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Chapter 10.1: Storage Lipids

Chapter 10.1: Storage Lipids. CHEM 7784 Biochemistry Professor Bensley. CHAPTER 10.1 Storage Lipids. Biological roles of lipids Structure and properties of storage lipids. Chapter Objectives : To understand the. Low solubility in water Good solubility in nonpolar solvents.

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Chapter 10.1: Storage Lipids

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  1. Chapter 10.1: Storage Lipids CHEM 7784 Biochemistry Professor Bensley

  2. CHAPTER 10.1 Storage Lipids • Biological roles of lipids • Structure and properties of storage lipids Chapter Objectives: To understand the

  3. Low solubility in water Good solubility in nonpolar solvents Lipids: Structurally Diverse Class

  4. Classification of Lipids • Based on the structure and function: • Lipids that contain fatty acids (complex lipids): • Storage lipids and membrane lipids • Lipids that do not contain fatty acids: • Cholesterol, terpenes, …

  5. Lipid Subclasses

  6. Fatty Acids • Carboxylic acids with hydrocarbon chains containing from 4 to 36 carbons • Almost all natural fatty acids have an even number of carbons • Most natural fatty acids are unbranched • Saturated: • Monounsaturated: • Polyunsaturated:

  7. Common Saturated Fatty Acids

  8. Common Unsaturated Fatty Acids

  9. Physical Properties and Conformation of Saturated Fatty Acids • Solubility decreases as the chain length increases • Melting point increases as the chain length increases • The saturated chain tends to adopt extended conformations • The double bonds in natural unsaturated fatty acids are commonly in cis configuration • This introduces a kink in the chain

  10. Melting Point and Double Bonds • Saturated fatty acids pack in a fairly orderly way • extensive favorable interactions • Unsaturated cis fatty acid pack less regular due to the kink • Less extensive favorable interactions • It takes less thermal energy to disrupt disordered packing of unsaturated fatty acids: • unsaturated cis fatty acids have a lower melting point

  11. 18:0 18:1 18:3 70o C 13o C -17o C Melting Points of Fatty Acids

  12. Trans Fatty Acids • Trans fatty acids form by partial dehydrogenation of unsaturated fatty acids • A trans double bond allows a given fatty acid to adopt an extended conformation • Trans fatty acids can pack more regularly, and show higher melting points than cis forms

  13. Triacylglycerols (fats and oils) • Majority of fatty acids in biological systems are found in the form of triacylglycerols • Triacylglycerols are the primary storage form of lipids (body fat) • Triacylglycerols are less soluble in water than fatty acids due to the lack of charged carboxylate group • Triacylglycerols are less dense than water: fats and oils float

  14. Waxes • Waxes are esters of long-chain saturated and unsaturated fatty acids with long-chain alcohols • Insoluble and have high melting points • Beeswax is a mixture of a large number of lipids, including esters of triacontanol, and a long-chain alkane hentiacontane

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