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BIOC12Fall2012 Lecture Week 9 Notes

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University of Toronto Scarborough
Biological Sciences
Rongmin Zhao

BIOC12Fall2012 Lecture 9 Lipids membranes and membrane proteins Chapter 8 and Chapter 9o Topologyhow proteins are linked to the membrane Lipid Functions o Lipids are essential components of all living organisms o Much greater variation than protein and carbohydrates o Water insoluble anda re highly soluble in non polar solvents o They can be strictly hydrophobic small number not usually biological or more often amphipathic with both polar and nonpolar regionso There are 3 classes of function 1 form lipid bilayers one memberane 2 Contain hydrocarbon chains as energy stores long term 3 Intra or intercellular communication Classes of lipids o Almost all biological lipids are amphipathic o Fatty acids which are the simplest and jave a general formula of RCOOH where R is a hydrocarbon chain o More complex lipids that can have fatty acids as components o Triacylglycerols fats and oil function as storage molecules for metabolic energy and provide thermal insulation and padding o Glycerophospholipids membrane component most abundanto Sphingolipids membrane componenet abundant in the braino Isoprene based 5 carbon lipidsincludes steroids lipid vitamins and terpenescalled isoprenoids steroid hormones have a role in regulation membrane componeneto Waxes esters of long chain alcohols with long chain fatty acidsin cell walls exoskeleton and skin serve a protective role o The structure is similar to detergentwhen dissolved it could form a micelle oo saturated hydrocarbon chain only contains single bonds o unsaturatedthere is at least one double bondo the lower the number of double bonds the lower the melting pointo example cooking oil is found in liquit form at room temperature unsaturated o namingexample lauric acid is common name dodecanoic acid is systematic name symbol is 120this means there at 12 total carbon and 0 double bondsStructural Consequences of Unsaturationo saturated chains pack tihglty and form more rigid organized aggregates ie membranes therefore solids at room temperature o unsaturated chains bend and pack in a less ordered way with greater potential for motionproduce flesxible fluid aggregates therefore liquid at room temperatureo the length of the tail and degree of unsaturation affect the melting point The Structures and Chemistry of Triacylglycerolo most of the fatty acids in plants and animals exist in the form of triacylglyceros o if all 3 fatty acids are the same the molecule is called a simple triacylglycerol o they are form from 1 glycerol3 fatty acids oo mixed triacylglycerols contain 2 or 3 different fatty acids Glycerophospholipids oo the most abundant lipid in biological membranes o has a glucerol backbone like a triacylglycerol o simplest example is phosphatidates which consists of 2 fatty acyl groups esterified to C1 and C2 of glycerol 3phosphate in which the C3 glycerol has a phosphate group o each type of glycerophospholipid consists of a group of molecules with the same polar head and different fatty acyl chainso phospholipases serve as effetors in signal transduction to produce phospholipid based second messengers can be used to determine the structure and identities of individual fatty acids o venom from snakes is made up of enzymes which can break down the lipid bilayercauses cells to lysedeath
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