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LEHNINGER PRINCIPLES OF BIOCHEMISTRY
David L. Nelson and Michael M. Cox LEHNINGER PRINCIPLES OF BIOCHEMISTRY Sixth Edition CHAPTER 10 Lipids © 2013 W. H. Freeman and Company
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Lipids Lipids are a family of compounds that are
relatively insoluble in water. Lipids play major roles in: energy storage membrane structure Other roles of lipids: enzyme cofactors light-absorbing pigments hormones signal transduction molecules
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Lipids often contain fatty acids molecules.
Fatty acids are carboxylic acids with hydrocarbon chains from 4 to 36 carbons long. The most common biological fatty acids have an even number of carbons between 12 and 24 carbons. Fatty acids can be saturated (no double bonds) or unsaturated (containing double bonds) double bonds are in the cis configuration. Nomenclature: 16:0 is a 16 carbon fatty acid with no double bonds 20:2 (D9,12) is a 20 carbon fatty acid with double bonds after C-9 and C-12 (C-1 is COOH)
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Packing of fatty acids into stable aggregates
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Triacylglycerols contain three fatty acids esterified to a glycerol backbone
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Triacylglycerols are stored energy in fat cells and plant seeds
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The greater the percentage of saturated fatty acids in food fats the higher the melting temperature
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Waxes are esters of long chain fatty acids
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Common types of storage and membrane lipids
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Glycerophospholipids, the main lipid component of biological membranes, contain two fatty acids esterified to a glycerol phosphate backbone
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Structure of phosphatidylcholine
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Glycerophospholipids with ether-linked fatty acids
Abundant in the heart Important in inflammatory response
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Archaea contain unique membrane lipids
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Sphingomyelin is similar in structure to phosphatidylcholine
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Glycosphingolipids as determinants of blood groups
Glycosphingolipids contain the blood group antigens present on the surface of red blood cells
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Blood Groups The carbohydrates on certain sphingolipids determine
your blood group, affecting the blood type you can receive in a transfusion. These sphingolipids are on the surface of erythrocytes. Type A individual has A antigens and anti-B antibodies Type B individual has B antigens and anti-A antibodies Type AB individual has A and B antigens and neither anti-A nor anti-B antibodies Type O individual has O antigen and both anti-A and anti-B antibodies Example: Type A individual cannot receive Type B blood. Antigen-antibody interaction causes agglutination
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The specificities of phospholipases, enzymes that cleave glycerophospholipids
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Sterols have four fused carbon rings Cholesterol is the main sterol in animal tissues
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Bile acids are synthesized from cholesterol Bile acids aid in emulsification of dietary fat in the intestine
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Arachidonate is the precursor for eicosanoid hormones Eicosanoids are involved in pain, fever, inflammation
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Other sterols are synthesized from cholesterol
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Vitamin D is produced in the skin by UV irradiation of 7-dehydrocholestreol
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Vitamin A is a lipid belonging to the isoprenoid family
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Some biologically important isoprenoids
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