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McMaster University
Hannah Holmes

BIOCHEM 3H03April 27 2014Lecture 23 Lipids Lipoproteins and Cardiovascular Disease Parts I and IIGENERAL NOTESFor this last section you really just need to focus on the tests and stuffA lot of the information at the first part of the section are just for background at least the first 10 slides are just to set the stage youre not going to be asked structures pathways details etc for the enzymesThere will be a lot of material but a lot of this is just setting the background for looking at lipids fats lipoproteins etc in the context of cardiovascular disease which is really important in terms of lab medicine and health care as a wholeEverybody knows this area its sort of generally recognized popular in general terms Dont want your cholesterol to go too high Bad cholesterolLDL good cholesterolHDL What kinds of fats are you supposed to avoidSaturated and trans unsaturated fatsReasons for these thingsdont need to know the mechanisms though At end of day were measuring blood samplesLDL cholesterol triglycerides For the most part trying to correlate the various disorders excardiovascular disease obesity diabetes etc Big picture Looking at results looking at presentation Gives us an opportunity to understand thisOVERVIEWClassificationBiological functionPhysiology metabolic and regulatory pathwaysPathology and diagnostic testing Assigned reading Chapter 14 in Marshallcovers the clinical part a lot of the structural part isnt in there but youre not required to know that anywayJust understand this first part you wont actually be tested on itLIPIDSgood to understand what fats and lipids areClassificationClassical definition o Any group of organic compounds including fats oils sterols and triglycerides or their derivatives that are insoluble in water and soluble in organic solventsBasically anything thats insoluble in waterTypes of lipidswe use a lot of these terms and its important to know what they mean o Fats a lot of times we use the word fats synonymously with cholesterol which is not exactly true so what are fats and what do they doTerm generally applied to storage lipids in animal tissueComprised of triglycerides and fatty acidsTypically talking about what occurs in animal tissues composed of fatty acids and triglyceridesSame idea with waxes and oilsWaxes solid at RT oils liquid at RTDifferent states of matter at different temperatures but same sort of structure essentially o Sterols A steroidbased alcohol such as cholesterol excholesterol backbonesTypesCholesterol Structure of cholesterol o Essential component of cell membranes o Precursor for steroid hormones bile acids Vitamin D etcForms a lot of the stuff we talked about in the endocrine unit o Fatty acids Composed of carboxylic acids with long hydrocarbon HC chainsIn general the fatty acids are used in terms of quick energy utilization alternative to glucose BIOCHEM 3H03April 27 2014 Length of hydrocarbon chain can vary from 1030 most common is 1218Shorter good for fuel longer good for storage in terms of fat triglycerides know they have different structuresShortchain fatty acids SCFA HC6C ie Butyric acidMediumchain fatty acids MCFA HC 612C ie Lauric acidLongchain fatty acids LCFA HC 1321C ie Oleic acidVery longchain fatty acids VLCFA HC 22C ie Cerotic acidSaturated no double bonds higher melting point at RT often found in animal fat you should avoid these in your dietStructurally they can pack MUCH more denselytightly hence more solid not the ONLY reason theyre not good for youthey are more prone to clotting issues and plaque development because they are more likely to solidify o Remember in CVD there are all sorts of variables and mechanisms exblood system heart lipoproteins etcUnsaturated have double bonds lower melting point at RT found in plants Tend to be more fluid dont lend themselves to packing as much because theyre bent o In atherosclerosis one factor affecting plaque formation is the tendency of the fatty acids to solidifyCis and Trans configurations with respect to double bonds avoid trans fatty acids because they are more rigid not all but some comparable to a linear chain cis configurations are more bento Bending is good because they cant pack densely cant turn into a solid as easily when you have an atherosclerotic plaque forming the solidification is a contributing factor o When you have a straight chain they can line up and pack densely and there is a greater chance of them solidifyingEssential fatty acids fatty acids that must be ingested because they cannot be synthesized o ExOmega3 and Omega6 are polyunsaturated fats often coming from fish oilbonds are all cis so they dont lend themselves well to packing linoleic acid omega3 fatty acid Linoleic acid omega6 fatty acid o Triglycerides an ester derived from glycerol and 3 fatty acidsGlycerol backbone with 3 fatty acids important for energy utilization in terms of storage analogous to glucose stored as glycogenFree fatty acids can be bound to albumin for example to be transported in blood but triglyceride structure is good for storage in terms of fat storage in adipose tissues can be broken down very quicklyNot soluble on their own so they need to be transported cant transport triglycerides freeFree fatty acids can be transported on their own to a certain degree but are usually bound to albumin o Phospholipid variation on same theme comprised of diglyceride phosphate group and a simple organic moleculeMost often composed ofA diglyceride moleculePhosphate group An organic molecule excholineFunction form cell membranes signalling moleculesMajor component of cell membranesAlso important for cell signalling pathways All of these are fairly similar with the fatty acid chains except cholesterol
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