Briefly discuss the absorption process and sites of biotin, folate. cobalamin, and ascorbic acid
In essence, human beings cannot synthesize biotin, and therefore the vitamin is required in water soluble form to perform the normal cellular function. The absorption process of biotin takes place in the small and large intestines (Said, 2011). The process involves the Na+ carrier that transports the vitamin in human beings. The sodium-dependent transports, also written as hSMVT is expressed in the apical membrane of the enterocytes.
Folates exist as polyglutamate in the diet, which enables them to be converted to mono glutamates through an enzymatic process. The absorption process of the vitamin takes place in the intestines with the help of a carrier, which is known as enzyme folypoly-y-glutamate carboxypeptidase (Said, 2011). The large intestines also play a critical role in the absorption of folate, which intakes the bacterial-provided vitamin that exists as folate mono glutamate.
Fundamentally, Cobalamin is ingested in the diet in its protein-bound form. The proteins undergo the proteolytic cleavage process in the duodenum or the stomach. In this site, the protein carrier, which is known as the R-binder that facilitates the absorption process (Busti, 2015). In the pancreases also secretes protease that degrades the R-binders in the cobalamin. From this point, the vitamin proceeds to the small intestines for absorption and later utilized in the body.
The absorption of ascorbic acid in humans takes place in the gastrointestinal tract. Ascorbic acid is first oxidized to form a dehydroascorbic acid that can move across the cell membranes (Said, 2011). Important to note, the transportation process depends on the differences in tissue specificity, kinetics, energy dependence, and Na+. The dehydroascorbic acid is further reduced intracellularly through both chemical and enzymatic mechanisms to form ascorbate.
References
Busti, A. (2015). The mechanisms of absorption of Vitamins B12 (Cobalamin) in the GI tract. EBM Consultant. Retrieved from http://www.ebmconsult.com/articles/vitamin-b12-absorption-mechanism-intestine-intrinsic-factor.
Said, H. M. (2011). Intestinal absorption of water-soluble vitamins in health and disease. Biochemical Journal, 437(3), 357-372.
