1.1 monomers and polymers epqs redos

Question 1

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.

Answer 1

1. Golgi (apparatus);
2. Accept smooth endoplasmic reticulum
3. Package / process proteins;
   OR
4. Rough endoplasmic reticulum / ribosomes;
5. Accept alternative correct functions of rough endoplasmic
   reticulum. ER / RER is insufficient
6. Accept folding polypeptide / protein
7. Make polypeptide / protein / forming peptide bonds;
   OR
8. Mitochondria;
9. Release of energy / make ATP;
10. Reject produce / make energy
11. Accept produce energy in the form of ATP
    OR
12. Vesicles;
13. Secretion / transport of protein;

Question 2

b) In this model of digestion in the human gut, what other enzyme is required for the
complete digestion of starch?
(c) What was the purpose of step 2, in which samples were mixed with water,
hydrochloric acid and pepsin?
(d) In the control experiments, cooked wheat was chopped up to copy the effect of chewing. Suggest a more appropriate control experiment. Explain your suggestion.

Answer 2

a) 1. Maltose;

2. Salivary amylase breaks down starch.
   (b) Maltase.
   (c) (Mimics / reproduces) effect of stomach.
   (d) 1. Add boiled saliva;
3. Everything same as experiment but salivary amylase denatured.

Question 3

(3)

Answer 3

(e) 1. Some starch already digested when chewing / in mouth;
2. Faster digestion of chewed starch;
3. Same amount of digestion without chewing at end.

Question 4

Messenger RNA (mRNA) is used during translation to form polypeptides.

Describe how mRNA is produced in the nucleus of a cell. (6)

Answer 4

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 5

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

Answer 5

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 6

Answer 6

1. Starch formed from α-glucose but cellulose formed from β-glucose;
2. Position of hydrogen and hydroxyl groups on carbon atom 1 inverted.

Question 7

(c) Explain how cellulose molecules are adapted for their function in plant cells. (3)

Answer 7

1. Long and straight chains;
2. Become linked together by many hydrogen bonds to form fibrils;
3. Provide strength (to cell wall).

Question 8

(c) Name the type of bond between A and fatty acid X.
(d) Which of the fatty acids, X or Y, in the figure above is unsaturated? Explain your
answer.

Answer 8

(b) glycerol
(c) ester
(d) Y (no mark)
Contains double bond between (adjacent) carbon atoms in hydrocarbon chain.

Question 9

Answer 9

1. Divide mass of each lipid by total mass of all lipids (in that type of cell);
2. Multiply answer by 100.

Question 10

Cholesterol increases the stability of plasma membranes. Cholesterol does this by
making membranes less flexible. Suggest one advantage of the different percentage of cholesterol in red blood cells
compared with cells lining the ileum.

Answer 10

Red blood cells free in blood / not supported by other cells so cholesterol helps to maintain shape;

Question 11

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why. (2)

Answer 11

1. Cell unable to change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid / made of peptidoglycan / murein.

Question 12

What is a monomer?

Answer 12

(a monomer is a smaller / repeating) unit / molecule from which larger
molecules / polymers are made;