Alanine and glutamine crystals. Polarized light micrograph of crystals of the amino acids beta-alanine and l-glutamine. Alanine is a non-essential amino acid (one that can be synthesized by the body). It plays an important role in the production of urea, the principal form in which mammals excrete nitrogenous compounds from the body. Glutamine is also a non-essential amino acid. It is used in protein synthesis and to support the production of the antioxidant glutathione. Immune system weaknesses and nerve problems can occur during times of high demand for glutamine. Magnification: x25 when printed at 10 centimetres wide.