Proteins and enzymes 2016-2021)

Question 1

what type of enzyme will hydrolyse peptide bond in the polymer

Answer 1

endopeptidases

Question 2

Give the number of different R groups in the polypeptide

Answer 2

each r group for each triplet of bases ( 12 amino acids= 4 r groups)

Question 3

Describe the induced-fit model of enzyme action and how an enzyme acts
as a catalyst.

Answer 3

1. Substrate binds to the active site/enzyme
   Active site changes shape (slightly) so it is complementary to
   substrate
2. Reduces activation energy;

Question 4

Describe how the structure of a protein depends on the amino acids it
contains.

Answer 4

Structure is determined by (relative) position of amino acid/R group/interactions;
Primary structure is sequence/order of amino acids;
Secondary structure formed by hydrogen bonding (between amino
acids);
Tertiary structure formed by interactions (between R groups);

Question 5

Describe how amino acids join to form a polypeptide so there is always
NH2 at one end and COOH at the other end.

Answer 5

amine group joins to a carboxyl so there is a free amine group and carboxyl group at the other end

Question 6

Describe two ways in which all dipeptides are similar and one way in
which they might differ.

Answer 6

• different R groups and have amine and carboxyl group at each end
• all have peptide bonds

Question 7

Describe how a non-competitive inhibitor can reduce the rate of an
enzyme-controlled reaction.

Answer 7

• bind to allosteric site
• change tertiary structure
• no longer complimentary

Question 8

Describe how a peptide bond is formed between two amino acids to form a
dipeptide.

Answer 8

• condensation reaction releases water between amine group and carboxyl group forming peptide bond

Question 9

Two proteins have the same number and type of amino acids but different
tertiary structures.
Explain why.

Answer 9

Different sequence of amino acids
Forms ionic / hydrogen / disulfide bonds in different places;