10-Lipids Membranes

10-Lipids Membranes - Lipids and Cell Membranes Biological...

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Lipids and Cell Membranes Biological membranes: Structurally dynamic. Prevents molecules from passing across Contain transport systems (proteins) to enable selective permeability External cell membrane: plasma membrane Internal membrane in eukaryotic cells as boundaries for organelles Mitochondria, chloroplasts, peroxisomes, lysosomes, Golgi bodies, endoplasmic reticulum Information transduction, energy storage.
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Membrane Common Features Membranes are sheet-like structures: Two molecules thick 60~100Å thick (6-10 nm) Membranes contain mostly lipids and proteins 1:4 ~ 4:1 Membrane lipids are small molecules with hydrophilic and hydrophobic moieties. Membranes are noncovalent assemblies Membranes are fluid structures Specific proteins mediate distinctive functions in membranes. Membranes are asymmetric Membranes are electrically polarized (-60 mV in cell)
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Fatty Acids Fatty acids are the hydrophobic constituent of lipids Fatty acids: Hydrocarbon chains of various lengths and degrees of unsaturation that terminate with carboxylic acid groups Nomenclature: substitute -oic for -e of parent hydrocarbon Octadecanoic acid from octadecane (C 18 ) Palmitic acid: C 16 , saturated Oleic acid: C 18 , monounsaturated Numbering: from carboxyl terminus. Carbons 2 and 3 are the α and β carbons, respectively. The methyl carbon on the distal end is the ϖ carbon. Double bond is represented by followed by superscript number: cis- 9 : cis double bond between carbons 9 and 10. trans- 2 : trans double bond between carbons 2 and 3. Double bond position can be denoted by counting from the distal carbon with ϖ carbon as 1. Fatty acids are ionized at physiological pH, thus referred to as carboxylates such as palmitate. Even number of carbons: 14-24 with 16 and 18 most common. Unbranched in animals. Usually cis double bond. If multiple then separated by 1 methylene. Shorter chain length and higher unsaturation enhance fluidity of fatty acid containing membranes. Unsaturated fatty acids have lower melting points. Shorter fatty acids have lower melting points.
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Fatty Acids
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Lipids Lipids: water-insoluble biomolecules that are highly soluble in organic solvents such as chloroform (CHCl 3 ). Lipid function: Fuel Concentrated energy stores Signal molecule Membrane components Three types of membrane lipids Phospholipid Glycolipid cholesterol
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Phospholipids Phospholipid structure Fatty acid to provide hydrophobic component. Platform to which fatty acids are attached Glycerol sphingosine Phosphate Alcohol attached to phosphate Phosphoglycerides: phospholipids derived from glycerol Glycerol backbone with two fatty acid chains and a phosphorylated alcohol attached. Glycerol C1 and C2 hydroxyl groups esterified to carboxy groups of the two fatty acids.
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This note was uploaded on 11/10/2010 for the course CHE Biochem taught by Professor Disney during the Spring '10 term at SUNY Buffalo.

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10-Lipids Membranes - Lipids and Cell Membranes Biological...

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