Amino acids are small organic molecules that play several significant roles in living organisms.: They are the principal building blocks of proteins. They serve as precursors for many biologically active molecules, such as neurotransmitters, local mediators , energy-related metabolites the oxygen-binding molecule ‘heme‘, and DNA bases called purines. They serve as an energy source during prolonged fasting, diabetes, and when the diet is rich in proteins. Some amino acids act as regulators of gene expression and cellular signaling. This affect multiple physiological processes that are related to growth, maintenance, reproduction and immunity.

1. Amino Acids
By Prof. Liwayway Memije-Cruz

2. General Structure of
Amino Acid

3. What are Amino Acids?
Amino acids are small organic molecules that play several important
roles in living organisms:
 principal building blocks of proteins
 serve as precursors for many biologically active molecules, such as
neurotransmitters (e.g. dopamine, serotonin, GABA, epinephrine),
local mediators (e.g. the allergy mediator histamine), energy-related
metabolites (e.g. creatine, citrulline, carnitine), the oxygen-binding
molecule ‘heme‘, and DNA bases called purines.
 serve as an energy source during prolonged fasting, diabetes, and
when the diet is rich in proteins.
 some act as regulators of gene expression and cellular signaling. This
affect multiple physiological processes that are related to growth,
maintenance, reproduction and immunity.

4. Physio and chemical properties of amino
acids
1. Solubility: Most of the amino acids are usually soluble in water, and
insoluble in organic solvents.
2. Melting Point: Amino acids generally melt at higher temperature of ten
above 2000C.
3. Taste: Amino acids may be sweet (Gly, Ala & Val), tasteless (Leu) or
Bitter (Arg & Ile).
4. Optical Properties: All amino acids possess optical isomers due to the
presence of asymmetric α-carbon atoms.
5. Zwitter ion and Isoelectric point: The name zwitter is derived from the
German word which means “hybrid”. Zwitter ion (or) dipolar ion is a
hybrid molecule containing positive & negatively ionic groups. Basically
the proton shifts from carboxyl group to amino group of the self molecule
at normal pH cellular levels.
6. Titration Curve of Glycine: Glycine is optically inactive, simplest
amino acid because which have no asymmetric carbon atom. Acid-Base
titration involves the gradual addition (or) removal of protons. It has
three different stages when the Glycine undergoes acid-base titration.

5. The 20 naturally-occurring amino acids can
be clustered according to their physical-
chemical properties

6. The 20 types of amino acids

7. Nonpolar aliphatic R groups

8. Polar uncharged R groups

9. Aromatic R groups

10. Positively charged R groups

11. Negatively charged R groups

12. Amino Acids Groups
• It is customary to group the 20 natural amino acids found
in proteins into 4 types, according to the polarity of their
side chains.
• Amino acids that have polar side chains are hydrophilic:
they tend to appear on the surface of water-soluble
proteins where they can interact favorably with the
surrounding water.
• Amino acids that have nonpolar side chains are
hydrophobic: they tend to be buried inside proteins, where
they are away from water and can interact favorably with
each other.

13. Nonpolar Amino Acids

14. Polar-uncharged amino
acids

15. Polar charged amino acids

16. Aromatic amino acids

17. 20 Kinds of Amino Acids that
Support the Body

18. Amino Acids Food Sources

19. Protein and Amino Acids
 Proteins are essential for energy and growth. They are the building
blocks of life and are in every cell of the human body. Protein
foods are broken down into amino acids during digestion and are
intricate in growth and tissue repair. Amino acids are therefore the
link between the proteins we eat and assimilation for our body
tissue. While adequate amounts of protein and amino acids aid
healing after bariatric surgery, a lack of adequate amino acids may
make it impossible for vitamins and minerals to perform their
specific duties.
 Protein and amino acids are important for survival and recovery.
They preserve active tissue mass and maintain other functions, as
well. Studies are being conducted to assess protein status and
outcomes of protein nutritional support for recovery and
preservation of muscle mass among critically ill patients.
Identifying a target for provision of protein to patients will help
recognize the role of protein in nutrition support, particularly for
obese patients.

21. References:
• https://amit1b.wordpress.com/the-molecules-of-
life/about/amino-acids/
• https://www.biochemden.com/physio-chemical-
properties-of-amino-acids/
• http://www.mybariatriclife.org/protein-and-amino-acids-
after-bariatric-surgery/#prettyPhoto