S2 Science: Digestion And Nutrients (Paper 4 (error Clinic))

S2 Science: Digestion and Nutrients (Paper 4 (error clinic))

2026-11-14

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Tutor Prep Guide · The role of each part of the digestive tract, enzyme action and temperature, bile emulsifying fats, absorption by villi, and food tests for starch, reducing sugars, protein and fat

S2 Science: Digestion and Nutrients (Paper 4 (error clinic))

This paper corrects ten common errors about digestion and nutrition, covering bile, enzymes, fibre, food tests and the site of absorption.

Direct answers　Bile emulsifies rather than splits, enzymes are reusable, digestion starts in the mouth and finishes in the small intestine, fibre is useful, iodine matches starch, Benedict matches reducing sugar, biuret matches protein, and the colon only takes up water.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S2 Science: Digestion and Nutrients
Level	S2

02　Questions (10 items)

FoundationBile is said to contain a fat digesting enzyme. What is wrong?
FoundationAn enzyme is said to be used up after each reaction. What is wrong?
FoundationDigestion is said to happen only in the stomach. What is wrong?
IntermediateFibre is said to be useless because it cannot be digested. What is wrong?
IntermediateIodine is said to test for glucose. What is wrong?
IntermediateBiuret solution is said to test starch. What is wrong?
ChallengeFat is said to be absorbed without being broken down. What is wrong?
ChallengeEnzyme activity is said to be the same at any temperature. What is wrong?
ChallengeVitamins are said to supply energy. What is wrong?
Error redoThe colon is said to be the main place where nutrients are absorbed. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	Bile has no enzyme; it only emulsifies fat into small droplets, and lipase does the splitting	Emulsifying is a physical change and splitting is a chemical one, so the two must be kept apart.
2	An enzyme is a catalyst whose structure and amount are unchanged, so it works repeatedly	The body still makes new enzymes because old ones wear out, not because each reaction consumes them.
3	Digestion starts in the mouth and most chemical digestion and absorption happen in the small intestine	The mouth has amylase and the small intestine receives many enzymes, so the stomach is only one stage.
4	Fibre adds bulk, stimulates gut movement and helps waste pass, reducing constipation	Not being digested is exactly what lets fibre reach the colon and do its job.
5	Iodine tests starch, while reducing sugar needs Benedict solution and heat	Learn the pairs: iodine for starch, Benedict for reducing sugar and biuret for protein.
6	Biuret tests protein and turns purple, while starch is tested with iodine	Remember each reagent with its colour, so a change of wording in the question does not mislead you.
7	Fat must first be split by lipase into glycerol and fatty acids before it can cross the gut wall	Fat molecules are large and insoluble, so without splitting they cannot enter the absorbing cells.
8	Activity peaks near 37 degrees, falls when it is colder, and the enzyme denatures above about 60 degrees	Temperature changes both how often enzyme meets substrate and the shape of the enzyme, and both have limits.
9	Vitamins supply no energy; carbohydrate, protein and fat do	Vitamins help enzymes work and keep body functions going, so only tiny amounts are needed but they cannot be left out.
10	Nutrients are absorbed mainly in the small intestine, while the colon absorbs mainly water and minerals	The small intestine has villi and a huge surface area while the colon has none, so their absorbing power is very different.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For digestion questions ask three things: whether the question is about structure, an enzyme or a nutrient, which part of the tract the reaction happens in, and whether the colour change of a food test is being used.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.