Glutamine
In human blood, glutamine is the most abundant free amino acid.
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 However, the idea that plant-based foods must be combined to provide humans all of the essential amino acids is outdated.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.