Page 4 - Lesson Notes - Biomolecules 1

The amino group accepts a proton whereas, the carboxyl group donates a proton.
So, an amino acid can act as both acid and base. Hence, it is amphoteric in nature.
The R group in these proteinaceous amino acids could be a hydrogen (glycine), a
methyl group (alanine), hydroxyl methyl (serine), etc.

The chemical and physical properties of amino acids are essentially due to the
amino, carboxyl and functional groups present.
Based on the number of amino and carboxyl group present, amino acids are
categorised into following types
i. Acidic Amino Acids
These contain one amino group and two carboxyl group per molecule, e.g., glutamic
acid and aspartic acid.
ii. Basic Amino Acids
These contain two amino groups and one carboxyl group per molecule, e.g., Arginine,
lysine and histidine.
iii. Neutral Amino Acids
These contain one amino group and one carboxyl group per molecule, e.g.,
Methionine, isoleucine, serine, threonine, cysteine, glycine, alanine, valine, leucine,
aspargine, glutamine and proline.