Week 8 Biochem Lec LIPIDS PDF

College of Medical Laboratory Science WEEK 8 BIOCHEM LEC: LIPIDS Trixie Anne R. Molina RMT, MLS(ASCPi)cm [email protected] LEARNING OBJECTIVES h At the end of the learning session, the students must be able to: u.p.ed Define a...

College of Medical Laboratory Science WEEK 8 BIOCHEM LEC: LIPIDS Trixie Anne R. Molina RMT, MLS(ASCPi)cm [email protected] LEARNING OBJECTIVES h At the end of the learning session, the students must be able to: u.p.ed Define accurately the terms associated with lipids ma ti Discuss extensively the classifications of lipids a f and related compounds and give examples of @ each. lina o Enumerate exactly the different functions of rm lipids and other compounds related to it. t CHARACTERISTICS OF LIPIDS An organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic solvents. Lipids do not have a common structural features that serves as the basis for h defining such compounds. u.p Lipids are present in humans, animals, plants and micro-organisms to some extent..ed a Also serve as a source of energy m ati Fat is an ideal form for storing energy in the human body compared to @f carbohydrates and proteins ina A lipid is a fat-like substance but need not be a fatty acid always. l o Classification: They are classified on the basis of solubility not on any functional m groups tr CHARACTERISTICS OF LIPIDS Lipid molecules often combine covalently to other biomolecules to form hybrid biomolecules such as glycolipids and lipoproteins. Disturbances in lipid metabolism are known to accompany a variety of disease states, especially heart disease and obesity. p Lipids exhibit structural diversity. h u Some are esters, some are amides, and some are alcohols (acyclic and cyclic) d and some are polycyclic. a.e CHEMICAL NATURE OF LIPIDS tim fa a @ Lipids are the group of greasy organic compounds, which are soluble in organic solvents o lin m Insoluble in water t r They are fats, waxes, compound lipids, steroids, fatty acids and fat soluble vitamins. FUNCTION OF LIPIDS Energy-storage lipids Membrane lipids.ph Emulsification lipids du Chemical messenger lipids a.e Protective-coating lipids tim f a a @ o lin trm CLASSIFICATION OF LIPIDS -BASED ON THE COMPOSITION Simple lipids Compound lipids Derived lipids.ph Simple lipids d u.e An ester is formed when acid reacts a They are esters of fatty acids with alcohols. t im with alcohol Fats f a a @ o Structure: li n Esters of fatty acids with glycerol consist of three molecules of fatty acids t r m esterified with one molecule of glycerol All the three fatty acids can be same or different. SIMPLE LIPIDS - FATS Nomenclature of Triglycerides The carbon atoms of glycerol of triglycerides are indicated with both Indo-Arabic numbers and Greek alphabets p h The triglycerides are further subdivided based on type of fatty. acids esterified to glycerol. d u Simple Triglyceride a.e t im a Mixed Triglyceride @ f Simple Triglyceride lin a m o All the three fatty acids esterifed to glycerol are same tr Mixed triglyceride All the three fatty acids esterified to glycerol are different OTHER NOTEWORTHY ACYL GLYCEROLS Diacylglycerol 2 fatty acids are esterified to glycerol 1,2-diacyglycerol and 1,3-diacylglycerol. In 1,2-. ph diacylglycerol, the 1st and 2nd–OH groups are esterified One fatty acid is esterified with glycerol..ed Monoacylglycerol u m a 1-monoacylglycerol and ti 2-monoacylglycerol. a group is esterified. In 1- @ monoacylglycerol the 1st —OHf li n a m o t r SIMPLE LIPIDS - FATS Functions of Triglycerides Storage lipids in animals and in plants. Fat stored under the skin serve as energy store and as insulator against cold..p h d u e Functions of Partial Acylglycerols Found in some tissues a. ti m f a Mainly they are formed as intermediates during the synthesis a @ of triglycerides and during digestion of fat. o lin t rm SIMPLE LIPIDS - FATS PHYSICAL PROPERTIES OF TRIGLYCERIDES Pure fats have no colour, taste and odour. At room temperature, fats of plant origin remains oil Triglycerides containing asymmetric carbon.ph atom are optically active. d u a.e m CHEMICAL PROPERTIES OF FATS a t i f Saponification a When fats are boiled@ with bases like KOH or NaOH glycerol o lin and salts of fatty acids are formed tr m Hydrogenation It converts unsaturated fatty acids of triglycerides into saturated fatty acids. SIMPLE LIPIDS - FATS CHEMICAL PROPERTIES OF FATS Hydrogenation Hardening Lipid Peroxidation.p h Rancidity du a.e Atmospheric oxygen reacts with unsaturated fattly acids of t im triglycerides and forms lipid peroxides. fa a @ o lin t rm SIMPLE LIPIDS - WAXES Waxes Esters of fatty acids with long chain alcohol. E.g Lanolin or wool fat.p h Cholesterol ester d u Bees wax a.e Serve as protective coatingstion mskin, fur and feathers of fa a @ animals, birds and on fruit and leaves of plants Water barrier forin o l animals, birds and insects. Further wax is hard r m in cold climate and soft in hot climate. t organisms use wax as source of energy. Marine COMPOUND LIPIDS COMPOUND LIPIDS Esters of fatty acids with alcohol containing nitrogenous bases and additional groups..p h d u Based on alcohol compounds lipids are subdivided into: Glycerophospholipids a. e Sphingo lipids t im fadivided into phospholipids and @ Compounds lipids are also glycolipids. lin a m o t r COMPOUND LIPIDS - GLYCEROPHOSPHOLIPIDS OR PHOSPHOLIPIDS GLYCEROPHOSPHOLIPIDS OR PHOSPHOLIPIDS They contain two molecules of fatty acids esterified to first and second hydroxyl groups of glycerol. p h The third hydroxyl group of glycerol is esterified to phosphoric acid Further a nitrogen base or second alcohol is also.esterified d u to phosphoric acid a.e tim Glycerophospholipid without second alcohol is known as phosphatidic fa @ acid. in a Some glycerophospholipids l are named according to second alcohol or o acid trm nitrogen base and they are considered as derivatives of phosphatidic COMPOUND LIPIDS - GLYCEROPHOSPHOLIPIDS OR PHOSPHOLIPIDS Phosphatidylcholine It contains two fatty acids esterified to first and second hydroxyl group of glycerol. The third hydroxyl is esterified to phosphoric acid to which second alcohol choline is also esterified. Contains a saturated fatty acid at C-1 position and unsaturated fatty acid at C-2 position..ph Major phospholipid of cell membrane. Phosphotidyl ethanolamine du.e In which second alcohol ethanolamine is esterified to phosphoric acid of phosphatidic acid a im Phosphatidyl serine fat In which aminoacid serine is esterified to phosphoric acid of phosphatidic acid. a@ Phosphatidyl Inositol lin In which polyol inositol is esterified to phosphoric acid of phosphatidic acid. o m Further phosphorylated phosphatidyl inositol (PIP2) and inositol triphosphate (IP3) are tr involved in signal transduction. COMPOUND LIPIDS Other Noteworthy Phospholipids Dipalmitoyl Lecithin Two molecules of palmitic acid are esterified to 1st and 2nd carbon atoms of glycerol. A phosphocoline is esterified to the third hydroxyl group..ph It is secreted in alveoli of lungs. du Acts as surfactant in the lungs Cardiolipin a.e im It is a double glycerophospholipid. It contains two phosphatidic acids esterified o C- t fa and C-3 of glycerol. a@ It has immunological properties and used in the diagnosis of syphilis. lin Lysophospholipids o m They are derivatives of glycerophospholipids. They contain only one acyl group instead tr of two acyl groups. Component of cobra venom and a strong hemolysing agent. COMPOUND LIPIDS - SPHINGOLIPIDS Other Noteworthy Phospholipids Plasmalogens They are also glycero phospholipids These compounds contain unsaturated fatty alcohol in place of fatty acid at the C-1 position. Hence, the normal ester linkage. p h [email protected] is replaced by ether linkage on the C-1 carbon d u of glycerol. Usually nitrogen bases are choline, serine and ethanolamine Content is more in cancer cells a.e SPHINGOLIPIDS tim fachain amino alcohol sphingosine and bases @ They contain fatty acid long or additional groups.a o lin tr m They are subdivided Sphingomyelins into: Glycolipids COMPOUND LIPIDS - SPHINGOLIPIDS SPHINGOMYELINS Fatty acid is linked to sphingosine by an amide bond and phosphorylcholine is esterified to C-1 hydroxyl of sphingosine. They are simple and most abundant sphingolipids..ph They are present in most of animal membranes. u Myelin sheath of nerve cells is rich in sphingomyelins..ed Grey matter also contain sphingomyelins. ma GLYCOLIPIDS ati @f They are subdivided into: ina Cerebrosides l o Gangliosides m tr COMPOUND LIPIDS - SPHINGOLIPIDS Cerebrosides Contain sphingosine, fatty acid and sugar. The combination of sphingosine and fatty acid is called as ceramide. Cerebrosides differ in the type of sugar, usually they are named according to the.p h u sugar present.. e In some cerebrosides, sulfate is attached to sugar d then they are called as sulfatides or sulfolipid m a a t i f Cerebrosides occur in large amounts in white matter of brain and in myelin sheath of nerves. Some cerebrosides area @ o l in present in non-neural tissue. tr m COMPOUND LIPIDS -SPHINGOLIPIDS GANGLIOSIDES Highly complex sphingolipids. They contain ceramide, oligosaccharide and sialic acid. They are abundant in grey matter of brain..p h u They are also found in non-nerval tissues. They are components of hormone receptors..e d m a They also function as receptors for toxins of cholera, influenza and tetanus. a t i f They are also involved in cell-cell recognition, growth, differentiation and carcinogenesis. a @ o lin t r m DERIVED LIPIDS - FATTY ACIDS They are acids derived from fats. They are monocarboxylic acids containing long hydro carbon side chain. Based on the nature of hydrocarbon side chain, they are divided into: h Saturated fatty acids u.p Unsaturated fatty acids - Monounsaturated or Polyunsaturated.e d Fatty acids are also divided based on hydrocarbon chain length. They are: Short chain fatty acids m a a t i f Medium chain fatty acids Long chain fatty acids a @ lin Very long chain fatty o acids tr m DERIVED LIPIDS - FATTY ACIDS Cis-trans isomerism Unsaturated fatty acids exhibit cis-trans isomerism In the cis-isomer bulky groups are located on the same side of double p h bond where as in trans isomer they are on the opposite side of double. bond d u a.e Cis and trans isomers are not interchangeable in cells. Only cis isomers t im a can fit into cell membrane because of bend at double bond. @ f lina m o t r DERIVED LIPIDS - FATTY ACIDS Nomenclature of Fatty Acids Saturated fatty acids Have both trivial names and systematic names Systematic name.ph Consist of two parts: du Name of hydrocarbon chain forms first part. ‘oic’ substituted in place of a.e ‘e’ of hydrocarbon name forms second part tim Usually saturated fatty acids end as anoic acids. fa Example: a@ lin Systematic name for a saturated fatty acid containing 8 carbon atoms o m (octane+ oic + acid) —→ octanoic acid tr Trivial name: caprylic acid DERIVED LIPIDS - FATTY ACIDS.ph du a.e tim fa a@ olin trm DERIVED LIPIDS - FATTY ACIDS Nomenclature of Fatty Acids Unsaturated fatty acids Trivial names, systematic names, -end names and shorthand forms. Systematic name ph The name of hydrocarbon forms first part of systematic name of unsaturated fatty. u acids. But ‘enoic’ substituted in place of ‘ne’ of name of hydrocarbon forms second d.e part. Number of double bonds are written before ‘enoic’ and symbol showing a m position of double bonds and isomerism around double bond are written between ati two parts or in the beginning. @f a Example: olin Mono unsaturated fatty acid palmitoleic acid (trivial name) containing 16 carbon atoms rm and one double bond between 9 and 10 carbon atoms t (Hexadecane + Δ9-cis-mono+enoic+acid) —→ cis-9-Hexadecaenoic acid DERIVED LIPIDS - FATTY ACIDS Nomenclature of Fatty Acids Unsaturated fatty acids Trivial names, systematic names, -end names and shorthand forms. Systematic name.p h The name of hydrocarbon forms first part of systematic name of d u e unsaturated fatty acids. But ‘enoic’ substituted in place of ‘ne’ of name of hydrocarbon forms second part. a. Number of double bonds are m written before ‘enoic’ andisymbol t adouble bond are written between two parts or in showing position of double bonds @ and isomerism aroundf lin a the beginning. m o tr DERIVED LIPIDS - FATTY ACIDS.ph du a.e tim fa a@ olin trm DERIVED LIPIDS - FATTY ACIDS ESSENTIAL FATTY ACIDS Not systhesized in the body. PUFA They are linoleic acid (LA), linolenic acid (LNA) and arachidonic acid (AA)..ph Nutritionally important Omega-3 and Omega-6 fatty acids d u e Linolenic acid – Omega-3 Linoleic acid – Omega-6 a. m They are essential for the synthesis ofieicosanoids. t fa lipids. @ They are also required for membrane a o lin t r m DERIVED LIPIDS - STEROIDS STEROIDS Complex molecules containing four fused rings. The four fused rings makeup ‘cyclopentanoperhydrophenanthrene’ Most abundant steroids are sterols which are steroid alcohols..p h Steroids are called as non-saponifiable lipids because they contain no fatty acids and they can not form soaps. d u CHOLESTEROL a. e t im In animal tissue, cholesterol is the major sterol 3-hydroxy-5,6-cholestene a @ f Found in bile lin a m o Important components of cell membrane and lipoproteins. r D tVitamin Steroids with diverse physiological functions are derived from cholesterol. Bile Acids DERIVED LIPIDS - STEROIDS Steroids with diverse physiological functions are derived from cholesterol. Hormones of adrenal cortex Female sex hormones Male sex hormones Other Noteworthy Steroids.p h d u.e Ergosterol Provitamin of vitamin D found in yeast and plants. Sitosterol Present in plants. Cardiac glycosides like ouabain andim a f t a from cholesterol. streptomycin an antibiotic. @ Coprostanol found in feces is derived a lin Wool fat sterols like agnosterol o and lanosterol. tr m CLASSIFICATION OF LIPIDS -ACCORDING TO THEIR INTERACTION WITH WATER Polar lipids Non-polar lipids Polar lipids They are further sub-divided into 3 sub-classes Class one polar lipids.ph u Non-swelling water insoluble amphipathic molecules (Amphiphiles) which forms thin lipid mono d layer in water. Class two polar lipids a.e tim welling and water insoluble amphiphiles which forms stable lipid monolayer as well as laminated fa lipid water structure known as liquid crystals. a@ Class three polar lipids lin Water soluble amphiphiles, which contain strong polar head groups. These are water soluble only at o low concentrations. trm Non-polar Lipids Insoluble in water Cholesterol esters, carotenes and hydrocarbons EICOSANOIDS Derived from eicosapolyenoic fatty acid like arachidonic acid. They are prostanoids, leukotrines (LTA) and lipoxins (LX). The prostanoids include prostaglandins (PG), prostacyclins (PGI) and thromboxanes (TXA). Often word prostaglandins is used to indicate all prostanoids. Prostaglandins.ph du Chemically prostaglandins are derivatives of a 20 carbon prostanoic acid. a.e Prostanoic acid is a cyclic compound with two side chains. tim The cyclic ring present in prostanoic acid is a cyclopentane ring. fa There are some six or more types of prostaglandins. a@ They differ in the substituents on the cyclopentane ring. Prostacylins olin trm Contain a second five-numbered ring in addition to the one common to all prostaglandins Thromboxane Identified first in thrombocytes Contain a six numbered heterocyclic oxane ring EICOSANOIDS Leukotriens and Lipoxins Found in leukocytes They are derivatives of arachidonic acid and contain no cyclic ring. FUNCTIONS OF EICOSANOIDS.ph du Function as local hormones. a.e They act on several organs and produce physiological as well as pharmacological effects. tim fa a@ olin trm LIPOPROTEINS Lipid protein complexes found in plasma. They are non-covalent assemblies The protein part of lipoprotein is called as apolipoprotein or apoprotein. Structure consist of non-polar lipid core surrounded by apoproteins and more polar lipids Classification of Lipoproteins.ph Based on their density du Chylomicrons a.e im Very low density liporoteins t fa Low density liporoteins a@ High density lipoproteins lin Based on differences in electrophoretic mobilities o m a-lipoproteins tr pre-B-lipoproteins B-lipoproteins chylomicrons LIPOPROTEINS Composition of Lipoproteins Lipids of lipoproteins Lipid constituents of lipoproteins are mostly triglycerides, free and esterified cholesterol and phospholipids h The proportion of triglycerides, cholesterol and phospholipids differs in various lipoproteins u.p.ed ma ati @f lina mo tr LIPOPROTEINS Apoproteins of lipoproteins The proportion of protein part differs in various lipoproteins The composition of apoprotein part also differs among various lipoproteins. There are five types of apoproteins. h Some of the apoproteins have subtypes. Apo-B u.p.ed It is a glycoprotein contains sialic acid, mannose, glucose, galactose and fructose. a Other little known apoproteins are apo F, apo G and apo H. t Functions of Lipoproteins im fa Involved in the transportation of lipids in the body. @ Other Noteworthy Functions of Lipoproteins a lin Important for synthesis and degradation of lipoproteins o Activators/inhibitors of some enzymes associated with lipid metabolism trm LIPOPROTEINS Lipoprotein X(LpX) It is a variant of LDL. Bilammallar vesicle with an aqueous lumen. It contains equal amounts o phospholipids and cholesterol. Triglycerides and cholesterol esters are present in only small amounts.ph du Appears in the plasma of cholestatic patients. It may be formed in bile and enters a.e plasma due to regurgitation that occurs in cholestatic individuals. tim fa a@ olin trm REFERENCES Rao, M.N. Medical Biochemistry, 2nd edition, New Age International Publishers, 2006 Stoker, H. S, General, Organic and Biological Chemistry. 5th Edition  College of Medical Laboratory Science QUESTIONS? Trixie Anne R. Molina RMT, MLS(ASCPi)cm  College of Medical Laboratory Science THANK YOU SO MU- Trixie Anne R. Molina RMT, MLS(ASCPi)cm