Intrinsic factor (IF) also known as gastric intrinsic factor (GIF) is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B12 later on in the small intestine. In humans, the gastric intrinsic factor protein is encoded by the GIF gene.
Upon entry into the stomach, vitamin B12 becomes bound to haptocorrin (R factor), a glycoprotein. The resulting complex enters the duodenum, where pancreatic enzymes digest haptocorrin. In the less acidic environment of the small intestine, B12 can then bind to intrinsic factor. This new complex travels to the ileum, where special epithelial cells endocytose them. Inside the cell, B12 dissociates once again and binds to another protein, transcobalamin II. The new complex can exit the epithelial cells to enter the liver.
Read more about Intrinsic Factor: Site of Secretion, Clinical Significance, Treatment, Model Organisms
Famous quotes containing the words intrinsic and/or factor:
“Wherever there are walls I shall inscribe this eternal accusation against Christianity upon them—I can write in letters which make even the blind see ... I call Christianity the one great curse, the one great intrinsic depravity, the one great instinct for revenge for which no expedient is sufficiently poisonous, secret, subterranean, petty—I call it the one immortal blemish of mankind....”
—Friedrich Nietzsche (1844–1900)
“Children of the middle years do not do their learning unaffected by attendant feelings of interest, boredom, success, failure, chagrin, joy, humiliation, pleasure, distress and delight. They are whole children responding in a total way, and what they feel is a constant factor that can be constructive or destructive in any learning situation.”
—Dorothy H. Cohen (20th century)