CHAPTER 10 (Pictures)

CHAPTER 10 (Pictures) - David L. Nelson and Michael M. Cox...

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1 Lehninger Principles of Biochemistry Fourth Edition Chapter 10: Lipids David L. Nelson and Michael M. Cox
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2 Introduction Lipids are: Extremely heterogeneous group of molecules They participate in a wide variety of cellular functions They are commonly insoluble in water Types of Lipids are: Storage lipids Examples: Fat and Oil Functions: stored form of energy Membrane lipids Examples: Phospholipids and sterol Functions: Structural element of biological membranes Other lipids Examples: Vitamins etc Functions: Enzyme cofactors, electron carriers, light absorbing pigment, hydrophobic anchors, emulsifying agents, hormones and intracellular messengers
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3 Storage Lipids-Fatty Acids Fat and Oil are derivatives of fatty acids Fatty acids are hydrocarbon (HC) derivatives Fatty Acids (FIGURE 11-1): Head Carboxylic acid Tail Hydrocarbon chain (4 to 36 ; C6 to C36) If the HC is alkane, the fatty acid is Saturated If the HC is alkene, the fatty acid is unsaturated The double bond of unsaturated fatty acid are indicated by the symbol n ; where 2200 = double bond N = location of d-bond with respect to carboxyl group
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5 Nomenclature of fatty acids (TABLE 11-1) Nomenclature of fatty acids (TABLE 11-1) 16:0 means 16-carbon saturated palmitic acid 18:1 ( 9) means 18-carbon oleic acid with one d-bond btw C-9 and C-10 What does 20:2 ( 9;12) mean? The d-bonds of polyunsaturated fatty acids are almost never conjugated but are separated by methylene group -CH=CH-CH=CH- almost NEVER -CH=CH- CH2 -CH=CH- always PRESENT
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7 Storage Lipids –Fatty Acid Cont. D-bonds may be either cis or trans in unsaturated fatty acids with cis isomers predominating. A cis d-bond puts a “kink” in the hydrocarbon chain Physical properties (Table 10-1) are determined by Length of chain Degree of unsaturation or branching of the hydrocarbon chain * Solubility (Table 10-1) Poor solubility in water because of nonpolar hydrocarbon chain (e.g., Lauric acid Mr 200 is soluble than glucose Mr 180) Longer chain and fewer d-bonds results in lower solubility Short chain fatty acid are slightly soluble because carboxyl acid gp is polar thereby ionizes at neutral pH
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8 Storage Lipids –Fatty Acid Cont. * Melting point (Table 10-1) Why are saturated FA 12:0 to 24:0 solid at RT whereas the unsaturated counterparts are oily liquids? Reason : The saturated FA can exist in extended conformations that can be tightly packed (strong van der Waals) in well- ordered crystals. Therefore, they have relatively high melting point (mp). FA with one or more
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CHAPTER 10 (Pictures) - David L. Nelson and Michael M. Cox...

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