Who this is for: Cambridge IGCSE Biology (0610) students who want chemical digestion — enzymes breaking large molecules into small soluble ones — to become a reliable source of marks instead of a confused list of enzyme names.
What query it owns: how to understand and revise chemical digestion in Cambridge IGCSE Biology (0610).
Why this is safe: this page owns the chemical digestion revision-guide angle, while Tutopiya’s Chemical Digestion subtopic page owns the learning resource and the free Chemical Digestion quiz owns the practice.

Chemical digestion is one of the highest-mark topics in Human Nutrition for Cambridge IGCSE Biology (0610). Examiners expect you to match each enzyme to its substrate, product and location — amylase, protease and lipase are non-negotiable. This guide explains the enzyme table, the question types that actually appear, and where to practise each skill.

Key takeaways

• Chemical digestion uses enzymes to break large, insoluble molecules into small, soluble molecules for absorption.
• Amylase → starch → maltose (mouth and small intestine).
• Protease → protein → amino acids (stomach and small intestine).
• Lipase → fats → fatty acids + glycerol (small intestine); bile emulsifies fats first (physical step).

What is chemical digestion in Cambridge IGCSE Biology?

Chemical digestion breaks chemical bonds in large food molecules using digestive enzymes. Starch is broken to maltose (then glucose) by amylase. Proteins are broken to amino acids by protease. Fats are broken to fatty acids and glycerol by lipase. Products must be small and soluble to be absorbed through the wall of the small intestine into the blood.

Read the full enzyme table on Tutopiya’s Chemical Digestion subtopic page before attempting questions.

The core ideas you must master

Enzyme	Substrate	Product	Where produced / works
Amylase	Starch	Maltose	Salivary glands (mouth); pancreas (small intestine)
Protease	Protein	Amino acids	Stomach (pepsin); pancreas (small intestine)
Lipase	Fats (lipids)	Fatty acids + glycerol	Pancreas (small intestine)

How to answer chemical digestion questions — step by step

1. Name the enzyme — amylase, protease or lipase unless the stem specifies.
2. State substrate and product — starch → maltose, protein → amino acids, fats → fatty acids + glycerol.
3. Give the location — mouth, stomach or small intestine.
4. For explain questions — enzyme breaks bonds → small soluble molecules → can be absorbed.
5. Link stomach acid — HCl provides optimum pH for protease in the stomach.
6. Contrast with physical digestion — enzymes change molecules chemically; teeth and bile do not.

Test yourself with the free Chemical Digestion quiz.

Chemical digestion in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical chemical digestion stem
State	Short fact	”State the product of fat digestion.”
Name	Identify enzyme	”Name the enzyme that digests starch.”
Describe	What happens	”Describe chemical digestion of protein in the stomach.”
Explain	Reason or mechanism	”Explain why digested food must be soluble.”
Complete	Fill table	”Complete the table: enzyme, substrate, product.”

Worked exam-style stems (how to answer the wording)

1. “Name the enzyme that digests starch and state its product.” Amylase — breaks starch into maltose. Reward: correct enzyme and product.

2. “Describe the chemical digestion of protein in the stomach.” Protease (pepsin) breaks protein into amino acids; hydrochloric acid provides acidic pH for the enzyme. Reward: enzyme + product + role of acid.

3. “Explain why food must be digested before absorption.” Large insoluble molecules cannot pass through the gut wall; digestion produces small soluble molecules that can be absorbed into the blood. Reward: insoluble → soluble + absorption link.

Complete-the-table stems: enzyme revision drill

Table-completion questions are the most common chemical digestion format in Cambridge IGCSE Biology (0610). Practise filling every cell without looking.

Enzyme	Substrate	Product	Optimum location
Amylase	Starch	Maltose	Mouth / small intestine
Protease	Protein	Amino acids	Stomach / small intestine
Lipase	Fats	Fatty acids + glycerol	Small intestine
Maltase	Maltose	Glucose	Small intestine

4. “Complete the table to show the enzyme, substrate and product for the digestion of fats.” Lipase | fats | fatty acids and glycerol. Reward: all three cells correct; bile emulsification mentioned in explain follow-ups.

Chemical digestion links to Physical Digestion, Digestive System and Enzymes. The Cambridge IGCSE Biology resource hub links every Human Nutrition resource.

Common mistakes students make

• Saying amylase breaks starch directly to glucose — maltose first (maltase completes to glucose).
• Confusing protease (protein → amino acids) with lipase (fats → fatty acids + glycerol).
• Placing lipase in the stomach — it works in the small intestine.
• Omitting fatty acids and glycerol as fat digestion products.
• Describing bile as a lipase — bile emulsifies; lipase digests chemically.

When you need more support

If enzyme-table questions keep losing marks, work through the Chemical Digestion quiz and Enzymes quiz, then book a Cambridge IGCSE Biology tutor.

Frequently asked questions

Must I know all three digestive enzymes? Yes — amylase, protease and lipase with substrate, product and location.

Is maltose the final starch product? In the syllabus, amylase produces maltose; maltase then breaks maltose to glucose in the small intestine.

Where is lipase produced? Pancreas — works in the small intestine on emulsified fats.

How do I revise chemical digestion effectively? Memorise the enzyme table, practise complete-table stems, then take the Chemical Digestion quiz.

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