b) Calculate the rate of reaction, as 1000 / time, for tubes A and B. [2] (c) Explain the difference between the results for tubes A and B. [3] (d) Explain the purpose of tube C. [2] (e) State two variables the student should keep the same. [2]

8. Name the part of the digestive system that:

(a) stores bile [1] (b) produces bile and stores glycogen [1] (c) releases an alkaline secretion containing amylase, protease and lipase [1] (d) carries out egestion. [1]

9. (a) State the function of hydrochloric acid in the stomach. [1] (b) Partly digested food passes from the stomach into the duodenum. Suggest why protein digestion by pepsin slows down in the duodenum while digestion by trypsin speeds up. [3]

10. The lining of the ileum is covered with villi.

(a) Describe the structure of a villus and explain how it is adapted for absorption. [6] (b) State the roles of the capillaries and the lacteal in a villus. [2]

11. (a) Define absorption. [2] (b) Define assimilation and give one example. [2] (c) State the region of the gut where most water is absorbed. [1] (d) Name the blood vessel that carries most absorbed nutrients from the ileum to the liver. [1]

12. A man eats mostly white rice and meat, with very little fruit or vegetables.

(a) Explain why a diet low in fibre may lead to constipation. Refer to peristalsis in your answer. [3] (b) Explain why this diet is not balanced. [2] (c) A fruit contains 200 mg of vitamin C per 100 g. Calculate the mass of this fruit that provides 40 mg of vitamin C. [2]

Answers

1. Scurvy [1]. Any two symptoms: bleeding gums; bleeding under the skin or easy bruising; slow wound healing; tiredness [1] [1]. [3] Examiner insight: “Bleeding” alone is vague; say where (gums, under the skin), and give two separate symptoms rather than one described twice.

2. (a) Canine [1]. (b) Enamel [1]; pulp [1]. (c) Molars grind and crush food into smaller pieces [1], which increases the surface area for enzymes to act on [1]. [5] Examiner insight: Part (c) asks about chemical digestion, so the surface-area link to enzymes is the point; describing grinding alone answers only half.

3. Amylase → maltose [1]. Maltase substrate → maltose [1]. Protease → amino acids [1]. Lipase → fatty acids and glycerol [1]. [4] Examiner insight: Lipase needs both products; “fatty acids” alone is incomplete, and “glucose” for amylase is wrong.

4. (a) 12 × 40 / 100 [1] = 4.8 mg [1]. (b) 4.8 / 15 × 100 [1] = 32% [1]. (c) Iron is needed to make haemoglobin [1]. Less haemoglobin means the blood carries less oxygen [1], so less aerobic respiration in cells releases less energy, and the person breathes harder to get oxygen [1]. [7] Examiner insight: Show the division in (b) clearly, using your own value from (a), so your method can be followed. In (c), the chain must reach oxygen transport, not stop at “iron makes blood”.

5. (a) Food molecules such as starch and protein are large and insoluble [1], so they cannot pass through the gut lining into the blood until broken down into small, soluble molecules [1]. (b) Physical digestion breaks food into smaller pieces without changing the food molecules [1]; chemical digestion breaks large molecules into small molecules (using enzymes) [1]. [4] Examiner insight: Use both ideas, “large” and “insoluble”, in (a); the syllabus definition of physical digestion hinges on “without chemical change”.

6. (a) Before: 6 × 4 × 4 = 96 cm² [1]. After: 8 cubes [1] × 6 × 2 × 2 = 192 cm² [1]. (b) Surface area doubles for the same volume [1], so more food is exposed to enzymes and chemical digestion is faster [1]. [5] Examiner insight: Forgetting that one 4 cm cube makes eight 2 cm cubes is the usual slip; check that total volume (64 cm³) is unchanged.

7. (a) Lipase breaks down fat in the milk [1] into fatty acids (and glycerol), and the fatty acids lower the pH [1]. (b) A: 1000 / 125 = 8.0 [1]. B: 1000 / 250 = 4.0 (arbitrary units) [1]. (c) The rate in A is twice that in B [1]. Bile emulsifies the fat into small droplets [1], giving a larger surface area for lipase, so fatty acids are produced faster [1]. (d) It is a control [1]: it shows that the colour change depends on active lipase, and that bile alone does not digest fat [1]. (e) Any two: volume of milk; volume or concentration of lipase; temperature; volume of bile or water; starting pH or volume of alkaline solution [1] [1]. [11] Examiner insight: In (c), quote the data (twice as fast) and then explain; never write that bile digests or breaks down fat molecules.

8. (a) Gall bladder [1]. (b) Liver [1]. (c) Pancreas [1]. (d) Rectum and anus [1]. [4] Examiner insight: The liver makes bile but does not store it; giving “liver” for (a) is the common confusion.

9. (a) It kills ingested bacteria [1]. (b) The duodenum is not acidic, because the pancreas adds an alkaline secretion [1]. Pepsin works best at the acidic pH of the stomach, so its activity falls [1]. Trypsin works best at the higher pH in the duodenum, so it is more active there [1]. [4] Examiner insight: In (a), “makes the stomach acidic” restates what acid is rather than its function; the syllabus function is killing bacteria.

10. (a) Villi are finger-like projections of the ileum wall that give a large surface area [1]. Epithelial cells carry microvilli, increasing the surface area further [1]. The epithelium is one cell thick [1], so the distance for absorption is short [1]. A dense capillary network carries absorbed nutrients away [1], keeping the concentration gradient steep [1]. (A central lacteal is also a valid structural point in place of any one of these.) (b) Capillaries absorb glucose and amino acids (and water and ions) into the blood [1]; the lacteal absorbs fatty acids and glycerol [1]. [8] Examiner insight: Pair each feature with its effect; a list of features without “so the surface area increases” or “so the distance is short” explains nothing.

11. (a) The movement of nutrients from the intestines into the cells lining the digestive system [1] and then into the blood [1]. (b) The uptake and use by cells of nutrients from the blood [1]; for example, amino acids built into proteins, or glucose stored as glycogen in the liver [1]. (c) Small intestine [1]. (d) Hepatic portal vein [1]. [6] Examiner insight: “The colon” for (c) is wrong: water is absorbed there too, but most is absorbed in the small intestine.

12. (a) Fibre is not digested and adds bulk to food in the gut [1]. Peristalsis is waves of contraction of the circular and longitudinal muscles [1]; with little bulk for the muscles to push against, food moves slowly and faeces become hard [1]. (b) It lacks fibre [1] and vitamin C from fruit and vegetables, risking scurvy (so nutrients are not in the correct proportions) [1]. (c) 40 / 200 × 100 [1] = 20 g [1]. [7] Examiner insight: A balanced diet is about correct proportions of all nutrients, so name the missing nutrients; “not enough vegetables” alone does not say what is missing.

Where marks are usually lost

• Giving glucose as the product of amylase instead of maltose.
• Saying bile digests fat, or calling it an enzyme.
• Swapping the liver (makes bile) and gall bladder (stores bile).
• Describing villus features without stating how each one helps absorption.
• Putting fatty acids and glycerol into the capillaries rather than the lacteal.
• Treating hydrochloric acid’s function as “providing acid” rather than killing bacteria.
• Forgetting that calcium deficiency, as well as vitamin D deficiency, causes rickets.
• Miscounting cubes in surface-area calculations and so getting the wrong total.
• Defining absorption without saying the nutrients reach the blood.

Next steps

• Human nutrition revision notes
• Human nutrition study guide
• Cambridge O Level Biology course hub
• Printable topic checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028, version 4, Cambridge International Education. Topic 8: Human nutrition (8.1 Diet; 8.2 Human digestive system; 8.3 Absorption and assimilation).