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18 terms

Digestion and Transport of Dietary Lipids

Lecture 49
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cholesterol
has 27 carbons, 1 hydroxy group, it is a flat molecule that is very hydrophobic and converts to bile acids
bile acids
2 additional hydroxy groups and a COOH group added to the cholesterol, hydrophilic on one side and hydrophobic on the other (amphipathic) and is kinked
NPC1L1
dietary cholesterol is absorbed into enterocytes by diffusion and by this, a cholesterol transporter
ABCA1
cholesterol effluxes out of enterocytes via this transporter
ABCG5/ABCG8
plant sterols are excreted via these transporters - deficiency causes sitosterolemia
triglycerides
the major fat in the human diet consisting of three fatty acids esterified to a glycerol backbone - produced in the SER of intestinal epithelial cells
2-monoacylglycerol
the main route for degradation of triglycerides involves hydrolysis to fatty acids and this
bile salts
derived from cholesterol - emulsifies fats in the small intestine - synthesized in the liver, stored in the gallbladder and secreted into the intestinal lumen - act as detergents, binding to the globules of fat
cholecystokinin
secreted by the intestine, signals the gallbladder to contract and release bile acids, and the pancreas to release digestive enzymes
bile acids
activate pancreatic lipases
colipases
increase lipase activity to digest triglycerides to monoacylglycerol and free fatty acids
cholesterol esterases
hydrolyze cholesterol esters to free cholesterol and fatty acids
micelles
bile acids emulsify fatty acids and monoacylglycerol to form ____ - must reach 5-15 mM CMC to form
chylomicrons
contain 85% TG, Apo B-48, cholesterol esters, phospholipids, and fat-soluble vitamins - assembled in both ER and golgi complex and secreted into lymph
ApoB48
synthesized in the rough ER
nascent CMs
secreted into the lymphatic system and enter the blood through the thoracic duct - receive ApoCII and ApoE from HDL to form mature CM
ApoE
recognized by membrane receptors, LDL receptor-related proteins
ApoCII
activates LPL located on the surface of the capillary endothelial cells in muscle and adipocytes, and digest TG to release free FAs from CM and VLDL