Basic structure: C a , amino group, carboxyl group, and R-group.

C a is the chiral center: D- and L-amino acid (enantiomer).

Proteins are made almost exclusively of L-amino acids.

The property of the amino acid is largely defined by the R-goup.

Amino acid is a zwitterion , it can act as an acid or a base.

The titration curve of an amino acid with non-ionizing R-group is simple, with two buffering zone.

The titration curve can be complicated with an ionizing R-group.

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