Week 8 - Lipids PDF

LIPID Chemistry  OBJECTIVES Define lipids and its occurrence State the biological significance of fats Define chemical composition of fats Define physical properties of fats Define chemical properties of fats Classify lipids into fatty acids, triglycerides, steroids Defin...

LIPID Chemistry  OBJECTIVES Define lipids and its occurrence State the biological significance of fats Define chemical composition of fats Define physical properties of fats Define chemical properties of fats Classify lipids into fatty acids, triglycerides, steroids Define phospholipids Describe the chemistry and functions of cholesterol Explain lipoproteins Explain messenger lipids What is Lipid A lipid is an organic compound found in living organisms that is insoluble in water but soluble in non-polar organic solvents. Unlike other biomolecules, lipids do not have a common structural feature Composition of lipid SOME EXAMPLE OF LIPIDS  FIVE CATEGORIES OF LIPIDS 2. Membrane lipids - 3. 1.energy- phospholipids, emulsification storage lipids - sphingoglycolip lipids - bile triacylglycerols ids, and acids cholesterol 4. chemical messenger 5. protective- lipids - steroid coating lipids hormones - biological andeicosanoids waxes )  Function of Lipids Energy storage Thermal Membrane (as Metabolic fuels insulation components triacylglycerol) emulsifying Hormones Precursors of agents in the (steroids and prostanoids Vitamins A, C, digestion and vitamin D and D, E, and K absorption of metabolites) leukotrienes lipids Participation in Surfactants in the signal the alveolar transduction membrane pathways Lipoprotein & Phospholipids Acts as fuel Insulating (cell wall & in the body effect mitochondrion constituents) Padding & protection of internal organs Vitamin A,D,E,K fat Building soluble Materials vitamins (hormone s) Supply Nervous essential fatty system: Rich acids in lipids 9 Classification of Lipid  FATTY ACIDS structural components of all the lipids Most biological fatty acids contain an even number of carbon atoms. Although the molecule is water-insoluble, the negatively charged carboxylate is hydrophilic. Properties of Fatty Acids Fatty acids undergo the same reactions as other carboxylic acids, such as esterification and acid-base reactions. The acidities of fatty acids do not vary greatly, as indicated by their pKa values. The solubility of fatty acids in water decreases as chain length increases so that longer-chain fatty acids have little effect on the pH of an aqueous solution. Fatty acids exist at their conjugate bases, such as oleate, near neutral pH. FATTY ACIDS: SATURATED VS UNSATURATED Saturated fatty acids: – Bad cholesterol; (low density lipoprotein) – Solid at room temperature Unsaturated fatty acids – Good cholesterol ( high density lipoprotein) – Liquid at room temperature SATURATED FATTY ACIDS  Unbranched, linear chains of CH2 groups linked by carbon-carbon single bonds with one terminal carboxylic acid group.  The maximum possible number of hydrogen atoms Common Systematic are bonded to eachname carbon#in of the Typical sources molecule. name carbons Lauric acid n-dodecanoic acid 12 Palm kernel oil, nutmeg Myristic acid n-tetradecanoic acid 14 Palm kernel oil, nutmeg Palmitic acid n-hexadecanoic acid 16 Olive oil, animal lipids Stearic acid n-octadecanoic acid 18 Cocoa butter, animal lipids Behenic acid n-docosanoic acid 22 Brain tissue, radish oil Lignoceric acid n-tetracosanoic acid 24 Brain tissue, carnauba wax  MONOUNSATURATED FATTY ACIDS Dietary effect is a decrease in heart disease risk Common Systematic name # of Typical sources name carbons Palmitoleic cis-9-hexadecenoic 16 Marine algae, acid acid pine oil Oleic acid cis-9-octadecenoic 18 Animal tissues, acid olive oil Gadoleic acid cis-9-eicosenoic acid 20 Fish oils (cod, acid sardine) Erucic acid cis-13-docosenoic acid 22 Rapeseed oil acid Nervonic acid cis-15-tetracosenoic 24 Sharks, brain  NAMING MONOUNSATURATED FATTY ACIDS see structural notation: it indicates number of c atoms and the number of c-c double bonds present e.g., 18:2 – 18 carbons, 2 double bonds to specify double-bond positioning within the c chain of an unsaturated fatty acid, add Greek capital letter delta (∆) followed by one or more superscript numbers. e.g., 18.3 (∆9,12,15) POLYUNSATURATED FATTY ACIDS More than one carbon-carbon double bond it is cis in nature They are found in relatively minor amounts. Omega 6 and Omega 3 POLYUNSATURATED FATTY ACIDS Common name Systematic name # of carbons Typical sources Linoleic acid cis-9-, cis-12-octadecadienoic acid 18 corn oil, animal tissues, bacteria Linolenic acid cis-9-, cis-12-, cis-15-octadecatrienoic 18 animal tissues acid 5,8,11-eicosatrienoic acid 20 8,11,14-eicosatrienoic acid 20 brain tissue 7,10,13-docosatrienoic acid 22 phospholipids 8,11,14-docosatrienoic acid 22 Arachidonic 5,8,11,14-eicosatetraenoic acid 20 liver, brain tissue acid 4,7,10,13-docosatetraenoic acid 22 brain tissue 4,7,10,13,16,19-docosahexaenoic 22 brain tissue acid  TRANS FATTY ACIDS Trans polyunsaturated fatty acids are a minor product of animal and plant metabolism They are also produced synthetically by partial hydrogenation of fats and oils in the manufacture of margarine (the so- called trans fats). The most widely used method to increase the melting point to dietary fats, In addition, it favors freshness, gives texture and improves stability  CHARACTERISTICS OF FATTY ACIDS The melting point of fatty acids increases with increasing chain length The even-numbered saturated fatty acids having higher melting points than the odd- numbered. Increase cis double bonds = lower melting point The longer the chain = the less soluble it is  SPACE-FILLING MOLECULES the amount of bends in a fatty acid chain increase as the number of double bonds increase a. less packing occurs b. melting point is lower c. tend to be liquids at room temperature ENERGY-STORAGE MATERIALS A. 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 amounts B. storage material is the triacylglycerols: triacylglycerols are concentrated primarily in special cells (adipocytes) nearly filled with the material.  TRIGLYCERIDES Triglycerides: storing fatty acids in biological systems Almost all naturally occurring triglyceride molecules, however, contain more than one type of fatty acid.  PROPERTIES OF TRIGLYCERIDES Hydrophobic substances that are soluble only in some organic solvents. They possess no electric charges and are therefore referred to as neutral lipids. Melted triglycerides are generally quite viscous oils. It is important that most stored triglycerides be fluid at body temperature in order to permit their rapid mobilization as an energy source. TWO TYPES OF TRIACYLGLYCEROLS Simple triacylglycerols: three identical fatty acids are esterified Mixed triacylglycerols: a triester formed from the esterification of glycerol with more than one kind of fatty acid  DIFFERENCE OF FATS AND OILS 1. FATS 2. OILS: solids or Source -animal predominantly semisolids at predominantly liquids at room Source – plant source and saturated room unsaturated temperature and fish oil tasteless temperature  “GOOD FATS” VERSUS “BAD FATS” studies indicate that type of dietary fat and amount of dietary fat are important for balanced diet: current recommended amounts are: total fat intake in calories: 15% - monounsaturated fat 10% - polyunsaturated CHEMICAL REACTIONS OF TRIACYLGLYCEROLS chemical properties due to two functional groups: esters and alkenes 2. 1. saponificati hydrolysis on 3. hydrogenat 4. oxidation ion  Hydrolysis of triacylglycerol hydrolysis of triacylglycerols is the reverse of esterification reaction breaking of 1-2 ester bonds to give rise to mono- or diacylglycerol and fatty acid(s) within the human body, it is carried out by enzymes produced by the pancreas aka lipase  SAPONIFICATION hydrolysis in basic solution: produce salt of fatty acid and glycerol today most soap is prepared by hydrolyzing fats and oils (animal fat and coconut oil) under high pressure and high temperature and sodium carbonate is used as the base CLASSIFICATION OF LIPIDS IN CATEGORIES  OXIDATION double bonds in triacylglycerols are subject to oxidation with oxygen in air (an oxidizing agent )-leads to c=c breakage remember that oxidation of alkenes may result into two short chain molecules – an aldehydes or a carboxylic acid Rancidity Rancidity occurs when fats and oils are exposed to air, moisture, light, bacteria etc. Hydrolytic rancidity occurs due to partial hydrolysis of triacylglycerol by bacterial enzymes. HYDROGENATION OF A TRIACYLGLYCEROL double bonds in unsaturated fatty acids react with hydrogen gas to produce carbon–carbon single bonds. Unsaturated fatty acids may be converted to saturated fatty acids by the relatively simple hydrogenation reaction. WAXES Esters from long chain alcohol (fatty alcohol) and long chain carboxylic acid (fatty acid) Hydrophobic: Waxes are water-repellent and do not dissolve in water. Solid at Room Temperature: Most waxes are solid at typical room temperatures). Low Melting Point: Waxes generally have relatively low melting points,  BIOLOGICAL MEMBRANE LIPIDS Three principal classes of lipids that form the bilayer matrix of biological membranes: Glycerophospholipids, sphingolipids, and sterols (principally cholesterol). Glycerophospholipids Sphingolipids Sterols BIOLOGICAL MEMBRANE LIPIDS  MEMBRANE LIPIDS: PHOSPHOLIPIDS all cells are surrounded by a membrane that confines their contents. up to 80% of the mass of a cell membrane can be lipid materials and these lipid materials are dominated by phospholipids. Functions of phospholipids Structural components of membranes. Help in electron transport. They absorb fat from intestine. They absorb fat from liver and prevent accumulation of fat in liver. They are essential for synthesis of lipopoteins. They participate in blood  Glycerophospholipids The most abundant in biological membranes. They are composed of a glycerol backbone, two fatty acid tails, and a phosphate head group.  Types of Glycerophospholipids Phosphatidylcholine: One of the most common phospholipids in cell membranes. Phosphatidylethanolamine: Another common phospholipid with a smaller head group. Phosphatidylserine: Carries a negative charge and is often found in the inner leaflet of the membrane. Phosphatidylinositol: Plays a role in cell signaling and membrane trafficking. Phosphatidylcholine Also known as lechithins Waxy solids that forms colloidal suspensions in water Dietary sources: eggs yolk, soybeans Within body prevalent/ present in cell membrane Sphingolipids  A second major class of lipids associated with the cell membrane  Are based on an 18-carbon amine alcohol, sphingosine The single deviant member is sphingomyelin, a molecule with a phosphorylcholine group (the same polar head group as in phosphatidylcholine) instead of the sugar moiety. All sphingolipids have, in addition to the sugar, a fatty acid attached to the amino group of sphingosine. Among the sphingolipids, only sphingomyelin, a phospholipid, is a major component of biological membranes.  SPHINGOGLYCOLIPIDS All containing a sugar attached to carbon 1 of sphingosine  Neutral glycosphingolipids: contain only neutral sugars and are found exclusively on the external surface of the cell membrane, where their sugar moieties often act as antigens and as receptors for hormones and other signaling molecules.  they occur primarily in brain (7% of dry mass) Gangliosides contain one or more sialic acid residues linked to the sugar. More complex form of sphingoglycolipid Contains a branched chain of up to 7 monosaccharide residues Gray matter of the brain Cerebrosides The simplest form of shyngoglycolipids Contains a single monosaccharide unit either glucose or galactose Occur primarily in the brain Also present in myelin sheath  What is Cholesterol? Are light yellow crystalline solid Are soluble in chloroform and other fat solvents Polyunsaturated acids – lower the plasma cholesterol level The most abundant lipid in the human body 50  What is Cholesterol?  Are synthesized in the liver, adrenal cortex, intestines, testes and skin.  Play an important role as a component of biomembranes and has a modulating effect on the fluid state of the 51  CHOLESTEROL Cholesterol is a member of a class of lipids called isoprenoids These molecules are formed by chemical condensation of a simple five-carbon molecule, isoprene. Isoprenoids include: steroid hormones, sterols (cholesterol, ergosterol, and sitosterol), bile acids, the lipid-soluble vitamins (A, D, E, and K), phytol (chlorophyll), etc.  CHOLESTEROL no fatty acid residue and glycerol/sphingosine present lipids: fused rings cholesterol: c27 steroid molecule. a steroid is a lipid whose structure is based on a fused ring system of three 6 carbon rings and one 5 carbon ring. (steroid nucleus) the most abundant steroid in the human body.  What is  Cholesterol? Can be estimated by color reactions (e.g. Liebermann- Burchard reaction) – blue or green color 54 Function of Cholesterol? An important tissue  It neutralizes the component (modulating hemolytic action of effect, integrity & various agents such permeability) as venom, bacterial Play an important role in toxins insulating nerves and  It gives rise to brain structure “provitamin D” For transport of fatty  It is a precursor of acids in the body cholic acid in the It is a part of lipoproteins body as also bile salts.  It gives rise to sex 55  Functions of Cholesterol Atherosclerosis Diabetes Plaque around Mellitus The artery Myxoedema Hardening & (Hypothyroidis Narrowing m) CHOLESTER OL Hyperthyroidi Xanthomato sm sis (fat storage Obstructive jaundice disorder) Nephrotic syndrome (kidney disorder) 56 Cholesterol important in human cell membranes, nerve tissue and brain tissue important in chemical synthesis: hormones, vitamins essential for life a) cell membranes – 25% by mass b) nerve and brain tissue – 10% by dry mass c) every 100 ml of blood plasma – 50 mg and about 170 mg of cholesterol esterified with various fatty acids d) most cholesterol is biosynthesized by the liver and the intestine e) about 800-1000 mg each day CHOLESTEROL IN FOOD liver synthesizes cholesterol: ~ 1g everyday; so it is not necessary to consume in the form of diet cholesterol synthesis decrease if it is ingested but reduction is not sufficient: leads to cardiovascular disease animal food: lot of cholesterol plant food: no cholesterol  What are Lipoproteins? Are conjugated proteins involved in transport and delivery of lipids to tissues. E.g. Lipids (Cholesterol & triglycerides) + water soluble carrier proteins It transport neutral lipids in the blood. It has lower density than the ordinary protein molecule. 59  Lipoproteins according to Density Type Densit Protein Triglyceri Cholesterol Phospholipi y des ds g/ml (TAG) Free Ester Chylomicro < 0.95 1 85-95 1-2 1-2 3-6 ns Very low 0.95- 10 50-60 4-8 10 15-20 density 1.006 lipoprotein VLDL Low 1.006- 22 10 10 38 20 density 1.063 lipoprotein s LDL High 1.063- 45-60 3 5 15-20 25-30 density 1.21 62  Distribution of Lipoproteins: Body tissues Nucleus, Cell Plasma membranes Cholesterol, Mitochondria Phospholipids, Microsome neutral fat, traces of fat soluble vitamins Steroid hormone LIPOPROTEI Thromboplastin NS Rhodopsin (prothrombin- (combination of thrombin) protein, opsin and retinal aldehyde of Vit. A Egg yolk (HDL & LDL) Fat droplets in milk 63  STEROL Major components of biological membranes in eukaryotes but are rare in prokaryotes Cholesterol is the principal sterol of animals, whereas the major sterol in fungi is ergosterol and that in plants is sitosterol.  STRUCTURE OF BILE ACIDS Steroid nucleus: Bile acids are derived from cholesterol, a steroid lipid. Hydroxyl groups: Bile acids have multiple hydroxyl groups that increase their hydrophilicity and solubility in water. Conjugation: Bile acids are often conjugated with glycine or taurine, which further increases their solubility and helps to neutralize their acidic properties.  FUNCTION OF BILE ACIDS Emulsification: Bile acids reduce the surface tension of fat droplets, breaking them down into smaller micelles. This process increases the surface area available for lipase enzymes to digest fats. Micelle formation: Bile acids form mixed micelles with fatty acids, glycerol, and other lipids. These micelles transport lipids to the intestinal mucosa for absorption. Absorption of lipids: Bile acids facilitate the absorption of dietary fats, fat-soluble vitamins (A, D, E, and K), and cholesterol from the small intestine.Stimulation of bile flow: Bile acids can stimulate the secretion of more bile by the liver, enhancing fat digestion and absorption.  HORMONES A hormone is a biochemical substance produced by a ductless gland that has a messenger function. hormones serve as a means of communication between various tissues. Some hormones are lipids. the lipids that play the role of “chemical messengers” include: 1. steroid hormones – derivatives of cholesterol 2. eicosanoids- derivatives of arachidonic acid  STEROID HORMONES a group of lipids that have fused-ring structure of 3 six-membered rings, and1 five-membered ring.  EXAMPLE OF STEROID HORMONES Progestins (active during pregnancy). Progesterone Glucocorticoids (promoting the synthesis of glucose and suppressing inflammatory reactions). Cortisol Mineralocorticoids (regulating ion balances). Aldosterone (Na+, K+, blood pressure) Estrogens (promoting female sex characteristics). Estradiol Androgens (promoting male sex characteristics). Testosterone STEROID HORMONES https://www.youtube.com/watch?v=431tLBZ7d1o STEROID HORMONES  MESSENGER LIPIDS: EICOSANOIDS arachidonic acid (20:4) derivatives: a. have profound physiological effects at extremely low concentrations. eicosanoids are hormone- like molecules exert their effects in the tissues where they are synthesized. eicosanoids usually have a very short “life.”  PROSTAGLANDINS c20-fatty-acid derivative containing cyclopentane ring and oxygen-containing functional groups involved in raising body temperature, inhibiting the secretion of gastric juices, increasing the secretion of a protective mucus layer into the stomach, relaxing and contracting smooth muscle, directing water and electrolyte balance, intensifying pain, and enhancing inflammation responses.  THROMBOXANES c20-fatty-acid derivative containing a cyclic ether ring and oxygen- containing functional groups promote platelet aggregation.  LEUKOTRIENES c20-fatty-acid derivative containing three conjugated double bonds and hydroxyl groups promote inflammatory and hypersensitivity (allergy) responses  Clinical Significance: Nonsteroidal anti- inflammatory drugs (NSAIDs): Inhibit COX enzymes, reducing the production of eicosanoids and relieving pain, inflammation, and fever. Clinical Significance: COX-2 inhibitors: Selective inhibitors of COX-2 have been developed to reduce inflammation without the side effects associated with COX-1 inhibition.  Activity of the day Choices (Individual work) Make an Niemann-Pick infographics about different lipid or steroid metabolism disease, disorders: gangliosidoses, For each disorder, include: A brief description of the disorder. Tay-Sachs Key facts or statistics (e.g., prevalence, genetic inheritance). disease, Common symptoms or manifestations. Diagnostic methods. Sandhoff disease, Treatment options or management strategies. Krabbe disease, Citations APA No repetitions to your classmates metachromatic leukodystrophy References https://www.youtube.com/watch?v=dKT_9AjO9BE https://www.youtube.com/watch?v=ocdoIdict3M