Lipids and Related Systems PDF

Lipids and Related Systems Biochemistry, 8th Edition by Campbell and Farrell Biochemistry, 3rd Edition by Stoker Olivert M. Sitoy, M.Sc., R.Ch. Faculty, Chemistry Department College of Arts and Sciences Xavier University – Ateneo de Cagayan ...

Lipids and Related Systems Biochemistry, 8th Edition by Campbell and Farrell Biochemistry, 3rd Edition by Stoker Olivert M. Sitoy, M.Sc., R.Ch. Faculty, Chemistry Department College of Arts and Sciences Xavier University – Ateneo de Cagayan  Structure and Classification of Lipids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § An organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic solvents. § Unlike other biomolecules, lipids do not have a common structural features that serves as the basis for defining such compounds. § Classification: Based on two methods § Biochemical function § Saponification (hydrolysis under basic conditions)  Structure and Classification of Lipids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Classification based on Biochemical Function § For purposes of simplicity of study, lipids are divided into six categories based on their biochemical function: § Energy Storage Lipids: Triacylglycerols § Membrane Lipids: Phospholipids, Sphingoglycolipids, and Cholesterol § Emulsification Lipids: Bile Acids § Chemical Messenger Lipids: Steroid Hormones and Eicosanoids § Protecting-coating Lipids: Biological Waxes § Transport Lipids: Lipoproteins  Structure and Classification of Lipids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Classification based on Saponification § Saponification reaction: hydrolysis reaction that occurs in a basic solution. § Based on saponification reactions, lipids are divided into two categories: § Saponifiable lipids: triacylglycerols, phospholipids, sphingoglycolipids, cholesterol, and biological waxes § Non-saponifiable lipids: bile acids, steroid hormones, and eicosanoids  Structure and Classification of Lipids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Structure § Lipids exhibit structural diversity § Some are esters, some are amides, and some are alcohols (acyclic and cyclic) and some are polycyclic.  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Saturated and Unsaturated Fatty Acids § Carboxylic acids with linear (unbranched) carbon chains – Fatty acids are naturally occurring monocarboxylic acids § Even # of Carbon atoms: § Long chain fatty acids: C12 – C26 § Medium chain fatty acids: C6 – C11 § Short chain fatty acids: C4 – C5 § Two Types: § Saturated – All C-C bonds are single bonds § Unsaturated § Monosaturated: one C=C bond § Polyunsaturated: 2 or more C=C bonds present (up to six double bonds are present in fatty acids)  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Saturated Fatty Acids § Fatty acid with a carbon chain in which all C-C bonds are single bonds § Numbering starts from the end of –COOH group § Structural notation: indicates number of C atoms § Example – Lauric acid has 12 C atoms and no double bonds so it is (12:0)  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Unsaturated Fatty Acids § A monounsaturated fatty acid is a fatty acid with a carbon chain in which one carbon- carbon double bond is present. § Different ways of depicting the structure.  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Polyunsaturated Fatty Acids § A polyunsaturated fatty acid is a fatty acid with a carbon chain in which two or more carbon-carbon double bonds are present. § Up to six double bonds are found in biochemically important PUFAs. § Two types of unsaturated fatty acids. § Omega (ω)-3 fatty acids – An unsaturated fatty acid with its endmost double bond three carbons atoms away from its methyl end § Omega (ω)-6 fatty acids – An unsaturated fatty acid with its endmost double bond six carbons atoms away from its methyl end  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Polyunsaturated Fatty Acids § A polyunsaturated fatty acid is a fatty acid with a carbon chain in which two or more carbon-carbon double bonds are present. § Up to six double bonds are found in biochemically important PUFAs. § Two types of unsaturated fatty acids. § Omega (ω)-3 fatty acids – An unsaturated fatty acid with its endmost double bond three carbons atoms away from its methyl end § Omega (ω)-6 fatty acids – An unsaturated fatty acid with its endmost double bond six carbons atoms away from its methyl end  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Selected Unsaturated Fatty Acids of Biological Importance § Numbering starts from the other end of –COOH § Structural Notation: it indicates number of C atoms § E.g., 18:2 – 18 carbons, 2 double bonds  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Omega Acids § Essential Fatty Acids: Must be part of diet § Nutritionally important Omega-3 and Omega-6 fatty acids § Linolenic Acid – Omega-3 fatty acid § Linoleic Acid - Omega-6 fatty acid § Linoleic Acid Deficiency: § Skin redness – becomes irritated § Infections and dehydration § Liver Abnormalities § Children need it the most § Human milk has more than cow’s milk  Types of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § American Diet § Sufficient in omega 6 fatty acids § Deficient in omega 3 fatty acids § Fish – good source for omega 3 fatty acids § High rate of heart disease may be due to imbalance in omega 3 and 6 fatty acids § Ideal ratio: omega 6 : omega 3 (4-10 g: 1g)  Physical Properties of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Water Solubility: Short chain fatty acids have some solubility whereas long chain fatty acids are insoluble § Short chain fatty acids are sparingly soluble because of carboxylic acid polar group  Physical Properties of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § The Melting Point § The melting point depends upon: § Length of carbon chain § Degree of unsaturation (number of double bonds in a molecule)  Physical Properties of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Space-Filling Molecules § The number of bends in a fatty acid chain increase as the number of double increases § Less packing occurs § Melting point is lower § Tend to be liquid at room temperature  Physical Properties of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Physical Properties of Fatty Acids Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Energy-Storage Materials § With the notable exception of nerve cells, human cells store small amounts of energy providing materials: § The most widespread energy storage material – carbohydrate glycogen § Present in small amount § Major Energy – Storage material is triacylglycerols: § Triacylglycerols are concentrated primarily in special cells (adipocytes) § Adipocytes are nearly filled with triacylglycerols.  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Two Types of Triacylglycerols § Simple Triacylglycerols: Three identical fatty acids are esterified § Naturally occurring simple triacylglycerols are rare § Mixed Triacylglycerols: A triester formed from the esterification of glycerol with more than one kind of fatty acid § In In nature mostly mixed triacylglycerols are found and are different even from the same source depending on the feed, e.g., corn, peanut and wheat -fed cows have different triacylglycerols  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § Fats and Oils § Physical State: § Fats § Predominantly saturated § Solid or semisolids at room temperature § Oils: § Predominantly unsaturated § Liquids at room temperature § Source § Fats: Animal source and tasteless § Oils: Plants and Fish oil § Pure oils and fats are colorless, odorless  Energy-Storage Lipids: Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties.  Dietary Considerations and Triacylglycerols Lipids: heterogenous class of naturally occurring organic compounds on the basis of commonly solubility properties. § ”Good Fats” versus “Bad Fats” § Studies indicate that type of dietary fat and amount of dietary fat are important for a balanced diet: § Current recommended amounts are: total fat intake in calories: § 15% - Monounsaturated fat § 10% - Polyunsaturated §