basic concepts of amino acids

1. Vaishnavi Tutorial
My Education :-
MSc. ( Microbiology )
With B.Ed.
Amino acids

2. Amino acid
 What are amino acids ?
 Structure of amino acids.
 Amino acids act as acids or base
 Optical properties of amino acids.
 Absolute configuration
 Standard and Non -standard amino acids.

3. What are amino acids
 Amino acids are compound containig carbon , oxygen, hydrogen
and nitrogen and serve as monomers of proteins.
 Amino acid are building block of proteins .
 Amino acid are a group of organic compound containing two
functional groups amino and carboxyl.
 Amino acids are forming part of coenzymes.
 Amino acids uses as precursors for the biosynthesis of molecules
such as heme

5. Structure of amino acids
 Amino acid term as alpha- amino acids.
 Alpha- amino acid in which amino and carboxylic group is
attached to the same carbon atom, which is called alpha-
carbon atom .
 The various alpha-amino acid differ with respect to the side
chain ( R-group) attached to their alpha-carbon.
 Different type of amino acids based on the chemical nature of
side chain (R-group)

6. Different type of amino acids based on the chemical nature of
side chain (R-group)

7. Amino acid act as acids or base
 When an amino acids is dissolved in water, it exist as dipolar ion
or zwitterions.
 Zwitterion act as either an acid (proton donor) or a base (proton
acceptor) Hence an amino acid is amphoteric in nature
 At high concentration of hydrogen ions ( low pH) , the carboxyl
group protonated and become uncharged whereas amino
group is protonated and become positively charge , thus overall
charge becomes positive.
 Similarly , at high pH the amino group deprotonated and
become uncharged whereas carboxylic group deprotonated and
become negative charge, thus the overall charge become
negative

9. Optical properties of amino acid
 All amino acid except glycine are optically active i.e. they rotate
the plane of polarized light.
 Optically active molecules contain chiral carbon. Chiral carbon
contains four different groups linked to it at a time.
 All amino acids except glycine are optically active.
 An optically active compound can rotate the plane of the
polarized light in two direction.
 Clockwise – to the right, dextrorotatory(+) (D)
 Counterclockwise – to the left (-) (L)
 Optical activity is measured by polarimeter. The quantitative
measure of the optical activity of a molecule is its optical
rotation

10. Optical properties of amino acids

11. Absolute configuration
 A chiral amino acid can exist in two configuration that are non-
superimposable mirror images of each other.
 This two configuration are called enantiomers.
 When the amino grp is on the left of the chiral carbon, the
configuration is L, when it is on the right, configuration is D.

12. • All amino acids except glycine exists as DL
system.
• All the amino acids ribosomically incorporated
into protiens exhibit L- configurtion, all are L-
alpha amino acids.
• D form of amino acids are not found in protiens,
but they do exist naturally and are present in
some peptide antibiotics and peptidoglycan cell
wall of bacteria.

13. Standard and Non- standard
 Amino acids participate in protein synthesis, which
are incorporated ribosomically into proteins such
amino acids are called standard amino acids.
 Amino acids that occur naturally in cell but are not
incorporated ribosomically into proteins are called
non-standard amino acids.
 Some nonstandard amino acids are constituents of
ribosomically synthesized protein but they are
generated by post-translation modification of standard
amino acids which are incorporated ribosomically into
proteins.

14. Standard amino acids
 300 different amino acids present in nature.
 Only 22 different amino acids are standard amino acids, i.e.
participate in protein synthesis.
This standard amino acid classified in three types.
Amino acids
with nonpolar
side chain
Amino acids with
uncharged polar
side chain
Amino acids with charged
polar side chain

15. Amino acids with nonpolar side chain
 Glycine , Alanine, Valine, Leucine, Isoleucine,
Proline, Methionine, Phenylalanine, Tryptophan.

16. Amino acids with uncharged polar
side chain