Exam 1 Review:Lipids: hydrophobic/nonpolar Omega 3 and omega 6 = essential, from diet The longer the chain, the higher the melting point Stearic acid = 18:0 = solid at room temperature Adding double bonds decreases melting pointMost of the fatty acid in the body is esterified: fatty acids are attached to glycerol First strand of fatty acid is straight, no kinks Other 2 strands are kinked = cis-fatty acid Kinks = good for membranes because they require less packing = more fluid Trans = bad because no kinks and pack tightly Phospholipids: glycerol, 2 fatty acids, phosphate + X (polar head group) o 1 saturated fatty acid chaino 1 unsaturated fatty acid chainCholesterol: synthesized from Acetyl CoA, requires lots of NADPH - Added to membranes to keep membrane fluid - Transports triglycerides in the blood by VLDLPlasma Membrane:- Integral proteins span the membrane - Glycolipids on the outside of membrane- Specialized microdomains Beta Oxidation: breaking down fatty acids- Fatty acids are carried to cells on albumin- When it comes into the cell, it enters the cytosol, and it is activated by being put on Coenzyme A by thiokinase- Carnitine pulls this fatty acid from cytosol into mitochondria- When fatty acid is in the mitochondria, the beta carbon is oxidized (remove hydrogens, put them on FAD, add a water, remove 2 more hydrogens, put them on NADH) - Carnitine is taken off and taken back out of mitochondriaOxidation of Palmitic Acid: 16 carbons = 8 2C acetyl coA units- 7 turns of beta oxidation cycleEnergy yield for Fatty acid oxidation = # beta oxidation cycles x 5 FA activation – 2ATP For full oxidation: + # acetyl coA x 12 = energy yield from full oxidation OXIDATION = mitochondria, carbons removed 2 at a time, coenzymes = FAD & NAD+SYNTHESIS: cytosol, carbon atoms added 2 at a time, coenzyme = NADPH Fatty Acid Synthesis: when insulin is present» Acetyl coA carboxylase is rate limiting control point »Fatty acid synthesis stops at 16C or 18CAdding double bonds with desaturates can reach 9C from COOH end Cholesterol is made from acetyl coA and uses lots of NADP» HMG-CoA reductase is rate limiting enzyme Chylomicrons & VLDL = triglyceride transportLipoprotein lipase hydrolyzes triglycerides so they can move to tissues Remainder of VLDL processed to 2 forms = LDL and HDL (which only deal with cholesterol)LDL: makes cholesterol available to cells of the body = BAD = deposited in arteries (most cholesterol in the body) HDL: picks up excess cholesterol, returns to liver = GOODCholesterol in the Liver: o Liver has receptors for LDL, HDL, VLDL remnant o Statins inhibit synthesis of cholesterol Digestion & Absorption of Dietary Lipids:o Hormone sensitive lipase activated by glucagon
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