Chapter16Fall2005 - Chapter 16 - Lipid Metabolism Fatty...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 16 - Lipid Metabolism Fatty acids have four major physiologic roles in the cell: Building blocks of phospholipids and glycolipids Added onto proteins to create lipoproteins, which targets them to membrane locations Fuel molecules - source of ATP Fatty acid derivatives serve as hormones and intracellular messengers Absorption and Mobilization of Fatty Acids Most lipids are triacylglycerols, some are phospholipids and cholesterol. Digestion occurs primarily in the small intestine. Fat particles are coated with bile salts (amphipathic) from gall bladder. Degraded by pancreatic lipase (hydrolyzes C-1 and C-3 ---> 2 fatty acids and 2- monoacylglycerol). Can then be absorbed by intestinal epithelial cells; bile salts are recirculated after being absorbed by the intestinal epithelial cells. In the cells, fatty acids are converted by fatty acyl CoA molecules. Phospholipids are hydrolyzed by pancreatic phospholipases, primarily phospholipase A 2 . Cholesterol esters are hydrolyzed by esterases to form free cholesterol, which is solubilized by bile salts and absorbed by the cells. Lipids are transported throughout the body as lipoproteins . Lipoproteins consist of a lipid (tryacylglycerol, cholesterol, cholesterol ester) core with amphipathic molecules forming layer on outside. Lipoproteins Both transported in form of lipoprotein particles, which solubilize hydrophobic lipids and contain cell-targeting signals. Lipoproteins classified according to their densities: o chylomicrons - contain dietary triacylglycerols o chylomicron remnants - contain dietary cholesterol esters o very low density lipoproteins (VLDLs) - transport endogenous triacylglycerols, which are hydrolyzed by lipoprotein lipase at capillary surface o intermediate-density lipoproteins (IDL) - contain endogenous cholesterol esters, which are taken up by liver cells via receptor-mediated endocytosis and converted to LDLs o low-density lipoproteins (LDL) - contain endogenous cholesterol esters, which are taken up by liver cells via receptor-mediated endocytosis; major 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
carrier of cholesterol in blood; regulates de novo cholesterol synthesis at level of target cell o high-density lipoproteins - contain endogenous cholesterol esters released from dying cells and membranes undergoing turnover Storage of Fatty Acids Triacylglycerols are transported as chylomicrons and VLDLs to adipose tissue; there, they are hydrolyzed to fatty acids, which enter adipocytes and are esterified for storage. Mobilization is controlled by hormones, particularly epinephrine, which binds to β - adrenergic receptors on adipocyte membrane --> protein kinase A activated --> phosphorylates hormone-sensitive lipase --> converts triacylglycerols to free fatty acids and monoacylglycerols.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/02/2009 for the course BIOCHEMIST 100 taught by Professor Crew during the Spring '05 term at North Alabama.

Page1 / 8

Chapter16Fall2005 - Chapter 16 - Lipid Metabolism Fatty...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online