1. Amino Acids Amine group -NH2 Carboxylic group -COOH
Functional group
There are many different aminoacids, but those where –NH2 and –COOH are
attached to the Ca atom (a aminoacid) are of special interest in biology.

2. Amino Acids Ca 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 N C
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.
Functional group

3. The 20 amino acids Thr (T) Phe (F) Val (V) Ala (A) His (H) Arg (R)
Ser (S)
Leu (L)
Cys (C)
Met (M)
Asp (D)
Lys (K)
Asn (N)
Ile (I)
Trp (W)
Gln (Q)
Glu (E)
Tyr (Y)
Pro (P)
Gly (G)

4. Summary – protein II

5. Basic amino acids
Arg (R)
Can be protonated H+
Lys (K)
His (H)

6. Acidic amino acids
-C-OH O
-C-O- O
+ H+
Asp (D)
Glu (E)

7. 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)

8. Aromatic amino acids Aromatic amino acids all have
a flat planar group as part of
the sidechain.
Which of these are:
Hydrophobic?
Polar?
Charged?
Phe (F)
His (H)
Tyr (Y)
Trp (W)

9. Special amino acids Why are they special? Cys-Cys Sidechain connected
Pro (P)
Gly (G)
Cys-Cys
Sidechain connected
to backbone
Has two identical
Atoms connected to
Ca – therefore not
Chiral Ca