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Lecture 9-30 - Lecture 9-30 Ch 8 DONT HAVE TO MEMORIZE...

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Lecture 9-30: Ch. 8 DON’T HAVE TO MEMORIZE FATTY ACIDS!!! MEMBRANES and LIPIDS This is a functional rather than structural definition: A lipid is a substance that can be extracted from a cells with a nonpolar solvent (chloroform, ether, acetone) and does not dissolve in water to any appreciable extent. Functions structural components of membranes-separate cells from environment; separate internal components: mitochondria, nucleus storage and transport of energy protective functions--waterproofing regulators--hormones (steroids) precursors--vitamins (A,D,E,K) Classes of lipids fatty acids and derivatives triacylglycerols wax esters phospholipids: glycerophospholipids or phosphoglycerides sphingolipids isoprenoids--built from 5 carbon units--eg. cholesterol, ubiquinone, fat soluble vitamins sterols--derivatives of cholesterol, hormones FATTY ACIDS (FAs) monocarboxylic acids-hydrogen chains of varying length pKa about 4.5-- so at physiological pH the carboxyl is in the ionized form (COO-) amphipathic molecules--both hydrophobic and hydrophilic character most FAs have an even number of carbons in an unbranched chain branched or cyclic FAs occur in some species (mostly bacteria) FAs can be unsaturated at one or more C-C single bonds The common saturated fatty acids: Caprate-10 Cs; 10:0----The first number is the number of carbons and the 0 indicates no double bonds Laurate-12 Cs; 12:0 Myristate-14 Cs; 14:0
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Palmitate-16 Cs, 16:0 Stearate-18 Cs; 18:0 Arachinate-20 Cs; 20:0 Behenate-22 Cs; 22:0 Lignocerate-24 Cs:24:0 Cerotate-26 Cs; 26:0 Palmitoleate-16:1cD9 Oleate-18:1cD9 Linolate-18:2cD9,12 Linolenate-18:3cD9,12,15 Arachidnate-20:4cD5,8,11,14 Unstaturated Fatty acids FA can be unsaturated--contain one or more double bonds double bond allows for cis/trans isomers cis-isomer: R groups are on the same side-places a "kink" in the chain; cannot pack as closely, lowers the melting point trans-isomer: R groups are on the opposite side--structure more similar to saturated FAs-- trans FA and heart disease ( bad because they aren’t natural) most naturally occurring FAs are in the cis conformation Oleate and linolate are the most abundant FAs in all organisms Plants and bacteria synthesize FAs from acetyl-CoA Animals obtain most FAs from diet essential FAs, linolate and linolenate cannot be synthesized by animals necessary for membranes and precursors of important metabolites, e.g. linolenate is the precursor for arachidonate which is the precursor for prostaglandins animals can synthesize some FAs and modify some FAs are also found in proteins myristate and palmitate are found covalently linked to proteins--"acylated" proteins the presence of these groups facilitate interactions with membranes--provide some "hydrophobicity" to the protein o help a protein stay in a membrane--lipid anchored TRIACYLGLYCEROLS (TAGs): FATS AND OILS TAGS are used to store of energy, fully reduced carbon yields maximum energy when oxidized Triesters of FAs and glycerol Oils are liquid at RT--less saturated fatty acids Fats are solid at RT--more saturated fatty acids
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