Proteins are organic polymers made up of chains of amino acids and are crucial material in many biological functions (Reece and others 2011). There are twenty basic amino acids, eight of which are essential to the adult human diet and must be consumed rather than synthesized within the body. These essential amino acids are isoleucine, leucine, tryptophan, lysine, valine, phenylalanine, methionine and threonine, with an additional requirement for histidine in the diet of children (Potter and Hotchkiss 1995). From these nonessential amino acids can be synthesized, and all amino acids are used as monomers to build proteins that perform numerous important functions in the body (Reece and others 2011). Most amino acids exist as isomers and receive a designation based on whether or not they rotate a plane of polarized light to the right or to the left, known respectively as right-handed “D” or left-handed “L” isomers (Al-Holy and Rasco 2007). It should be noted that only L amino acids are used in protein synthesis (Weber and Miller 1981). The biological functions of proteins include increasing the speed of biochemical reactions in the form of enzymes, moving important substances where they are needed in the form of transport proteins, regulating the body in the form of hormones, allowing the body to move in the form of contractile proteins and providing support in the form of structural proteins (Reece and others 2011). Furthermore, proteins have a large amount of functionality in foods, including providing essential amino acids as well as energy, viscosity, texture, water-holding capacity, foaming and emulsifying properties, and allowing gel formation (Culbertson 2007). As mentioned above, essential amino acids provided by th...... middle of paper ...... p.Reece JB, Urry LA, Cain ML, Wasserman SA, Minorsky PV, Jackson RB. 2011. Campbell Biology. 9th ed. San Francisco: Cummings Pearson. 1263 p.Siegwein AM, Vodovotz Y, Fisher EL. 2011. Soy protein isolate concentration affects the texture, sensoriality and keeping properties of starch-based desserts. J Food Sci 76:E422-8.Sorgentini DA, Wagner JR, Anon MC. 1995. Effects of heat treatment of soy protein isolate on the characteristics and structure-function relationship of soluble and insoluble fractions. J Agric Food Chem 43:2471-9.Thompson LD, Dinh T. 2009. Food proteins: protein isolation and thermal stability. FDSC 4303/5303 Food Chemistry Laboratory Manual. Lubbock, Texas: Texas Tech University, Department of Animal and Food Sciences. Weber AL, Miller SL. 1981. Reasons for the presence of the twenty protein-encoded amino acids. J Molecular evolution 17:273-84.