Clinical Chemistry - Lipids and Lipoproteins Latest Update Graded A

Clinical Chemistry - Lipids and Lipoproteins Latest Update Graded A Roles of Lipids Rich source of energy and efficient way for body to store calories Fatty acids Linear chains of Carbon-Hydrogen bonds terminating in Carboxyl group Triglycerides Three fatty acids attached to One molecule of glycerol by ester bonds Lipoproteins Typically Spherical, composed of lipids and proteins, deliver fuel to peripheral cells Chylomicrons Largest and least dense Produced by intestine, deliver dietary liquids to hepatic and peripheral cells VLDL (Very Low Density Lipoproteins) Produced by liver, major carriers of endogenous triglycerides LDL (Low Density Lipoproteins) Form as a result of lipolysis of VLDL Readily taken up by cells via LDL receptors in Liver and peripheral cells, can infiltrate extracellular space HDL lipoprotein fraction Alpha LDL lipoprotein fraction Beta VLDL lipoprotein fraction Pre-Beta Phospholipids Similar to triglycerides, except with only Two esterified fatty acids Cholesterol Unsaturated steroid alcohol containing Four rings and Single side chain tail HDL (High Density Lipoproteins) Smallest and most dense Synthesized by Liver and Intestine Capable of removing excess cholesterol from peripheral cells Lipoprotein X Abnormal lipoprotein, patients with biliary cirrhosis or Cholestasis, LCAT mutations Lipoprotein Pathway #1 Lipid absorption - dietary lipids are converted to amphipathic lipids. Amphipathic lipids form micelles in intestinal lume Micelles come into contact with microvillus membranes if intestinal mucosal cells and are absorbed Lipoprotein Pathway #2 Exogenous pathway - Chylomicrons interact with proteoglycans on surface of capillaries in various tissues in circulation Free fatty acids & glycerol from hydrolysis of triglycerides by lipoprotein lipase can then be taken up Lipoprotein Pathway #3 Endogenous pathway - VLDL loses core lipids, causing dissociation and transfer of apolipoproteins & phosphsolipids to other lipoprotein particles. VLDL is converted to VLDL remnants, which get transformed by lypolysis into LDL Half of VLDL is converted to LDL, remainder is taken up as VLDL remnants by liver remnant receptors Lipoprotein Pathway #4 Reverse Cholesterol Transport Pathway - HDL removes excess cholesterol from cells Arteriosclerosis Single leading cause of death & disability in the US Caused by lipids, in form of esterified cholesterol being deposited in artery walls resulting in fatty streaks Hyperlipoprotinemia Diseases associated with elevated lipoprotein levels Hypercholesterolemia, Hypertriglyceridemia, and combined Hyperlipidemia Hypercholesterolemia Lipid abnormality most closely related to heart disease Familial hypercholesterolemia - genetic abnormality predisposing people to elevated cholesterol levels Homozygotes - rare 1:1 million - First heart attack in teens Heterozygotes - 1:500 more common Hypertriglyceridemia Elevated triglyceride levels: High 200-500 mg/dL Very High >500 mg/dL Genetic or hormonal abnormalities Combined Hyperlipoproteinemia Elevated level of serum cholesterol and triglycerides Increased risk