BIOL 1840U Lecture Notes - Ileum, Endoplasmic Reticulum, Chylomicron
Document Summary
Physical event to generate small fat droplets: lipolysis by pancreatic enzymes. Lingual lipase: cleaves short tgs, only important in infants. Pancreatic lipase: cleaves 1 and 3 position of tg, active at fat-water interface, large reserve and colipase protect lipase against bile acid inactivation. Phospholipase a2: cleaves 2 position of phospholipid. Non-specific esterases: e. g. cholesterol esterase: solubilization by bile salts. Bile salts form mixed micelles with ffa"s and 2-mg"s: diffusion to the mucosa. Increased concentration of solubilized fa drives flux to mucosal cell. Some fatty material does not require hydrolysis but only micellar solubilization. Small fa do not require solubilization; they diffuse directly to mucosa. Tgs are completely hydrolyzed prior to uptake. Fa uptake in proximal small intestine, but bile salts absorbed in ileum. Mechanism of uptake into cells is unclear, but does not require energy: transport to the endoplasmic reticulum. Z protein may be involved in fa binding and transport to er: resynthesis of triglycerides.
