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IGCSE · Cambridge (CIE) · 0973

Explain lipase digestion of fats and oils

Name the enzyme and the school-level lipid products.

Chemical digestion · Cambridge IGCSE 0973 · B7.4
Exam scope and assessment notes

Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.

Before you begin

  • Recall large and small nutrient molecules, cell membranes and enzyme specificity.
  • Use the stated diagram keys and evidence; models are not to scale.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

Which enzyme acts on fats and oils?

What you will learn

  • Name the enzyme and the school-level lipid products.
  • Interpret a lipid investigation using the stated products and controls.
Core overall model: amylase digests starch to simple reducing sugars; proteases digest protein to amino acids; lipase digests fats/oils to fatty acids and glycerol. Individual detailed steps can include intermediate products.Keep each digestive enzymewith its substrateAmylaseStarch → simple reducingsugarsProteases: overall pathwayProtein → amino acidsLipase: overall modelFats/oils → fatty acids +glycerol
Core overall model: amylase digests starch to simple reducing sugars; proteases digest protein to amino acids; lipase digests fats/oils to fatty acids and glycerol. Individual detailed steps can include intermediate products.

Use the required overall model

Lipase catalyses digestion of fats and oils into fatty acids and glycerol in the syllabus’s overall model. Lipid substrate, enzyme and products have different roles. Bile is not a substitute enzyme for this chemical breakdown.

Detailed human digestion includes intermediate lipid products, but the required school account names fatty acids and glycerol. The model is an overall summary rather than a claim that every molecule follows one single step.

Keep physical and chemical roles apart

Emulsification makes smaller lipid droplets, exposing more surface. Lipase changes lipid molecules chemically. Smaller droplets with unchanged molecules are not already the final digestion products.

In supplied investigations, compare the same starting lipid quantity and suitable controlled pH, temperature and enzyme conditions. A colour or pH change needs an explained link to the test method rather than being called automatic proof of complete digestion.

Sources for this lesson

Pause and explain

Which products fit the syllabus lipid model?

Put the idea to work

Worked example

A table lists lipid droplets, lipase and fatty acids/glycerol. Classify the roles.

Show the worked solution
  1. Lipid: substrate.
  2. Lipase: enzyme.
  3. Fatty acids/glycerol: overall products.

Answer Fats/oils are substrate; lipase is enzyme; fatty acids and glycerol are the named overall products.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Complete the lipid digestion relationship with enzyme and products.

Give me a hint

Keep bile separate.

Compare my reasoning
  1. Fats/oils as substrate.
  2. Lipase as enzyme.
  3. Fatty acids and glycerol as products.

Lipase digests fats/oils to fatty acids and glycerol in the overall school model.

Look for these in your work

  • Correct enzyme.
  • Both products.
2 · Independent

Why does a picture of many small oil droplets not prove lipase has acted?

Give me a hint

Droplet subdivision can be physical.

Compare my reasoning
  1. Bile can emulsify droplets.
  2. Chemical-product evidence is separate.

Small droplets can result from emulsification without chemical lipid digestion.

Look for these in your work

  • Physical/chemical distinction.
  • Evidence limit.
3 · Transfer

In a matched investigation, the active-lipase treatment develops fatty-acid products while a no-active-enzyme control does not. What supports the interpretation?

Give me a hint

Use the control and measured product.

Compare my reasoning
  1. Product formation differs with active lipase.
  2. Other conditions are matched.

The controlled product difference supports lipase-catalysed chemical digestion of lipids.

Look for these in your work

  • Control reasoning.
  • No claim of automatic complete digestion.

Common mistakes

  • Bile is not lipase.
  • A small droplet is not a small digestion-product molecule.
Recall without your notes

What can you explain now?

Which products fit the syllabus lipid model?

Compare with the explanation

Fatty acids and glycerol.

These are the required overall products.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Name lipase and its overall products, then contrast that with emulsification.

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Sciences — Co-ordinated (9-1)

Course scope and assessment

This 9–1 pathway maps all 152 detailed subject-content sections in the published 0973 syllabus for exams in 2028 and 2029. The course map follows the same 2028–2029 section codes as Cambridge's A*–G 0654 syllabus, while keeping 0973's grading and entry rules separate. It adapts lessons from the related single-science courses and excludes clear single-science-only topics. A 0973-specific objective-by-objective review, Core/Supplement audit, human subject-teacher review, supervised laboratory experience and cumulative assessment remain in progress. Written practice is self-checked and does not predict an official grade. The separate 2025–2027 syllabus has not been reconciled here. Cambridge lists 0973 only in a limited number of administrative zones: June in zone 3 and centres in Oman and the UAE; November in zone 3 only. Confirm entry with your centre.

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