Monomers And Polymers - Mark Scheme Answers (study Mind)

Question 1

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

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

Answer 1

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 2

Describe the protein structure (5)

Answer 2

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 /
   disulfide bonds;
7. Quaternary structure is two or more polypeptide chains.

Question 3

Describe how proteins are digested in human gut (4)

Answer 3

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 4

Explain the difference in the structure of starter molecule and cellulose molecule molecule show in diagram above

Answer 4

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 5

Explain one way in which starch molecules are adapted for their function in plant cells.

Answer 5

1) insoluble
2) don’t affect water potential

Question 6

Explain how cellulose molecules are adapted for their function in plant cells. (2)

Answer 6

1. Long and straight chains
2. Become linked together by many hydrogen bonds to form fibrils
3. Provide strength to cell walls of plants

Question 7

Why is there no cholesterol in cell surface membrane?

Answer 7

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

Question 8

(c) Describe the chemical reactions involved in the conversion of polymers to
monomers and monomers to polymers.

Give two named examples of polymers and their associated monomers to
illustrate your answer.

Answer 8

1. A condensation reaction joins monomers together and forms a
   (chemical) bond and releases water;
2. A hydrolysis reaction breaks a (chemical) bond between
   monomers and uses water;
3. nucleotide and polynucleotide (DNA or RNA), Alpha glucose and starch/glycogen, Beta glucose and cellulose.
4. A second suitable example of polymers and the monomers
   from which they are made;
5. Reference to a correct bond within a named polymer;

Question 9

What is a monomer?

Answer 9

Small unit/ molecule from which larger molecules are made