Chapter 1: Biological Molecules

Question 1

Describe how the function of glycogen in related to its function [4 marks]

Answer 1

1. helix/coiled/branched so compact
2. polymer of glucose so easily hydrolyzed
3. branched so more ends for faster glycolysis
4. glucose polymer so provides respiratory substrate for energy
5. insoluble so does not affect water potential

Question 2

Describe how the structure of starch and cellulose molecules are related to their functions [5 marks]

Answer 2

starch
1. helical/spiral shape so compact
2. large/insoluble so osmotically inactive
3. branched so glucose is easily released for respiration
large so cannot leave the cell
cellulose
5. long, straight/unbranched chains of beta glucose
6. joined by hydrogen bonding
7. to form fibrils
8. provides rigidity/strength

Question 3

Describe how the structure of a protein depends on the amino acids it contains [5 marks]

Answer 3

1. structure is determined by R group interactions
2. primary structure is sequence of amino acids
3. secondary structure is formed by hydrogen bonding
4. tertiary structure formed by interactions
5. creates active site in enzymes
6. quaternary structure contains more than one polypeptide chain

Question 4

Describe the structure of proteins [5 marks]

Answer 4

1. polymer of amino acids
2. joined by peptide bonds
3. formed by condensation
4. primary structure is order of amino acids
5. secondary structure is folding of polypeptide chain due to hydrogen bonding
6. tertiary structure is 3-D folding due to hydrogen bonding and ionic bonds
7. quaternary structure is two or more polypeptide chains

Question 5

Compare and contrast the structure and properties of triglycerides and phospholipids [5 marks]

Answer 5

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 three fatty acids and phospholipid has two fatty acids plus a phosphate group
7. triglycerides are hydrophobic and phospholipids have a hydrophilic and hydrophobic region
8. phospholipids form monolayer/bilayer but triglycerides don’t

Question 6

Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein [4 marks]

Answer 6

1. glucose and galactose
2. joined by a condensation reaction
3. joined by a glycosidic bond
4. added to polypeptide in the golgi apparatus

Question 7

Explain why maltase
- only breaks down maltose
- allow this reaction to take place at normal body temperature [5 marks]

Answer 7

1. tertiary structure
2. active site is complementary to maltose
3. description of induced fit
4. enzyme is a catalyst
5. by forming enzyme-substrate complex

Question 8

Describe competitive and non-competitive inhibition of an enzyme [5 marks]

Answer 8

1. inhibitors reduce binding of enzyme to substrate
   competitive inhibition
2. inhibitor similar shape to substrate
3. binds to the active site of the enzyme
4. can be overcome by more substrate
   non-competitive inhibition
5. inhibitor binds to site on enzyme other than active site
6. prevents formation of active site
7. cannot be overcome by adding more substrate

Question 9

Describe the biochemical tests you would use to confirm the presence of lipid, non-reducing sugar and amylase in a sample [5 marks]

Answer 9

lipid
1. dissolve in ethanol then add water and shake
2. a milky white emulsion
non-reducing sugar
3. do benedict’s test and stays blue
4. boil with acid then neutralise with alkali
5. heat with benedicts and becomes red/orange
amylase
6. add biuret and becomes purple
7. add starch, test for reducing sugar