what shape is water
tetrahedral
hydrophilic
dissolves in water
how do hydrophilic molecules dissolve in hydrophilic substances
electrostatic interactions - ion-dipole, dipole-dipole interactions
hydrogen bond
covalent bond between a hydrogen atom and a more electronegative one creating a polarised bond
what is the strength of a hydrogen bond compared to covalent
- individually weaker
- collectively strong
hydrophobic
non-polar substances are insoluble in water
what is the hydrophobic effect
2 layers form when polar and non-polar substances are mixed
ampipathic
molecules with both hydrophilic and hydrophobic parts
describe an ampipathic molecule
polar ‘head’, hydrophobic ‘tail’
what do ampipathic molecules form in water
micelles
what if the function of the proteins in the phospholipid bilayer
- confer selectivity
- involved inrecognition
what are amino acids made of
proteins and polypeptides
in an amino acid what is bonded to the central carbon atom
- amide group
- R group
- carboxyl group
- hydrogen
steroisomer
non-superimposable mirror images
what are the 4 types of amino acids
- polar (uncharged)
- non-polar (uncharged)
- acidic
- basic
describe peptide bond formation
- the carboxyl and amino group of 2 amino acids bond via peptidyl transferase
- this forms an amide group
what direction does peptide bond formation occur in
towards the C terminal
what is a peptide bond
partial double bond character electrons, form the N and C terminal but arent covanlently bonded
describe peptide bonds
planar, strong and rigid
acid
substance that donates a proton
base
proton acceptor
what does the strength of an acid depend on
how readily it donates a proton
what equation is used to measure an acids strength
dissociation constant
Ka= [H+][A-]/[HA]
what is pH a measurement of
the amount of protons in a solution
what is the equation for measuring pH
pH = -log10[H+]
what is the equation to measure an acids strength with pKa
pKa = -log1o[Ka]
how do you work out the log of a pH to use in an equation
the log of no.x to its base n is the no. of times n has to be multiplied with itself to get x
log10^100 = log 10^10^2 - pH7 = 10^-7
what equation is used to connect the pKa of a weak acid with the pH of its solution
Henderson Hasselbach
what is the Henderson Hasselbalch used to calculate
properties of a buffer solution
what is the Henderson Hasselbalch equation
pKa - pH = log10[HA]/[A]
buffer
solution that controls the pH of a reaction mixture by resisting a change in pH with moderate amounts of acid or base added at their pKa value
when [acid] = [conjugate base] what else is equal
pH = pKa
describe a titration curve
the graph shows that at the buffers pKa value it resists a change in pH
what are zwitterions
amino acids without a charged side group in a neutral solution, no net charge
contain 2 titratable groups
isoelectric pH
pH at which a molecule has no net charge
zwitterions with 2 titratable groups means what in terms of pKa
2 pKa values
proteins can act in a different way as pH varies
what part of proteins can be ionised
the ends
what can a change in pH do to the ionisation of a proetin
change the ionisation and therfore structure and function
