AMINO ACID CHEMISTRY Flashcards
Show the general structure of an amino acid and label the asymmetric carbon atom (LO)
draw 20 amino acid (esp GLY,GLU,HIS)
Show the difference between D and L amino acids (LO)
L- Nh2 on the left ( found in nature)
D -NH2 on the right
Define standard and non-standard amino acid with exp(LO)
Standard- AA for which at least one codon exists in the genetic code
Non-standard- consist of AA residues that have been chemically modified aft incorporation into polypeptide
List few exp of amino acid modified post-translationally(SLS). (LO)
4-hydroxyproline- hydroxylation of proline residues aft incorporation into polypeptide chains. in collagen
5-hydroxylysine- hydroxylation of lysine residues aft incorporation into polypeptide chains. in collagen
gamma- carboxyglutamate- carboxylation of conversion of glutamate.in prothrombin
methyl lysine- methlyation of lysin. in histone proteins
Diphthamide- methylation of histine. in elongation factor 2( involved in DNA regulation)
Amino acids are ampholytes
they contain both basic(amino) and acidic(carboxyl) grps.
define alpha carbon
carbon that is linked to the carboxylate, amino and R groups
Which amino acid does not have a primary amino grp?
Proline (secondary amino grp)
pH 7.4
coo-,NH3+ formed ( Zwitter ion)
what is asymmetric carbon atom/ chiral carbon?
A carbon atom attached to 4 dif types of atoms/ grp of atom
Which standard AA is symmetric?
Glycine because its R grp is H atom.no chiral carbon. no optical rotation
describe stereoisomers
- not superimposable
- mirror images called enantiomers
- D and L enantiomers have dif optical rotation
state 5 common D amino acids
D-serine
D- aspartate
D- phenylalanine
D-alanine and D glutamate
D-serine
- in mammal brains
- co- agonist of NMDA type glutamate receptors responsible for learning,memory and behaviour
- Alzheimers
D- aspartate
-regulator in adult neurogenesis
- Alzheimers
- development of endocrine function ( mainly in pituitary gland and testes), regulation of the release and synthesis of LH
D- phenylalanine
in cyclic peptide antibiotics tyrocidin and gramicidin S
-decrease pain
D-alanine and D glutamate
in cell walls of gram positive bacteria
-involved in peptidoglycan biosynthesis
dextrorotary behavior
+ form with clockwise rotation (rotate the plane of plane-polarized light.
levorotary behavior
- form with anticlockwise rotation
L enantiomer that is dextrorotary.
L (+) alanine
which AA does not have D and L forms.
Glycine has H atom as a side chain
- does not have chiral C
-does not form stereoisomers
- no D or L configurations
- no chiral C, does not rotate the plane of plane-polarized light.
Name AA with 2 assymetric C atoms. and num of their stereoisomers
Isoleucine and threonine
2 power of n= 4 stereoisomers possible
which AA can be involved in buffering
GLU AND HIS
Which amino acid is an imino acid
Proline
standard amino acids
all 20
non-standard AA
AKA Non-protein AA
post translationally modifies amino acids: hydroxyproline
derived alpha AA- Ornithine,Citrulline,Homocystein( high mean high cardio disease risk)
non-derived alpha AA- beta-alanine,GABA(gamma amino butyric acid)
define post-translational modification of an AA
AA in protein from chemical modification of standard amino acids
