The amino acids introduction to basic chemistry

1. Amino Acids

2. Lesson Learning
Outcomes
Upon completion of this
lecture, students should be
able to:
• Understand the structures
and properties of amino
acids
• Know the groups of amino
acid

3. What are amino
acids?
• Amino acids are molecules
that when combined form
proteins.
• Amino acids contain a central
tetrahedral carbon
atom (α- carbon) , amine
group, carboxyl group, R-side chain
• The R-side chain determines the different
amino acids.
• An object or a system is chiral if it is
distinguishable from its mirror image;
that is, it cannot be superposed onto it.

6. There are 20 common amino acids
Amino acids can join via peptide bonds
Several amino acids occur only rarely in proteins
Some amino acids are not found in proteins

8. 3D structure of amino acids
• Why is the 3D structure (stereochemistry) of
amino acids important?
– Amino acids appear in chiral (mirror image) except
for glycine where the R = Hydrogen
– Chirality of amino acids can only be seen in 3D
structure

9. The position of amino group on the left or
right side of the α-carbon determines the L or
D designation.
L-amino acids are found in proteins
D-amino acids are often found in bacterial
cell walls and in some antibiotics.

11. Amino Acids Can Join Via Peptide Bonds

12. 20 Common Amino Acids
• Non-polar amino acids
• Polar, uncharged
amino acids
• Acidic amino acids
• Basic amino acids

14. (a) nonpolar (hydrophobic)

15. (a) nonpolar (hydrophobic)

16. (a) nonpolar (hydrophobic)

17. (b) polar, neutral

18. (b) polar, neutral

19. c) acidic

20. (d) basic

21. Several Amino Acids Occur Rarely in
Proteins
• Hydroxylysine, hydroxyproline - collagen
• Carboxyglutamate - blood-clotting proteins
• Pyroglutamate – in bacteriorhodopsin
• Phosphorylated amino acids – a signaling device

22. • Carboxyl group (-vely charged)
and amino group (+vely charged)
of the general structure – charged
at neutral pH
• Amino acids without charged
groups on their side chains exist in
a neutral solution- zwitterion
• Neutral amino acids do not exist
in the form of NH2-CHR-COOH.
Amino acids can act as
both acid and bases

24. Spectroscopic Properties
All amino acids absorb
infrared wavelengths
Only Phe, Tyr, and Trp
absorb UV.
Absorbance at 280 nm
is a good diagnostic
device for amino acids.
NMR (Nuclear
Magnetic Resonance)
spectra are characteristic
of each residue in a
protein.

25. Separation of Amino Acids
• Mikhail Tswett, a
separated colorful
Russian
plant
botanist, first
pigments by
‘chromatography’
• Many chromatographic methods exist for
separation of amino acid mixtures
–Ion exchange chromatography
–High-performance liquid chromatography

26. Chromatographic fractionation of a synthetic
mixture of amino acids on ion exchange
columns