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:
“To have that sense of one’s intrinsic worth which constitutes self-respect is potentially to have everything: the ability to discriminate, to love and to remain indifferent. To lack it is to be locked within oneself, paradoxically incapable of either love or indifference.”
—Joan Didion (b. 1934)
“In his very rejection of art Walt Whitman is an artist. He tried to produce a certain effect by certain means and he succeeded.... He stands apart, and the chief value of his work is in its prophecy, not in its performance. He has begun a prelude to larger themes. He is the herald to a new era. As a man he is the precursor of a fresh type. He is a factor in the heroic and spiritual evolution of the human being. If Poetry has passed him by, Philosophy will take note of him.”
—Oscar Wilde (1854–1900)