Lipids PDF

LIPIDS Fatty Acids, Glycerol, Steroids, Fatty Heterogenous group of compounds aldehydes, Ketone bodies, Fats, Oils, Steroid, Waxes Hydrocarbons, Lipid – soluble Insoluble in wat...

LIPIDS Fatty Acids, Glycerol, Steroids, Fatty Heterogenous group of compounds aldehydes, Ketone bodies, Fats, Oils, Steroid, Waxes Hydrocarbons, Lipid – soluble Insoluble in water vitamins, Micronutrients and Soluble in non-polar solvents (ether, Hormones chloroform) High energy value of fats, EFA, FSV Neutral Lipids Uncharged Simple Lipids Acylglycerols (glycerides), Esters of FA with alcohols Cholesterol, Cholesteryl esters 1. Fats – FA with glycerol 2. Waxes – esters of FA with FATTY ACIDS HMWMA Esters in naturals fats and oils but are Complex Lipids found in the unesterified form as free Esters of FA that contain alcohol and fatty acids, a transport form in the one or more FA plasma. 1. Phospholipids – contain a Usually contain even number of phosphoric acid, have carbon atoms. nitrogen containing bases (ex. Saturated (no double bonds) choline). In many Unsaturated (has double bonds) phospholipids the alcohol is glycerol (glycerophospholipids), sphingosine (sphingophospholipids), which contain nitrogen group. 2. Glycolipids (glycosphingolipids) – contain a FA, sphingosine, and Carbon atoms are numbered from carboxyl carbohydrate. carbon (carbon no.1), adjacent to the CC are 3. Other Complex Lipids – also known as α, β, γ carbons. Sulfolipids and amino lipids and lipoproteins Terminal methyl carbon is known as ὦ or n Derived Lipids carbon. Formed from hydrolysis of both simple and complex lipids Saturated FA Contain No Double Bonds Prostaglandin Local hormones Synthesized in vivo by cyclization of the center of the carbon chain of 2- carbon PUFA to form a cyclopentane ring Thromboxane Cyclopentane ring with oxygen atom Leukotriene and Lipoxin Third group of eicosanoid derivatives formed via the lipoxygenase pathway. Characterized by the presence of 3 or Saturated FA Contain One or More Double 4 conjugated double bonds Bonds LTs causes bronchoconstriction, potent inflammatory agents and asthma 1. Monounsaturated – one double bond 2. Polyunsaturated – two or more double Most Naturally Occurring Unsaturated Fatty bonds Acids Have cis Double Bond 3. Eicosanoids – derived from eicosa (20 The carbon chains of saturated fatty acids carbons) polyenoic FA. form a zigzag pattern when extended at low Ex. temperatures. At higher temperatures, Prostanoids (Prostaglandins, Prostacyclins, some bonds rotate, causing chain Thromboxanes), Leukotrienes and Lipoxins shortening. Cis – Omega 3 FA are Anti – Inflammatory and Same sides of hydrogen atom Have Health Benefits Bent (120 degree) at double bond Alpha Linolenic – found in plants oils Occurs naturally Eicosapentaenoic (EPA) – found in Trans – fish oils Opposite sides of hydrogen atom Docosahexaenoic (DHA) – found in Found in hydrogenated oils fish and algal oils From bacterial synthesis Due to their promotion of the synthesis of less inflammatory PGs and LTs as compared to Omega 6 FA. Their potential use as a therapy in severe chronic disease where inflammation is contributory cause is under intensive investigation. Current evidence suggests that diets rich in Omega 3 FA are beneficial for: Cardiovascular disease, Cancer, Rheumatoid Arthritis and Alzheimer disease. Trans Fatty Acids By product of the saturation of FA Triacylglycerols: Main Storage Forms of FA during hydrogenation or hardening TAGs are esters of the trihydric alcohol of natural oils in the manufacture of glycerol and fatty acids. margarine. Mono/Diacylglycerols, one or two FA are Consumption is known to be esterified with glycerol, are also found in the detrimental to health and is tissues. associated with increased diseases including cardiovascular disease and Essential Fatty Acids diabetes mellitus. Must be in diet (supplied through diet) Physiologic Properties of Fatty Acids Tissues cannot synthesize The melting points of even-numbered Linoleic Acid (18:2): Omega 6 FA carbon FA increase with chain length and Linolenic Acid (18:3): Omega 3 FA decrease according to unsaturation. *Arachidonic Acid – becomes essential if Saturated = solid at body temp C18:2 is deficient in the diet Unsaturated = liquid to below 0 degree Deficiency in EFA Abundant in plasma membrance Growth retardation “lipid rafts” Problems with reproduction Large quantities in myelin sheath Skin lesions that surround nerve fibers Kidney and Liver Disorders Cell signaling and Apoptosis Arachidonic Acid Substrate for Prostaglandin synthesis Synthesized in Liver Thromboxane Prostacyclin Leukotriene Neurotransmitter Phosphatidylcholines (Lecithins) Cytochrome P450 Most abundant phospholipids of the cell membrane Phospholipids: Main Lipid Constituents of Choline is important in nervous Membranes transmission Many phospholipids are derivatives of Dipalmitoyl Lecithin – surface active phosphatidic acid, which the phosphate is agent and surfactant preventing esterified with one OH group of glycerol and adherence, due to inner surface of the other OH grous are esterified to two long the lungs. May cause Respiratory chain fatty acids (glycerophospholipids). Distress Syndrome. Sphingolipids, such as sphingomyelin, which Phosphatidylethanolamine (Cephalin) the phosphate is esterified to sphingosine, a Found in cell membranes complex amino alcohol, are also important membrane component. Phosphatidylserine Plays a role in Apoptosis Both glycerophospholipids and (programmed cell death) sphingolipids have two long chain hydrocarbon tails which are important for Phosphatidylinositol their function in forming the lipid bilayer in cell membranes. Stereoisomer of Myoinositol Phosphorylated Phosphatidylinositol Sphingomyelin (phosphoinositide), a minor Outer leaflet of the cell membrane components of cell membranes, lipid bilayer plays in cell signaling and membrane trafficking.  PiP2 (phosphatidylinositol 4,5 – Plasmalogens biphosphate) cleaved to Constitute as much as 10% - 30% of diacylglycerol and inositol the phospholipids of brain and heart triphosphate, act as internal signals Structurally, plasmogen resembles or second messengers. phosphatidylethanolamine May have protective effect against oxygen species Glycolipids Lipids with attached carbohydrate Widely distributed in every tissue esp nervous tissue such as brain Forms glycocalyx, cell surface carbohydrates in plasma membrane Galactosylceramide Major glycosphingolipid of brain and other nervous tissue Contains a number of characteristcis C24 FA (eg. Cerebronic acid) Can be converted to sulfogalactosylceramide (sulfatide) Cardiolipin Phosphatidic acid is a precursor of phosphatidylglycerol. Found only in mitochondria Essential for mitochondrial function. Decreased level may cause mitochondrial dysfunction in aging, including heart failure hypothyroidism and Barth syndrome. Gangliosides Often found as cholesteryl ester, Derived from glucosylceramide that where the OH group on position 3 is contain in addition one or more esterified with a LCFA. molecules of sialic acid. Occurs in animals but not in plants or Present in nervous tissues in high bacteria concentration. Cell – cell recognition and communication Receptors for hormone and bacterial toxin such as cholera toxin. Steroids Bile Acids Cyclic Nucleus resembling Lipid emulsifying agent in the phenanthrene to which a aqueous environment of the cyclopentane ring is attached. digestive tract Elimination of excess cholesterol Synthesize in the liver and stored in the gall bladder Sex Hormones Androgens – primarily testosterone, stimulates male reproductive system Sterols and secondary sex characteristics Special form of steroids with Estrogens – estradiol; most hydroxyl group at C3 important, responsible for female Aka steroid alcohols reproductive system Most common: Cholesterol and Progestin – progesterone; involved in Vitamin D preparing and maintaining tissues of Cholesterol the uterus required to support the Precursor of large number of equally growth and development of embryo important steroids that includes bile acids, adrenocortical hormones, sex hormones, vitamins D and cardiac glycosides. Major constituent of the plasma membrane Glucocorticoids For inflammatory disorder Cortisol – helps body deal with stress and control metabolism Corticosterone – suppress inflammatory reactions Polyprenoids Synthesized like cholesterol from 5 Steroids Stereoisomers carbon isoprene units Each six carbon rings of steroid Ubiquinone, respiratory chain in nucleus is capable of existing in 3 mitochondria dimensional conformation, “chair or Dolichol, glycoprotein synthesis by boat” transferring carbohydrate residues Chair – more stable conformation Plant – derived polyprenoids: rubber, camphor, the fat – soluble vitamins A,D,E,K and beta – carotene (provitamin A) Lipid Perodixation Chain reaction in which free radicals formed in the initiation stage in turn generate more and has potentially devastation effects. Ergosterol Occurs in plants and yeast Peroxidation of lipids exposed to oxygen is Important dietary source of Vitamin responsible not only for deterioration of D foods but also for damage to tissues in vivo. When irradiated with UV light in skin, May be cause of cancer, inflammatory ring B opens to form Vitamin D2, diseases, atherosclerosis and aging. similar to Vitamin D3 from 7 dehydrocholesterol The deleterious effects are considered to be caused by free radicals. Free Radicals Molecules that have unpaired valence electrons, making them highly reactive If containing oxygen, termed as reactive oxygen species (ROS) Produced during peroxide formation from FA containing methylene – interrupted double bonds in PUFA. Antioxidants Used to control and reduce lipid peroxidation both by humans in their activities and in nature. Preventive Antioxidants – reduce the rate of chain initiation (eg. Glutathione) Chain breaking Antioxidants – interfere with chain propagation (eg. Vitamin E) Propyl gallate, Butylated hydroxyanisole (BHA) and Butylated hydroxytoluene (BHT), used as food additives Urate and Vitamin C, water soluble Beta – Carotene, antioxidant at low PO2.