3.6 Structure of proteins Flashcards
what do proteins contain
CHO + nitrogen
roles of proteins
- structural
- catalytic
- signalling
- immunological
types of amino acids and how they are obtained
essential amino acids = through diet
non-essential amino acids = made by body
how are proteins synthesised
hydroxyl group of one amino acid interacts with hydrogen in amine group of another to form H2O and a peptide bond
importance of R-group in amino acids
- gives them the ability to interact with other amino acids
- results in complex structures as they fold in different ways
primary structure
PEPTIDE BONDS
sequence in which amino acids join
directed by information in DNA
determines folding and therefore function
secondary structure
HYDROGEN BONDS
alpha helix
beta pleated sheets
tertiary structure
- folding into its final shape
- coiling / folding brings R-groups close enough to interact so further folding occurs
interactions in tertiary structure (4)
- hydrophobic/hydrophilic interactions
- hydrogen bonds
- ionic bonds
- disulfide bonds
quaternary structure
results from association of 2 or more individual proteins
e.g. haemoglobin
breakdown of peptides
- proteases catalyse reverse reaction to turn peptides into amino acids
- water molecule is used
what is the biuret reagent
mixture of alkali +copper sulfate
test for proteins
biuret test
- mix liquid sample with equal volume of 10% NaOH
- add drops of 1% copper sulfate until blue
- leave for 5 minutes
peptide bonds = form violet complexes
thin layer chromatography
stationary phase = thin layer of silica gel
mobile phase = organic solvent
mobile phase picks up amino acids and moves them through stationary phase which separates them
how do you calculate Rf value
Rf = distance travelled by component / distance travelled by solvent
