Amino acids are the building block of proteins. Here we discuss about 20 standard amino acids.

1. Ayesha Nawaz (2018-2314)
Presented to:
Ma'am Ayesha
B.S.Ed.(Hons)
Punjab University Lahore

2. STANDARD AMINO ACIDS:
• More than 300 naturally occurring amino acids
are known, but only 20 amino acids take part in
making all types of proteins.
• These 20 amino acids are called primary,
standard or normal amino acids.
• Each amino acid have one or more genetic codon
which are present within the molecules of
specific messenger RNA which themselves
produced under direction of genes occurring in
DNA molecules.

3. A list of standard amino acids with structural
formulae are given below:
• Simplest amino acids and only amino acids which
has no asymmetric carbon atom. Glycine(Gly) and
alanine(Ala) are sweetest in taste.

4. SERINE:(Ser)
Its OH group can
participate in hydrogen bonding or
in binding with phosphate or
carbohydrate.
THREONINE:(Thr)
Like serine it also has a
OH group.

5. Valine (val) Leucine (Leu) and Isoleucine (Ile)
have branched chain. Valine and isoleucine are 5
carbon compound and leucine is 6 carbon
compound.

6. CYSTEINE:(Cys)
Its sulfhydral group
is an important component of the
active site of many enzymes.
Two molecules of cysteine on
being oxidized can combine with
each other through covalent –S-
S- linkage forming the dimer
compound cysteine .
METHIONINE : (Met)
Cysteine and
methionine are sulphur
containing amino acids.

7. Cysteine formation takes place in structure of proteins after
the latter have been synthesized; this is called post
translational modification.

8. Phenylalanine(Phe), Tyrosine(Tyr) and
Tryptophan (Trp) contain aromatic rings in their
molecules. And tyrosine was named so because it
was first isolated from cheese which in Greek is
tyros.

9. ASPARTIC ACID: (Asp)
At pH 7 it has one
net negative charge .
ASPARAGINE: (Asn)
It is the amide of
aspartic acid. It was the first
amino acid to be discovered in
1806 and it was named so
because it was isolated from
asparagus.

10. GLUTAMIC ACID:(Glu)
It was first found to
occur in wheat protein
namely gluten. At pH 7 it
has one net negative
charge.
GLUTAMINE:( Gln)
It is the amide of
glutamic acid.