proteins

Question 1

what is the structure of amino acids

Answer 1

carboxylase group - coo-
amino group - nh2
H
R group

Question 2

what is the structure of a protein

Answer 2

Primary structure: sequence of amino acid residues in a polypeptide
chain (N terminus to C terminus)

Secondary structure: local structures of the polypeptide chain,
e.g. alpha helix, beta sheet (hydrogen bonds)

Tertiary structure: due to the bending and twisting of the secondary
structure into a more compact shape (disulphide bonds, ionic bonds,
hydrogen bonds)

Quaternary structure: the combination of a number or different
polypeptide chains and/or associated non-protein groups

Question 3

what are the properties of alpha helix?

Answer 3

• right handed: 3.6 amino acid residues per turn
• formed by the backbone of the protein chain, side-chains extend
  outwards
• formed and stabilised by hydrogen bonds: the oxygen of the
  CO group is hydrogen bonded to the hydrogen of the NH group
  that is situated 4 residues further towards the C terminus of
  the sequence

Question 4

what are the properties of beta pleated sheet

Answer 4

sheet-like structure
- also formed by the backbone of the protein chain, side-chains
extend above and below the sheet
- formed and stabilised by hydrogen bonds: oxygen of the
CO group is hydrogen bonded to the hydrogen of NH group in
different polypeptide chains or in the same chain further away
- adjacent chains can run in the same direction: parallel  sheet or
in opposite direction: antiparallel beta sheet

Question 5

what are examples of globular fibrous proteins

Answer 5

Myoglobin,  Haemoglobin, Cytochrome c, Insulin, 
most enzymes (e.g. Lysozyme)

Fibrous proteins: Collagen, Elastin, alpha keratin

Proteins that form filaments or tubes:
Actin, Tubulin