Unit 3: Section 8 - amino acids, proteins and DNA MDY * Flashcards
amino acids proteins and enzymes DNA
what do amino acids consist of?
it has a basic amino acid group (NH2) and an acidic carboxyl group (COOH)
it is also attached to an H and an R group
what properties do amino acids have?
amphoteric - both basic and acidic properties
chiral - rotate plane polarised light (except glycine, who’s R group is just H)
what is a zwitterion?
a dipolar ion - it has a positive and a negative charge
RNH3+ and COO-
only exist near an amino acids isoelectric point
what is an amino acids isoelectric point?
the pH where the average overall charge on the amino acid is zero
how to identify the amino acids in a mixture?
thin-layer chromatography
what are proteins?
they are made up of lots of amino acids joined together by peptide links
joined via condensation between NH2 and COOH
how can proteins be broken down?
via hydrolysis
hot aqueous 6M hydrochloric acid and heat under reflux for 24 hours
what are the structures of a protein?
primary
secondary
tertiary
quarternary
what is the primary structure of a protein?
the primary structure is the sequence of amino acids in the long chain the makes up the protein
what is the secondary structure of a protein?
the peptide links can form hydrogen bonds (between C=O and NH) with each other
to form an alpha helix or beta-pleated sheet
what is the tertiary structure of a protein?
chain of amino acids coiled and folded
extra bonds form to make 3D shape
held together by various bonds between R groups of amino acids
what are types of bonds are there that hold proteins in shape in the tertiary structure?
hydrogen bonds
disulfide bonds
covalent bonds
ionic bonds
what do hydrogen bonds do in proteins?
they exist between polar groups
e.g. OH and NH2
they stabilise both secondary and tertiary structure
what do disulfide bonds do in prteins?
amino acid, cysteins, contains a thiol group (SH)
thiol groups can lose their Hs and join together to form a sulfur-sulfur bond
what factors affect hydrogen and disulfide bonds?
temperature
pH
how do enzymes speed up reactions?
biological catalysts
catalyse every metabolic reaction in the bodies of living organisms
what are enzymes?
proteins, some have non-protein parts
every enzyme has an active site, where substrate fits to interact with enzyme
active site is 3D - part of tertiary structure
how are enzymes specific?
only work with specific substrates
substrate has to fit active site (lock and key model)
active sites are stereospecific
what does it mean that active sites are stereospecific?
they’ll only work on 1 enantiomer of a substrate. the other enantiomer won’t fit properly in the active site, so the enzyme can’t work on it
what are inhibitors?
molecules that have a similar shape to the substrate
they compete with the substrate to bond to the active site, but no reaction follows. they block active site so no substrate can fit
what does the amount of inhibition depend on?
the relative concentrations of inhibitor and substrate
how strongly the inhibitor bonds to the active site
how do antibiotics kill bacteria?
they block the active site of an enzyme in bacteria that helps to make their cell wall, causing them to weaken over time, so bacteria eventually burst
why is it difficult to find a drug that works as an enzyme inhibitor?
active site is very specific
if drug is chiral only 1 enantiomer works
how are new drug molecules found?
trial and error
then adapt any that work to try and improve them, this takes a long time
