Water - Mark Scheme Answers (study Mind )

Question 1

Give one way in which the structure of a hemicellulose molecule is similar to

the structure of a cellulose molecule.

Answer 1

both are polymers / polysaccharides / built up from many sugar units / both
contain glycosidic bonds / contain (C)arbon, (H)ydrogen and (O)xygen;

Question 2

two ways in which the structure of a hemicellulose
molecule differs from the structure of a cellulose molecule.

Answer 2

• hemicellulose shorter / smaller than cellulose / fewer carbons;
• hemicellulose from pentose / five-carbon sugars and cellulose from
  hexose / glucose / six-carbon sugars;

Question 3

Describe the structure of a cellulose molecule and explain how cellulose is adapted
for its function in cells.

Answer 3

• made from β-glucose; joined by condensation / removing molecule of water / glycosidic bond; 1 : 4 link specified or described;

1. hydrogen bonds linking chains / long straight chains;
2. cellulose makes cell walls strong / cellulose fibres are strong;
3. can resist turgor pressure / osmotic pressure / pulling forces;
4. bond difficult to break;
5. resists digestion / action of microorganisms / enzymes;

Question 4

The movement of the woodlice in low relative humidity is an advantage to their survival.
Explain how.

Answer 4

Low humidity results in more woodlice moving

So increased movement increased chance of leaving dry / unfavourable
environment so reduce water loss / reduce evaporation

Question 5

Explain five properties that make water important for organisms. (5)

Answer 5

1. A metabolite in condensation/hydrolysis photosynthesis/respiration;
2. A solvent so (metabolic) reactions can occur
3. High (specific) heat capacity so buffers changes in temperature;
4. Large latent heat of vaporisation so provides a cooling effect (through evaporation);
5. Cohesion (between water molecules) so supports columns of water (in plants);
6. Cohesion (between water molecules) so produces surface tension supporting (small) organisms;

Question 6

State and explain the property of water that helps to prevent temperature increase in a cell.

Answer 6

1. High (specific) heat capacity;
2. Buffers changes in temperature;

Question 7

State and explain the property of water that can help to buffer changes in temperature.

Answer 7

1. (water has a relatively) high (specific) heat capacity;
2. Can gain / lose a lot of heat / energy without changing temperature;

Question 8

Give two properties of water that are important in the cytoplasm of cells.
For each property of water, explain its importance in the cytoplasm.

Answer 8

1. Polar molecule; Acts as a (universal) solvent
2. (Universal) solvent; (Metabolic) reactions occur faster in solution
3. Reactive; Takes place in hydrolysis / condensation / named reaction;