amino acids and proteins Flashcards
structure of aa
H amine group carboxyl group Rgroup chiral C
what is an acid
proton donor
base
proton acceptor
isoelectric point
pH at which net charge is ), molecule would not migrate in an electric point
peptide bond
rigid
planar
strong covalent bond
only broken down by proteases
what can differ in in the R side chain
size shape charge H bonding chemical reactivity
classifications of amino acids/side chains
polar
non polar
acidic
basic
polar aa
uneven charge distribution
forms H bonds, therefore hydrophilic
e.g. serine
non polar aa
equal charge distribution hydrophobic tend to be on the inside of protein some aromatic e.g. glycine
acidic aa
have a - charge at neural pH
contain extra carboxyl group
e.g. aspartate
basic aa
+ charge at neutral pH
contain amino group
e.g. lysine
method used to separate proteins or aa
electrophoresis polyacrimide porous gel protiens coated in - charge move towards anode separate by size
2d electrophoresis
run in gradient of pH
move until isoelectric point is reached
i.e. measure size and isoelectric point
post translational modification
lipid addition oxidation/carboxylation/acetylation cleavage glycosylation (for tagging) phosphorylation (alters intracellular signalling on/off)
aa in disease
sickle cell anaemia - single point mutation in haemoglobin structure
how can pH determine charge on aa
carboxyl and amine group ionisable
low pH - amine group protonated, carboyxl no charge
neutral pH- zwitter ion formed (no overall charge) ISOELECTRIC POINT
high pH - carboxyl group charged
