Overview Vitamin B12 (Cobalamin) absorption occurs in terminal ileum requires intrinsic factor (IF) gastrectomy IF deficiency as a consequence of loss of parietal cells IF deficiency → vitamin B12 deficiency may cause pernicious anemia treatment is vitamin B12 administered by injection Iron (Fe) absorption occurs in duodenum absorption across apical membrane of intestinal epithelial cells occurs as free iron (Fe2+) in intestinal epithelial cells, free iron (Fe2+) binds apoferritin iron-ferritin complex is transported across basolateral membrane into bloodstream in bloodstream, iron binds transferrin and is transported from intestine to storage sites in liver absorption across apical membrane of intestinal epithelial cells may also occur as heme iron in intestinal epithelial cells, heme iron (iron bound to hemoglobin) is digested by lysosomal enzymes releases free iron (Fe2+), which binds apoferritin Folic acid (folate) absorption occurs in the jejunum small reserve pool stored in the liver