primary structure
sequence of amino acids
primary structure bonds
covalent bonds (peptide links)
secondary structures
alpha-Helix and beta plated sheets
secondary structure bonding
hydrogen bonding between N-H group in one peptide link and C=O group in another peptide link elsewhere in the polypeptide chain
tertiary structure
overall 3D structure
is a mess
tertiary structure bonding and interactions
- dispersion
- dipole-dipole
- H-bonding
- ionic interactions
- ion-dipole interaction
- disulfide bridge
dispersion
tertiary structure
b/w any R group (particulary non-polar)
dipole-dipole
tertiary structure
b/w partial negatve on one R group and partial positive on another R group
H-bonding
tertiary structure
b/w partial positive of H of O-H or N-H of one R group and partial negative of O or N on another R group
ionic interactions
tertiary structure
b/w cationic (+) R group and anionic (-) R group
ion-dipole interactions
tertiary structure
b/w cationic (+) or anionic (-) R group and partial positive or partial negative on another R group
disulfide bridge
b/w cysteine (cys) redidues of polypeptide chains
quaternary structure
several associated polypeptide chains
still a mess
quaternary structure bonding
- dispersion
- dipole-dipole interaction
- H-bonding
- ionic interactions
NOT disulfide bridge
acid-base property of amino acids
in solution amino F.G acts as a base and carboxy F.G acts as an acid
all amino acids are amphriprotic (act as acid or base)
amino acids in base
pH > 7
carboxy (COOH) loses H+ ion and becomes anionic (-) and is therefore a conjugate base
amino acids in acids
pH < 7
amino (NH) gains a H+ ion and becomes cationic (+) and is therefore a conjugate acid
amino acids in H2O
neutral (pH = 7)
amino (NH) gains a H+ and carboxy (COOH) loses a H+ therefore not changing the NET charge of the amino acid.
still has a neutral change and is a zwitterion
zwitterion
exchange of H+ ion within the molecule
when an amino acid forms zwitterion at a specific pH that is the neutral pH for that particular amino acid
eg. pH (zwitterion) = x = neutral pH
doesnt have to be 7 at neutral pH
