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18 Cards in this Set
- Front
- Back
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Fatty Acid Structure |
Carboxyl Group with Hydrocarbon Chain The degree of packing/aggregation depends on the degree of saturation Cis double bonds restrict rotation |
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Names and Numbers |
Lauric Acid= 12C Miristic Acid = 14C Palmitic Acid = 16C Oleic Acid = 18C Arachidonic Acid = 20C |
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Structure of TriacylGlycerols |
3 FA attached to a glycerol backbone When glycerol has different lengths FA at C1 C2 and C3 it is a chiral centre |
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Phospholipids |
2 Fatty acid chains to a glycerol backbone 3rd C on the glycerol is linked to a phosphate group thats modified by an alcohol Amphipathic: -Hydrophilic head due to charges on P group -Hydrophobic tails |
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Phospholipases |
Phospholipases A1 and A2 hydrolyse the ester bonds of intact glycerolphospholipids at C1 and C2 of glycerol When one of the FA has been removed by a type A phospholoiase the second is removed by a lysophospholipase Phospholipase C and D each split one of the phosphodiester bonds in the head group Some phospholipases act on only one type of glycerolphospholipid but some can be less specific |
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Structure of Cholesterol |
Polar head (OH) linked to 4 C rings labelled A-D from left to right From Ring D there is a Alkyl side chain For storage and transport the hydroxyl group condenses with a FA to form a sterol ester |
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Transport of Lipids |
Insoluble in water Transport system: -Non esterified FA: Free FA Albumin 2mM -Specific particles: Lipoproteins |
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Lipoproteins |
Particles with: -Core of hydrophobic lipids (TAGs or cholesteryl esters) -Coat of hydrophilid lipids ( phospholipids and cholesterols) -Protein: Apolilipoprotein (ApoB-100) The protein will protrude out of the surface |
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Apolipoprotein Functions |
Recognition: can bind to cell surface receptors Activators/Co-enzymes: Aid in lipoprotein metabolism ApoB48: Unique to chylomicrons -Comprised of only N terminus 48% of the protein encoded by ApoB gene -Glycosylated ApoB100: Found in VLDL and LDL -Synthesised in liver -Represents full-length protein encoded by APO B gene ApoCII: Activated lipoprotein lipases on tissue cells -Source is circulating HDL particles ApoE: Recognised by receptors on liver cells |
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Transport Proteins Pathways |
Exogenous Pathway: transports dietary lipids to peripheral tissues and liver Endogenous: Transports hepatic lipids to peripheral tissues Reverse Cholesterol Transport |
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Transport Proteins |
Lipids are transported in the blood as lipoproteins, there are many types Dietary lipids are packed in chylomicrons, much of their TAG content is released by lipoprotein lipase to adipose and muscle tissues during transport through capillaries Chylomicron reminants are taken up by the liver Endogenous lipids and cholesterol from the liver are delivered to adipose and muscle tisse by VLDL Extraction of lipid from VLDL gradually converts some of it to LDL, which delivers cholesterol to extra hepatic tissues or returns to the liver The liver takes up LDL, VDL remanats and chylomicrons by receptor mediated endocytosis Excess cholesterol is converted to bile salts |
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Exogenous Pathway |
Transport of dietary lipids from the intestine to the rest of the tissues Small Intestine: -Lipids emulsified -Monoacylglycerols, FA and cholesterol and lysophospholipids -Bile acids helps form micelles -Cross into enterocytes -Re-formation of phospholipids, TAG and cholesterol -These are assembled with ApoB48 onto chylomicrons |
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Lipoprotein Lipase |
Enzyme that metabolises chylomicrons in capillaries Homodimer Produced in adipose and muscle tissues, secreted and bound to surface of endothelial cells by heparan sulphate Activity stimulated by ApoCII The chylomicron remnant is removed by the liver |
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Conversion of VLDL to LDL |
VLDL particles secreted by hepatocytes acquire ApoE and ApoC Secreted VLDL will carry TAG to peripheral tissues VLDL metabolised by lipase in capillaries VLDL has half life of 4hrs VLDL remnants or intermediates density lipoprotein -Removed from circulation by liver -Transformed to LDL in blood |
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Endogenous Pathway |
Transport of lipids of hepatic origin to peripheral tissues Involves: -Assembly of VLDL -MTP -Assembly of LDL -LDL Pathway |
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MTP |
Microsomal tryglyceride transfer protein Promotes association of phospholipid, cholesterol ester and TAG with ApoB100 to form nascent VLDL Heterodimer Large subunit: Lipid transport Small subunit: Maintains structure Transcription of MTP gene increased by cholesterol Abetalipoproteinaemia: MTP abcent |
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Cholesterol Transport |
Only hepatocytes and enterocytes excrete cholesterol In the liver cholesterol is secreted into the bile Cholesterol from peripheral cells is transported to the liver and intestine by HDL |
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Atherosclerosis Stages |
1. Oxidised lipoproteins aggregation on extracellular matrix 2. Monocyte attracted 3. Monocyte into macrophage 4. Foam cell 5. Apoptosis 6. Cholesterol rich plaque forms Excess of cholesterols and LDL |
