Proteins

Question 1

primary structure

Answer 1

The sequence of amino acids held together by peptide bonds.
This determines the secondary structure and tertiary structure (3D shape)

Question 2

Secondary structure

Answer 2

folding of primary structure-the polypeptide chain coils to form an alpha helix or folds to form beta pleated sheet
held together by weak HB

Question 3

Tertiary structure

Answer 3

further folding of polypeptide chain to give a more complex 3-D shape and is closely related to the function of a particular protein

•Hydrogen bonds-weak bonds between the R groups easily broken by temp/change in pH

•ionic bonds-between +/- charged R groups of amino acids, stronger than HB + broken by change in pH

•disulphide bonds-strong covalent bonds between sulphurs in R group of amino acid cysteine

•hydrophobic interactions -between non-polar R groups which tend to cluster together towards the centre of the molecule
hydrophobic-centre
hydrophilic-outside

Question 4

quarternary structure

Answer 4

made up of more than one polypeptide chain.

E.G.haemoglobin haemoglobin consists of 4 polypeptide chains.
Each chain has a heam group which contains Fe2+ ion
haemoglobins function is to carry oxygen from the lungs to respiring tissues.

Question 5

fibrous proteins

Answer 5

•Form long fibres
•regular+ repetitive sequence of amino acids
•insoluble in water
•structural roles (collagen)

Question 6

globular proteins

Answer 6

•Fold up into a compact ball shape
•wide range of amino acid sequence in the structure
•more water soluble than fibrous proteins
•metabolic role in living organisms(antibodies, enzymes)