Biology Reference
In-Depth Information
Amino acids
Hydrophobic amino acids
Hydrophilic amino acids
1. Neutral amino acids
1. Neutral amino acids
-Glycine
-Cysteine
-Proline
-Serine
-Alanine
-Threonine
-Leucine
2. Acidic amino acids
-Isoleucine
-Aspartate
-Valine
-Glutamate
2. Aromatic amino acids
3. Basic amino acids
-Tryptophan
-Arginine
-Phenylalanine
-Histidine
-Tyrosine
-Lysine
4. Amino acid amides
-Asparagine
-Glutamine
Figure 1.2 Classification of amino acids based on chemical nature.
serine, tyrosine, selenocysteine) and are therefore deemed nonessential.
Recently, some amino acids have been classified as conditionally essential
(arginine, proline, cysteine, glycine) as they can be synthesized from amino
acid precursors (
Reeds, 2000
)
. However, this depends on the availability of
the precursors, some of which are essential amino acids. Foods containing all
the essential amino acids in quantities adequate to meet growth and repair
are termed complete protein foods (
Jeor et al., 2001
) and are exclusively
of animal origin. For the maintenance of proper nitrogen balance, it is
important to consume adequate amounts of complete proteins, or in their
absence, consume combinations of incomplete proteins with complemen-
tary amino acid compositions (
Jeor et al., 2001
).
