2.4

Question 1

SKILL: Drawing molecular diagrams to show the formation of a peptide bond

Answer 1

…

Question 2

How are amino acids linked?

Answer 2

They are linked together by condensation reactions to form polypeptides

Question 3

How many different amino acids are there in living things?

Answer 3

20, they were produced by chemical processes before origin of life, therefore all organisms have used then & continue to.

There are exceptions: some species of ARCHAEA use non-standard amino acids

Question 4

Explain why such a large variety of polypeptides can be formed:

Answer 4

There are 20 amino acids which can be joined together in any order and in any number

Question 5

How is the amino acid sequence of polypeptides coded for?

Answer 5

THE ORDER OF BASES IN THE DNA OF A GENE CODES FOR THE ORDER OF AMINO ACIDS IN A POLYPEPTIDE CHAIN, WHERE 3 BASES CODE FOR 1 AMINO ACID)

Question 6

A protein may consist of a single polypeptide or more than one polypeptide linked together, name some examples and their functions

Answer 6

Lysozyme:
1 polypeptide, kills bacteria by digesting the peptidoglycan in their cell walls

Integrin:
2 polypeptides, used to make connection b/w structures inside & outside the cell

Collagen:
3 polypeptides, has high tensile strength (stretch resistant)

Haemoglobin:
4 polypeptides, binds to O2 in lungs & transports it around the body to be released in respiring tissues

Question 7

What determines the three-dimensional conformation of a protein? Compare fibrous & globular proteins:

Answer 7

The sequence of amino acids

Fibrous-Collagen
-3 polypeptide chains
-each chain coiled into helix
-3 helices are wrapped around each other, forming triple helix
-held together by H-bonds
-insoluble
is a structural protein w/ high tensile strength

Globular-Insulin
-stored as hexamer
-consists of 2 polypeptide chains, which are coiled & folded into compact, spherical shape
-soluble
is a hormone produced by the pancreas

Question 8

What can protein denaturation be caused by?

Answer 8

Excessive heat: so much kinetic energy that atoms vibrate violently enough to overcome forces of attraction b/w R-groups

Extremes of pH: interfere w/ charges on R-groups, breaking electrostatic forces of attraction

Question 9

Name protein & protein functions:

Answer 9

Catalysis: thousands of different enzymes catalyse specific chemical reactions, e.g. rubisco
Hormones: chemically diverse, e.g. insulin (regulates blood glucose lvl)
Receptors: For hormones, neurotransmitters, taste, smells, light e.g. rhodopsin
Immunity: can make a huge number of antibodies, e.g. immunoglobulins
Habitat: organisms can use proteins to build themselves a habitat, e.g. spider silk