Topic 1 - Biological molecules ms

Question 1

Describe how an ATP molecule is formed from its component molecules

Answer 1

1. A condensation reaction
2. Between adenine, ribose and 3 phosphates
3. ATP synthase

Question 2

Give 2 ways in which ATP is a suitable energy source for cells to use

Answer 2

1. Phosphorylates other compounds making them more reactive
2. Releases energy instantaneously
3. Is nor lost
4. Rapidly re-synthesised
5. Releases small manageable amounts of energy

Question 3

Describe how ATP is resynthesised in cells

Answer 3

1. From ADP and Pi
2. ATP synthase
3. In respiration/photosynthesis

Question 4

Give 2 ways in which the hydrolysis of ATP is used in cells

Answer 4

1. Provides energy for active transport
2. Phosphorylates other compounds making them more reactive

Question 5

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

Answer 5

1. High specific heat capacity
2. Requires lots of energy to change temperature

Question 6

Give 2 properties of water that are important in the cytoplasm+ explain

Answer 6

1. Polar- acts as a universal solvent
2. (Universal) solvent - makes reactions faster in solutions

Question 7

State and explain the property of water that helps to prevent an increase in temp in the cell

Answer 7

1. High specific heat capacity
2. Buffers changes in temperature

Question 8

Explain 5 properties that make water important for organisms

Answer 8

1. Metabolite in condensation/hydrolysis reactions
   2.High specific heat capacity- buffers changes in temp
2. High latent heat of vaporisation- provides a cooling effect
3. Cohesion (between water molecules) - creates surface tension, supporting small organisms
4. Cohesion (between water molecules) - supports columns of water

Question 9

Describe how a triglyercide molecule is formed

Answer 9

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

Question 10

Describe how a phospholipid molecule is formed

Answer 10

1. Condensation
2. Between glycerol and fatty acid

Question 11

Describe how you test for the presence of a lipid

Answer 11

1. Crush/grind
2. Add ethanol/alcohol and shake
3. Add water and shake
4. A cloudy white emulsion will form

Question 13

What is a monomer?

Answer 13

A smaller/repeating unit from which larger molecules/polymers are made

Question 14

Contrast the structure of glycogen and cellulose

Answer 14

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 only has 1,4 glycosidic bonds

Question 15

Describe the biochemical test to show that raffinose solution contains a non-reducing sugar

Answer 15

Heat with acid and neutralise
Heat with Benedict’s (solution)
Red precipitate/colour

Question 16

Describe and explain two features of starch that make it a good storage molecule

Answer 16

Insoluble so doesn’t affect water potential
Branched/coiled/helix so makes a molecule compact
Polymer of (a) glucose so provides glucose for respiration
Branched ends for fast breakdown
Large molecule so can’t cross the cell membrane

Question 17

Define isomer

Answer 17

Same molecular formula but different structural formula

Question 18

2 similarities between starch and glycogen

Answer 18

Both polysaccharides and contain glyosidic bonds

Question 19

2 differences between starch and glycogen

Answer 19

Glycogen is more highly branched
Starch is made up of amylose and amylopectin whereas glycogen is made up of one molecule

Question 20

Describe how the structure of DNA relates to its function. (6)

Answer 20

Sugar-phosphate (backbone)/double stranded/helix so provides strength/stability /protects bases/protects hydrogen bonds;
Long/large molecule so can store lots of information;
Helix/coiled so compact;
Base sequence allows information to be stored/ base sequence codes for amino acids/protein;
Double stranded so replication can occur semi-conservatively/ strands can act as templates;
Complementary base pairing / A-T and G-C so accurate replication/identical copies can be made;
(Weak) hydrogen bonds for replication/ unzipping/strand separation;
Many weak hydrogen bonds so stable/strong molecule;

Question 21

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

Answer 21

1. made from β-glucose;
2. joined by condensation / removing molecule of water / glycosidic bond;
3. 1 : 4 link specified or described;
4. “flipping over” of alternate molecules;
5. hydrogen bonds linking chains / long straight chains;
6. cellulose makes cell walls strong / cellulose fibres are strong;
7. can resist turgor pressure / osmotic pressure / pulling forces;
8. bond difficult to break;
9. resists digestion / action of microorganisms / enzymes;