Lipids Flashcards
Name 4 functions of lipids
Stored form of energy Structural element of membranes Enzyme co factors Hormones Vitamins A, D, E, K Signalling molecules
What are TAGs?
Triacylglycerols
Esters of FAs and glycerol
Give some properties of TAGs
Uncharged
Water insoluble
Fuel and insulation
Main dietary lipid
Describe Beta - oxidation
3 stages
Activation - fatty acid activated to form fatty acyl CoA in cytoplasm
Transport by Carnitine Shuttle - fatty acyl CoA is transported from cytoplasm to mitochondria by losing its CoA and binding to a carnitine shuttle (CAT-1)
Degradation - dehydrogenation Hydration Dehydrogenation Thiolysis
What is the main site of the digestion of lipids?
Small intestine.
What are the worst fatty acids?
Trans fatty acids - made from the hydrogenation of vegetable oils e.g margarine. Man made.
What are bile salts?
Act as biological detergents to form emulsions and mixed micelles. Aids digestion of lipids. Derived from cholesterol.
What are TAGs digested into?
Digested by pancreatic lipase in small intestine to form monoacylglycerol + 2 fatty acids.
What are cholesterol esters digested to?
Cholesterol and free fatty acid.
What are phospholipids digested to?
Lysophospholipid and fatty acid.
What happens to the digested lipids?
Form mixed micelles with bile salts. Mixed micelles approach brush border membranes of enterocytes and release lipid products which enter cells by diffusion.
Short and medium chain FA do not require micelles for absorption.
What is Steatorrhea?
Steatorrhea is excess fat in faeces. Stools float due to excess lipid, have an oily appearance and are foul smelling.
What happens to the absorbed fatty acids?
Re-synthesised by packaging them up with apoB-48 ( a soluble protein into Chylomicrons for export. These chylomicrons are then released by exocytosis into lymph, then blood.
What is the function of lipoprotein lipase?
Hydrolyses TAGs in chylomicrons into FA and glycerol.
Primarily found in capillaries of skeletal muscle and adipose tissue.
What can free FA be used for after it has been reabsorbed?
Used as energy or resynthesised an stored as TAG.