Amino acids Flashcards
How do side chain acidic/basic groups affect overall charge on protein?
When the side chains get protonated/deprotonated, the charge is affected.
Why is tyrosine nonpolar?
Due to the 4 carbon rule, molecules should have a polar group every 4 carbons.
Tyrosine only has 1 polar group for seven nonpolar carbons. This is NOT enough to make the molecule polar, not enough polar groups in side chain to account for nonpolar carbons
Amino Acid side chains are used in chemical interactions like…
salt bridges.
Salt bridge = hydrogen bonding and electrostatic interaction
Dispersion force
weakest intermolecular force, temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles
characteristics of amino acidds
optically active, asymmetrical and non-superimposable (chiral)
L-amino acids and D-sugars
L and D rotate light differently… most highly oxidized carbon at the top, NH3+ on left = L-amino acid.
How do we deal with ambiguity between whether something is L or D when there is more than 1 stereocenter
Assign priority groups:
R: if priority decreases clockwise
S: if priority decreases counterclockwise
Cahn-Ingold-Prelog rules
- 18 of 21 amino acids are chiral…
- glycine is achiral…
- all are S configuration except for Sec and Cys are going to be R.
- side chains of isoleucine and threonine are chiral
Why are selenocystine and cystine in the R configuration?
There is a change in priority, the sulfur/selenium atom gains priority over the nitrogen
Condensation rxn to form amide/peptide bond occurs where
the ribosome
protein primary (1 ) structure
means the amino acid sequence
N to C convention
When we name amino acids we start at N terminus and go to C terminus… this is because its how theyre synthesized in ribosome
if EGAK is the amino acid sequence, is it the same as KAGE?
KAGE is a structural isomer of EGAK
enantiomer
pair of molecules that are mirror images of each other
diastereomer
Same molecular formula, non-superimposible, non-mirror images. (reversed stereochemistry in at least one)
