Download Aminoacids_followup

Amino Acids
Amine group
-NH2
Carboxylic group
-COOH
There are many different aminoacids, but those where –NH2 and –COOH are
attached to the Ca atom (a aminoacids) are of special interest in biology.
Amino Acids
Ca
N
C
In a protein there are some atoms that
all aminoacids have in common i.e. the
4 backbone atom: N, Ca, C and O
O
Sidechain attached here at Ca
Indicated with R
An amino acids with 4 different atoms attached to the Ca atom is chiral.
One aminoacid Gly has a sidechain which is a hydrogen ’H’ – therefore this
amonoacid has 2 identical groups/atoms attached to the Ca atom and it is
therefore not chiral.
The 20 amino acids
Thr (T)
Phe (F)
Val (V)
Ala (A)
His (H)
Arg (R)
Ser (S)
Leu (L)
Cys (C)
Asp (D)
Met (M)
Lys (K)
Asn
(N)
Ile (I)
Trp (W)
Glu (E)
Gln
(Q)
Tyr (Y)
Pro (P)
Gly (G)
Summary – protein II
Basic amino acids
Arg (R)
His (H)
Can be protonated
H+
Lys (K)
Acidic amino acids
O
-C-OH
Asp (D)
Glu (E)
O
-C-O-
+ H+
Amino acids with hydroxyl group
In biology hydroxyl groups –OH are important as they can be modified
by different molecules as phosphate (-PO4) or a long range of
sugar (carbohydrate) molecules
Ser (S)
Thr (T)
Tyr (Y)
Aromatic amino acids
Phe (F)
His (H)
Aromatic amino acids all have
a flat planar group as part of
the sidechain.
Which of these are:
Hydrophobic?
Polar?
Charged?
Tyr (Y)
Trp (W)
Special amino acids
Why are they special?
Cys (C)
Pro (P)
Sidechain connected
to backbone
Cys-Cys
Gly (G)
Has two identical
Atoms connected to
Ca – therefore not
Chiral Ca