Unit 1

Question 1

What is hydrolysis?

Answer 1

1. Breaks a chemical bonds between two molecules
2. Using water

Question 2

What is a condensation reaction?

Answer 2

1. Creates a chemical bond
2. Removes a molecule of water

Question 3

Glycogen Structure (3)

Answer 3

1. Polysaccharide of a-glucose
2. (Joined by) Glycosidic bonds
3. Branched Structure

Question 4

Glycogen compared with cellulose (4)

Answer 4

1. Cellulose is made up of B-glucose and glycogen is made up of a-glucose.
2. Cellulose molecule has straight chain and glycogen is branched
3. Cellulose molecule has straight chain and glycogen is coiled
4. Glycogen has 1,4 and 1,6 glycosidic bonds and cellulose has only 1,4 glycosidic bonds.

Question 5

Glycogen structure related to function (5)

Answer 5

1. Insoluble, so so doesn’t affect water potential
2. Branched, so makes molecule compact
3. Polymer of (a)glucose so provides glucose for respiration
4. Branched for fast breakdown / enzyme action
5. Large, so can’t cross the cell membrane.

Question 6

3 properties of starch that relate to its function (6)

Answer 6

1. Insoluble
2. So doesn’t affect water potential
3. Helical
4. So compact
5. Large Molecule
6. So cannot leave cell

Question 7

Test for reducing sugar

Answer 7

1. Heat with Benedict’s Reagent
2. Colour Change from blue to brick-red

Question 8

Test for a Non-Reducing Sugar

Answer 8

1. Heat with Benedict’s reagent and no colour change
2. Boil with acid (HCL) and then neutralise with (NaHCO3)
3. Re-react with Benedict’s’ and colour change from blue to brick-red

Question 9

Test for Starch

Answer 9

1. Add iodine in potassium iodine solution
2. Colour Change from brown to blue-black

Question 10

How are triglycerides formed?

Answer 10

1. One glycerol and three fatty acids
2. Condensation and removal of three molecules of water
3. Ester bonds are then formed

Question 11

Structure of Phospholipids compared with Triglycerides (8)

Answer 11

1. Both contain ester bonds
2. Both contain glycerol
3. Fatty acids on both may be saturated or unsaturated
4. Both are insoluble in water
5. Both contain C, H and O but phospholipids also contain P
6. Triglyceride has 3 fatty acids and phospholipid has two fatty acids plus phosphate group.
7. Triglycerides are non-polar and phospholipids are polar with polar regions
8. Phospholipids form monolayer but triglycerides don’t

Question 12

Describe how an ester bond is formed in a phospholipid molecule.

Answer 12

1. Condensation reaction
2. Between glycerol and fatty acid

Question 13

Test for a lipid

Answer 13

1. Add ethanol, then mix with water
2. White / milky emulsion

Question 14

Uses and properties of ATP as an energy source (5)

Answer 14

1. Releases relatively small amount of energy
2. Releases energy instantaneously
3. Phosphorylates other compounds making them more reactive
4. Can be rapidly re-synthesised
5. Does not leave cells

Question 15

Structure of ATP compared with DNA (3)

Answer 15

1. ATP has ribose and DNA has deoxyribose
2. ATP has 3 phosphates and DNA nucleotide has one phosphate
3. Base is always adenine in ATP and bases vary in DNA nucleotide

Question 16

Properties that make water important for organisms (6)

Answer 16

1. A metabolite in condensation/hydrolysis reactions
2. A solvent, so metabolic reactions can occur
3. High 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 xylem
6. Cohesion between water molecules so provides surface tension for supporting smaller organisms