1.1- Monomers & polymer

Question 1

Describe how you would test a piece of food for the presence of lipid (2)

Answer 1

) 1. Dissolve in alcohol, then add water;

2. White emulsion shows presence of lipid.

Question 2

Describe how proteins are digested in the human gut. (4)

Answer 2

1. Hydrolysis of peptide bonds;
2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids.

Question 3

Name the type of reaction that joins monosaccharides together. (1)

Answer 3

condensation

Question 4

Some cells lining the bronchi of the lungs secrete large amounts of mucus.
Mucus contains protein.
Name one organelle that you would expect to find in large numbers in a
mucus-secreting cell and describe its role in the production of mucus. (2)

Answer 4

Organelle named; Function in protein production / secretion;
Function must be for organelle named
Incorrect organelle = 0
eg
1. Golgi (apparatus);
1. Accept smooth endoplasmic reticulum
2. Package / process proteins;
OR
3. Rough endoplasmic reticulum / ribosomes;
3. Accept alternative correct functions of rough endoplasmic
reticulum. ER / RER is insufficient
3. Accept folding polypeptide / protein
4. Make polypeptide / protein / forming peptide bonds;

Question 5

Describe the structure of proteins. (5)

Answer 5

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;
   Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic /
   disulfide bonds;
7. Quaternary structure is two or more polypeptide chains.

Question 6

Messenger RNA (mRNA) is used during translation to form polypeptides.
Describe how mRNA is produced in the nucleus of a cell. (6)

Answer 6

1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns.

Question 7

Name the type of bond between A (glycerol ) and fatty acid X.

Answer 7

Ester

Question 8

Which of the fatty acids, X or Y, in the figure above is unsaturated? Explain your
answer. (1)

Answer 8

Y (no mark)

Contains double bond between (adjacent) carbon atoms in hydrocarbon chain.