Proteins not only catalyze all (or most) of the reactions in living cells, they control virtually all cellular process.

Proteins are about 50% of the dry weight of most cells, and are the most structurally complex macromolecules known.
A protein forms via the condensation of amino acids to form a chain of amino acid "residues" linked by peptide bonds. Proteins are polymers of about 20 amino acids.

Polymers are any kind of large molecules made of repeating identical or similar subunits called monomers. The starch and cellulose are polymers of glucose, which in that case, is the monomer.
(the monomer).

In chemistry, an amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids built from a central alpha carbon bonded to an amino group, (-NH2), a carboxyl group (-COOH), a a hycrogen (H) and side chains (R-group) of increasing complexity.

that are relevant to the make-up of mammalian proteins

phenylalanine, an essential amino acid, is a derivative of alanine with a phenyl substituent on the b carbon.

Related to other organic groups containing rings of carbon atoms, this Aromatic amino acid has a side chain derived from a benzene ring by removal of one hydrogen atom. Tending to be buried in regions where water is excluded, this Non Polar amino acid is not water soluble, and is a very hydrophobic. Used by the brain as a natural precursor to the manufacture of norepinephrine and other neurotransmitters, it enhances learning, alertness and memory. Also used in the treatment of depression, and the 'D' form Phenylalanine acts as a pain killer. Nutritional conflicts may occur unless kept in balance with other amino acids through dietary intake.

All peptides and polypeptides are polymers of alpha-amino acids. There are 20 α-amino acids that are relevant to the make-up of mammalian proteins.

Table at indstate.edu
Amino Acids and Proteins at U. Cincinnati
The Chemistry of Amino Acids at U. Arizona
amino acids at Colorado State
Tutorial on peptide and protein structure