IGCSE & GCSE Biology by D. G. Mackean

Here you will find the answers to the 'in-text' questions which occur in IGCSE Biology (2nd edition) and GCSE Biology (3rd edition) by D. G. Mackean, published by Hodder Education, London, UK.

Chapters: | Index | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 |

Chapter 2. The chemicals of living cells

Page 13

1. Proteins; provide the basic materials (amino acids) for making cytoplasm which forms cells, tissues and organs, and for making enzymes which control all the reactions in the cell.
2. a proteins b carbohydrates and lipids.
3. a carbohydrates; sugar, starch, cellulose
    b salts; iron sulphate, sodium chloride
    c lipids; butter, olive oil.
4. Carbohydrates would need nitrogen. Plants get nitrogen in the form of nitrates in the soil.
5. Synthesis of starch and cellulose from glucose; synthesis of amino acids from glucose and salts; synthesis of glucose from carbon dioxide and water.

Page 18

1. Only d applies to all catalysts.
2. a The rate would increase. Most chemical reactions are speeded up by a rise in temperature.
    b The rate would fall to zero. Temperatures over 50 degrees C denature most enzymes.
3. Yes. Enzymes are essential for all the processes taking place inside a cell.
4. Dipping the apple into boiling water denatures the enzymes responsible for producing the brown discolouration.
5. The enzyme needs to combine briefly with the molecules of the two reactants, glycine and valine. The same enzyme may still combine with the glycine molecule but will not ‘fit’ with the serine molecule.

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Section 1, Chapters 1-5
Section 2, Chapters 6-9
Section 3, Chapters 10-12
Section 3, Chapters 13-17
Section 3, Chapters 18-20
Section 4, Chapters 21-24
Section 5, Chapters 25-27
Section 5, Chapters 28-29
Section 6, Chapters 30-34
Section 6, Chapters 35-37
Section 7, Chapters 38-39
Section 8, Chapters 40-41