1.4.1 general properties of proteins Flashcards
1
Q
describe the general structure of an amino acid
A
- COOH = carboxyl group
- R = variable group
- H2N = amine group
2
Q
how many amino acids are common in all organisms and how do they vary
A
the 20 amino acids that are common in all organisms differ only in their side group ( R )
3
Q
describe how amino acids join together
A
- condensation reaction
- removing a water molecule
- between carboxyl group of one and amine group of another
- forming a peptide bond
4
Q
what are dipeptides
A
2 amino acids joined together
5
Q
what are polypeptides
A
many amino acids joined together - a functional protein may contain one or more polypeptides
6
Q
describe the primary structure of a protein
A
the sequence of amino acids in a polypeptide chain, joined by peptide bonds
7
Q
describe the secondary structure of a protein
A
- folding of polypeptide either into alpha helix or beta pleated sheets
- due to hydrogen bonding between amino acids
- between NH and C=O groups
8
Q
describe the tertiary structure of a protein
A
- 3D folding of polypeptide chain
- due to interactions between amino acid R groups ( dependent on sequence of amino acids )
- forming hydrogen bonds, ionic bonds and disulphide bridges
9
Q
describe the quaternary structure of a protein
A
- more than one polypeptide chain
- formed by interactions between polypeptides ( hydrogen bonds, ionic bonds and disulphide bridges )
10
Q
describe the test for proteins
A
- add biuret reagent ( sodium hydroxide + copper sulphate )
- positive result = purple/lilac colour ( negative stays blue ) indicating presence of peptide bonds
