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2.2 Animal tissues, organs and organ systems

2.2 Animal tissues, organs and organ systems

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Question 27

Lipase is an enzyme that digests lipids (fats and oils) in the human body.

a.

Lipase is a biological polymer. Name the monomer (smaller molecule) that forms this polymer.

[1]
b.

Name two organs in the human digestive system that produce lipase.

[2]
c.

Explain how lipase breaks down lipids. Answer in terms of the 'lock and key theory'.

[3]
d.

A student investigated the effect of pH on the activity of lipase.

The student used the following method:

  1. Measure 5 cm35\text{ cm}^35 cm3 of milk, 1 cm31\text{ cm}^31 cm3 of sodium carbonate solution (to make the solution alkaline), and 1 cm31\text{ cm}^31 cm3 of phenolphthalein indicator into a test tube. The solution turns pink.
  2. Place this test tube and a separate tube containing 2 cm32\text{ cm}^32 cm3 of lipase solution into a water bath at 35∘C35^\circ\text{C}35∘C for 5 minutes.
  3. Add the lipase solution to the milk mixture, stir, and start a stopwatch.
  4. Record the time taken for the pink colour to disappear.
  5. Repeat the experiment using buffer solutions of different pH values.

Why did the student leave the tubes in the water bath for 5 minutes before mixing them?

[1]
e.

Name two control variables the student kept constant in this investigation.

[2]
f.

Explain why the pink colour disappears when lipase breaks down the lipids in the milk.

[2]
Markscheme

2.2 Animal tissues, organs and organ systems Questions

  1. GCSE
  2. /Biology
  3. /2.2 Animal tissues, organs and organ systems

44 exam-style questions on AQA GCSE Biology 2.2 Animal tissues, organs and organ systems, covering 2.2.1 The human digestive system, 2.2.2 The heart and blood vessels, 2.2.3 Blood, 2.2.4 Coronary heart disease: a non-communicable disease, 2.2.5 Health issues, 2.2.6 The effect of lifestyle on some non-communicable diseases, and 2.2.7 Cancer. Each one has a worked solution and a mark scheme showing where the marks go.

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