Question 1
Paper 4 short-answer style1 markState where most of the absorption of digested food takes place. (1 mark)
Model answer
In the small intestine.
Why this scores
One mark for 'small intestine'.
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Detailed notes on Human Nutrition for Cambridge IGCSE Biology, covering key concepts, explanations, examples, and exam-focused revision points.
After digestion, small soluble nutrients enter the blood (and lymph) via the small intestine. The liver gets the first look at them.
Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).
Small intestine = nutrient absorption. Large intestine = water absorption.
Different parts of the gut do different jobs.
Small intestine (~6 metres long).
Large intestine (~1.5 m).
Worked qualitative. Why does diarrhoea cause dehydration?
Cambridge tip. "Absorption" without specifying which gut loses you marks. Always say "small intestine" for nutrients and "large intestine" for the last of the water.
Long + folded + villi + microvilli = enormous surface area.
Adaptations of the SMALL INTESTINE:
1. Length. ~6 m. More length = more time for digestion AND more surface area.
2. Internal folds. The wall folds inward (circular folds) — multiplies surface area.
3. Villi. Finger-like projections covering the inside surface — millions of them. Each villus is ~1 mm long. They multiply surface area MASSIVELY.
4. Microvilli. Tiny projections on EACH epithelial cell of every villus. Multiply surface area AGAIN.
Total surface area: ~250 m² — about the size of a tennis court.
Adaptations of a single VILLUS:
| Feature | Why |
|---|---|
| Long, finger-shaped | Increases surface area. |
| Thin epithelium (1 cell thick) | Short DIFFUSION distance. |
| Capillary network inside | Carries absorbed nutrients away — keeps a steep gradient. |
| Lacteal in centre | Absorbs products of fat digestion (lymph route). |
| Microvilli on cells | Even more surface area + active transport. |
How nutrients enter:
Worked qualitative. Why is the wall of the small intestine "one cell thick"?
Cambridge tip. When asked "how is the small intestine adapted", give 4 features each PAIRED with a reason. "Long" alone = 0; "long, providing a large surface area" = 1.
Hepatic portal vein delivers nutrient-rich blood to the liver. Liver controls glucose, deaminates amino acids, detoxifies, makes bile.
The route.
Blood capillaries in villi → small veins → HEPATIC PORTAL VEIN → LIVER → hepatic vein → vena cava → rest of body.
So the liver gets FIRST LOOK at everything you absorb.
Roles of the liver in assimilation:
1. Glucose regulation.
2. Amino acid management.
3. Detoxification.
4. Bile production.
5. Iron storage.
6. Stores fat-soluble vitamins (A, D).
Worked qualitative. A patient drinks heavily for years and has yellow skin (jaundice). What's happening?
Cambridge tip. When asked about the role of the liver, list AT LEAST THREE: glucose, amino acids, bile. Forgetting one means losing marks.
Verbatim phrases and definitions Cambridge mark schemes credit.
Absorption appears every Paper 4 (5-7 marks: villus structure, role of liver, deamination). Examiner reports flag students saying 'large intestine absorbs nutrients', forgetting the lacteal for fats, and missing the hepatic portal vein.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (7.5); 0610/42 May/Jun 2024 — Q6 (absorption); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.
Step-by-step solutions to past-paper-style questions on absorption, written exactly the way a tutor would explain them at the board.
Question
State where each is absorbed: glucose, amino acids, fatty acids + glycerol, and water.
Step-by-step solution
Step 1
Glucose — in the small intestine, into the blood capillaries.
Step 2
Amino acids — in the small intestine, into the blood capillaries.
Step 3
Fatty acids + glycerol — in the small intestine, into the lacteal (lymph).
Step 4
Water — most in the small intestine; the remainder in the large intestine.
Answer
Glucose and amino acids → blood (small intestine). Fatty acids + glycerol → lacteal/lymph (small intestine). Water → small intestine and large intestine.
Question
Name the structure in the small intestine that: (a) increases the surface area; (b) absorbs the products of fat digestion; (c) carries absorbed glucose away from the villus.
Step-by-step solution
Step 1
(a) Increases surface area → villi (and the tiny microvilli on their cells).
Step 2
(b) Absorbs fatty acids and glycerol → the lacteal (a lymph capillary).
Step 3
(c) Carries glucose away → the blood capillaries in the villus.
Answer
(a) Villi (and microvilli); (b) lacteal; (c) blood capillaries.
Examiner tip
Fats go into the lacteal (lymph); glucose and amino acids go into the blood capillaries.
Question
Describe four adaptations of a villus that help absorption.
Step-by-step solution
Step 1
Long, finger-like shape (with tiny microvilli on the cells): greatly increases the SURFACE AREA for absorption.
Step 2
Thin wall (one cell thick): short diffusion distance for nutrients into the blood.
Step 3
Rich blood supply (capillary network): carries absorbed nutrients away quickly, maintaining a steep concentration gradient.
Step 4
Lacteal inside: absorbs the products of fat digestion (fatty acids and glycerol).
Answer
Villi are long and thin-walled, with a rich blood supply and a lacteal; microvilli further increase the surface area — all speeding up absorption.
Examiner tip
Pair each adaptation with its reason. List four features and four reasons.
Question
Explain how the small intestine as a whole is adapted for the efficient absorption of digested food.
Step-by-step solution
Step 1
It is very long, giving plenty of time and area for absorption as food passes along.
Step 2
Its inner surface is folded and covered in millions of villi, and the villus cells have microvilli — together giving an enormous surface area.
Step 3
The villus wall is one cell thick, giving a short diffusion distance into the blood.
Step 4
Each villus has a rich blood supply and a lacteal that quickly carry absorbed substances away, keeping a steep concentration gradient.
Answer
The small intestine is long and lined with villi and microvilli (huge surface area), has thin walls (short diffusion distance), and a good blood and lymph supply (steep gradient) — making absorption fast and efficient.
Question
After absorption, blood from the small intestine goes to the liver first. Give three things the liver does with the absorbed nutrients.
Step-by-step solution
Step 1
Absorbed nutrients are carried in the blood via the hepatic portal vein to the liver first.
Step 2
Glucose regulation: the liver helps control blood glucose, storing excess glucose as glycogen and releasing glucose when needed.
Step 3
Amino acids: the liver keeps what is needed and deaminates the excess — removing the amino group to form urea, which the kidneys excrete.
Step 4
Other roles: it breaks down toxins (e.g. alcohol) and stores some vitamins and iron.
Answer
Nutrient-rich blood goes via the hepatic portal vein to the liver, which regulates blood glucose (glycogen store), deaminates excess amino acids (forming urea) and breaks down toxins.
Question
Explain how the cells of the small intestine ensure that almost all the glucose is absorbed, even when the concentration in the gut falls very low.
Step-by-step solution
Step 1
At first, glucose is at a higher concentration in the gut than in the blood, so it is absorbed by diffusion down the concentration gradient.
Step 2
As absorption continues, the glucose concentration in the gut falls below that in the blood, so diffusion can no longer move it in.
Step 3
The villus cells then use active transport to take up the remaining glucose against the concentration gradient, using energy from respiration.
Step 4
This ensures that virtually all the glucose is absorbed and little is lost in the faeces.
Answer
Glucose is first absorbed by diffusion (gut concentration higher), then by active transport once the gut concentration falls below the blood — so almost all the glucose is taken up.
Examiner tip
The key insight: diffusion alone would stop once concentrations equalise; active transport completes the job, which is why villus cells have many mitochondria.
High-scoring sample answers for absorption on the Cambridge IGCSE 0610 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
State where most of the absorption of digested food takes place. (1 mark)
Model answer
In the small intestine.
Why this scores
One mark for 'small intestine'.
State two features of a villus that increase the rate of absorption. (2 marks)
Model answer
A villus has a large surface area (it is long and finger-like, with microvilli) and a thin wall (one cell thick), giving a short diffusion distance. (A good blood supply is also accepted.)
Why this scores
Any two of: large surface area; thin/one-cell-thick wall; good blood supply; lacteal. Naming the feature is enough here.
Explain how three features of a villus adapt it for efficient absorption. (3 marks)
Model answer
A villus is long and finger-shaped, with microvilli, giving a large surface area for absorbing nutrients. Its wall is only one cell thick, giving a short diffusion distance into the blood. It has a rich network of blood capillaries that quickly carry absorbed nutrients away, maintaining a steep concentration gradient for fast absorption.
Why this scores
Three marks, each a feature linked to its effect: large surface area; thin wall/short distance; good blood supply/steep gradient.
Explain how the small intestine is adapted for the absorption of digested food. (4 marks)
Model answer
The small intestine is very long, providing a large area and time for absorption. Its inner wall is covered in millions of villi, and the cells of the villi have microvilli, giving a very large surface area. The wall of each villus is only one cell thick, so there is a short diffusion distance for nutrients to reach the blood. Each villus also has a good blood supply and a lacteal, which carry the absorbed substances away and keep a steep concentration gradient.
Why this scores
Four marks: long; villi + microvilli for large surface area; thin (one-cell) wall/short distance; good blood supply/lacteal.
Explain how glucose is absorbed from the small intestine into the blood. (5 marks)
Model answer
When the concentration of glucose in the small intestine is higher than in the blood, glucose is absorbed by diffusion down its concentration gradient, across the thin wall of the villus into the blood capillaries. As more glucose is absorbed, its concentration in the gut falls below that in the blood, so diffusion can no longer move it across. The cells of the villus then use active transport to take up the remaining glucose against the concentration gradient, using energy from respiration (which is why these cells contain many mitochondria). In this way almost all of the glucose is absorbed into the blood.
Why this scores
Five marks: diffusion while gut concentration is higher; down the gradient; gut concentration later falls below blood; active transport against the gradient; uses energy from respiration. Both mechanisms must be explained.
Describe what happens to glucose and amino acids after they have been absorbed, including the role of the liver. (6 marks)
Model answer
After absorption into the blood capillaries of the villi, the glucose and amino acids are carried in the blood through the hepatic portal vein straight to the liver. The liver helps to regulate the blood glucose concentration: if there is too much glucose, the liver converts the excess into glycogen for storage, and it converts glycogen back to glucose when the blood level falls. With the amino acids, the liver keeps those the body needs for making new proteins (assimilation in the cells), and deaminates the excess — removing the amino group to form urea, which is carried to the kidneys and excreted in the urine, while the rest of the molecule can be used in respiration. In this way the absorbed nutrients are regulated and either stored, used by the cells, or have their waste removed.
Why this scores
Up to 6 marks: nutrients travel via the hepatic portal vein to the liver; liver regulates blood glucose; excess glucose stored as glycogen; amino acids used for proteins (assimilation); excess amino acids deaminated; forming urea excreted by the kidneys.
Definitions to memorise and the exact keywords mark schemes credit for absorption answers — sharpened from recent examiner reports for the 2026 0610 sitting.
Finger-like projection on the inner wall of the small intestine. Increases surface area for absorption.
Tiny projections on the surface of villus epithelial cells. Further increase the surface area.
Lymph capillary inside each villus. Absorbs the products of fat digestion (fatty acids + glycerol).
Vein carrying nutrient-rich blood from the small intestine directly to the liver.
Removal of the amino group (-NH₂) from an excess amino acid, in the liver. Produces urea, which the kidneys excrete.
The traps other students keep falling into on absorption questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.
Why it happens
The large intestine's main role IS water absorption.
How to avoid it
MOST water is absorbed in the SMALL intestine. The large intestine absorbs the REMAINING water from the waste material.
Why it happens
Sugars and amino acids do, so fats seem similar.
How to avoid it
Fatty acids and glycerol enter the LACTEAL (lymph) first. The lymph eventually drains into the blood, but the initial path is different.
Why it happens
Cells need glucose for respiration.
How to avoid it
The first stop is the LIVER (via the hepatic portal vein). The liver regulates blood glucose before it is sent on, and deaminates excess amino acids.
The things students keep getting wrong in this sub-topic, answered.