This presentation the chemical structure of natural amino acids. It also classifies amino acids according to several criteria e.g., structure (aliphatic, aromatic, and heterocyclic amino acids), reaction (Neutral, acidic and basic amino acids), polarity (polar and nonpolar amino acids), and metabolic fate ( glucogenic, ketogenic and glucoketogenic amino acids)

1. Amino acids
•Physiological importance
•Classification
•Properties

13. Net charge of amino acids at neutral pH:
At physiologic pH, all amino acids have a
negatively charged group (–COO-) and a
positively charged group (–NH3
+), both
attached to the α-carbon. [Note:
Glutamate, aspartate, histidine, arginine,
and lysine have additional potentially
charged groups in their side chains.]
Substances, such as amino acids, that can
act either as an acid or a base are defined
as amphoteric, and are referred to as
ampholytes (amphoteric electrolytes).
They function as physiological buffers.
Note: pI of histidine is very close to 7.4

17. V. Chapter Summary
•
Each amino acid has an α-carboxyl group and
a primary α-amino group (except for proline,
which has a secondary amino group). At
physiologic pH, the α-carboxyl group is
dissociated, forming the negatively charged
carboxylate ion (–COO-), and the α-amino
group is protonated (–NH3
+). Each amino acid
also contains one of twenty distinctive side
chains attached to the α-carbon atom. The
chemical nature of this side chain determines
the function of an amino acid in a protein, and