Amino Acids Flashcards
Non polar AA
Glycine (neither) Alanine Proline Valine Leucine Isoleucine Methionine
Polar
Serine Threonine Cystine Asparagine Glutamine
Aromatic
Phenylalanine
Tyrosine
Tryptophan
Positively charged
Lysine
Arginine
Histadine
Negatively charged
Aspartate
Glutamate
Non standard AA
4-hydroxyproline
5-hydroxylysine
Both found in collagen
What is a zwitterion
Very rare for aa to form non ionic so AA exist as a zwitterton meaning they can act as a base (amine group at high ph) or an acid (carboxyl group at low ph)
Three stage titration curves
4 charge states
Positive Negative
Lysine Aspartate
Arginine Glutamate
Histadine
Asparagine Glutamine Phenylalanine Tyrosine Tryptophan Lysine Arginine Aspartate Glutamate
Asparagine N Glutamine Q Phenylalanine F Tyrosine Y Tryptophan W Lysine K Arginine R Aspartate D Glutamate E
Summary of peptide bond formation
Carboxyl group becomes a ketone
Amine becomes amuse
No longer ionisable
Condensation reaction
Histidine charge state
Therefore positively charged AA
+2
+1
0
-1
So PI between top two pKa’s
Glutamate
Aspartate charge states
+1
0
-1
-2
So Pi between bottom two PKA’s
Non ionising r group = glycine
What are charge states
-1
0
+1
PI = average of two
Order of basidity
Lysine, arginine and histidine
Histadine then lysine lastly arginine because it has gunidine which is VERY basic
