Glutamine
Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases, and glutamine must be obtained from the diet. It is encoded by the codons CAA and CAG.
Essential amino acid
Although plants tend to have less protein per weight than animal sources such as eggs or milk, they are nevertheless "complete" in that, as a whole, they contain all of the amino acids essential in human nutrition. The same is true for algae and marine phytoplankton. Eating various plant foods over an extended period of time can provide a protein of higher biological value. Certain native combinations of foods, such as corn and beans, soybeans and rice, or red beans and rice, contain the essential amino acids necessary for humans in adequate amounts. However, the idea that plant-based foods must be combined to provide humans all of the essential amino acids is outdated. The official position of the Academy of Nutrition and Dietetics is that protein from a variety of plant foods eaten during the course of a day supplies enough of all essential amino acids when caloric requirements are met.