Lipids Flashcards
What do lipids exist as in adipose tissue?
lipid droplets
What do lipids exist as in blood?
lipoproteins
What is the structure of fatty acids?
Hydrophobic hydrocarbon ‘tail’ and hydrophilic terminal carboxyl group
What is the name of the lipid class that gives rise to blood group antigens?
glycolipids (consitituent of membranes)
What makes a fatty acid unsaturated?
has one or more double bonds that kink the hydrocarbon chain, liquid
What are examples of essential fatty acids?
linoleic and alpha linolenic acid
What are good fatty acids?
high in polyunsaturated fatty acids
What are bad fatty acids?
high in saturated fatty acids
What are really bad fats?
trans fatty acids resulting from hydrogenation of vegetable oils
What is linoleic acid a substrate for?
prostaglandins and arachidonic acid which is a precursor of eicosanoids (signalling molecule)
What is linolenic acid a substrate for?
omega 3 fatty acids
What do omega 3 fatty acids do?
lower plasma cholesterol preventing atherosclerosis and lowers TAG preventing obesity
What are triacylglycerols?
esters of fatty acids and glycerol which are uncharged and water insoluble therefore form droplets
What do TAGs do?
dietary fuel and insulation
What are phospholipids composed of?
2 fatty acids and glycerol and a phosphate group
What does ‘amphipathic’ mean?
Has both hydrophilic and hydrophobic parts
What is the main dietary lipid?
TAG
Where is the main site of lipid digestion?
small intestine
What enzymes digest lipids?
lipases
What is lipid digestion promoted by?
emulsiification by bile salts and peristalsis
What do bile salts do?
act as biological detergents to form emulsions and mixed micelles
are derivatives of cholesterol
saves lipids coalescing in an aqueous environment
How do we digest TAG?
degraded in small intestine by pancreatic lipase to monoacylglycerol and 2 fatty acids as is too big to be taken up by mucosal cells in intestinal villi
What are cholesterol esters digested to?
cholesterol and free fatty acid
What are phospholipids hydrolysed to?
FA and lysophospholipid
How are digested lipids absorbed?
products form mixed micelles with bile salts
mixed micelles approach brush border membranes of enterocytes and release lipid products which enter cells by diffusion
What FAs don’t need micelles for absorption?
short and medium chain FAs
What is steatorrhea?
excess fat in faeces due to lipid malabsorption
What patients are prone to developing steatorrhea?
cystic fibrosis affected patients
What are 2 possibilities of the utilisation of dietary lipids after fatty acids are absorbed?
intestinal cells resynthesises TAG, phospholipid, cholesterol ester for export
or are packaged into chylomicrons to make them soluble and released into lymph by exocytosis and then into blood
What does lipoprotein lipase do?
hydrolyses TAG in chylomicrons to FA and glycerol
Where is lipoprotein lipase mainly found?
in capillaries of skeletal muscle and adipose tissue
Where do chylomicron remnants go?
liver
What is glycerol in the liver used to do?
produce glycerol-3-phosphate which can be used in glycolysis and gluconeogenesis
How are FAs released from stored TAG in tissues?
Hormone sensitive lipase (HSL)
What is HSL activated by?
phosphorylation in response to epinephrine
How are free FAs transported in the blood?
lipoproteins
in complex with serum albumin
What do chylomicrons carry and from where to where?
TAG
intestine to tissues
VLDL carry and to where?
TAG
liver to tissue
LDL
cholesterol
to tissues
HDL
cholesterol
tissue to liver for elimination
