Lipids PDF

Lipids Clarisse Kim C. Felisco, RMT, MSMT Department of Medical Technology School of Nursing and Allied Medical Sciences LIPIDS q Known as fats – provide a major way of storing chemical energy and carbon atoms in the body q Surround and insulate vital body organs, providing protectio...

Lipids Clarisse Kim C. Felisco, RMT, MSMT Department of Medical Technology School of Nursing and Allied Medical Sciences LIPIDS q Known as fats – provide a major way of storing chemical energy and carbon atoms in the body q Surround and insulate vital body organs, providing protection from mechanical shock and prevents excessive loss of energy q Organic compounds found in living organisms that is insoluble or sparingly insoluble in water but soluble in organic solvents 01 CLASSIFICATIONS Classification According To Function a. Triglycerides – storage form of energy b. Phospholipids & Cholesterol – structural components of biomembranes c. Steroid hormones – metabolic regulators d. Amphipathic lipids – surfactants, detergents, emulsifying agents e. Electric insulators in neurons f. Subcutaneous fats – provides insulation against changes in external temperature g. Give shape and contour to the body h. Cushioning effect i. Help in absorption of fat soluble vitamins (A, D, E, and K) Classification According To Structure Simple lipids – esters of fatty acids with glycerol or higher alcohols Compound lipids – fatty acids esterified with alcohol and contain other groups ○ phospholipids – contains phosphoric acid ○ Non-phosphorylated lipids Derived lipids – derived from lipids or precursors of lipids ○ Fatty acids, steroids 02 FATTY ACIDS Fatty Acids simple linear chain of C-H bonds that has a carboxyl group (1C) and methyl group at the end Can be classified according to the number of Carbon atoms ○ Long-chain fatty acids (C12 – C26) ○ Medium-chain fatty acids (C8 – C12) ○ Short-chain fatty acids (C4 – C6) R – CO – OH – general formula PHYSICAL PROPERTIES: FATTY ACIDS Water solubility ○ Solubility decreases as carbon chain length increases Melting points ○ Strongly influenced by carbon chain length and number of double bonds present ○ As carbon chain increases, melting point increases ○ The greater number of double bonds, less melting points  TYPES OF FATTY ACIDS Saturated Fatty Acids Unsaturated Fatty Acids ○ Monounsaturated fatty acid (MUFA) ○ Polyunsaturated fatty acid (PUFA)  SATURATED FATTY ACIDS Fatty acids without double bonds in the entire hydrocarbon chain Ends with “- anoic acid” UNSATURATED FATTY ACIDS There is a presence of double bond in the entire hydrocarbon chain Ends with “-enoic acid” Monounsaturated Polyunsaturated  MONOUNSATURATED FATTY ACIDS Fatty acid with a hydrocarbon chain with one carbon- carbon double bond Cis trans POLYUNSATURATED FATTY ACIDS Fatty acid with a hydrocarbon chain with 2 or more carbon-carbon double bonds 03 SIMPLE LIPIDS ENERGY-STORAGE LIPIDS: TRIACYLGLYCEROLS simplest and most abundant type of lipid Concentrated primarily in adipocytes More efficient than glycogen ○ Large quantities can be packed into small volumes TRIACYLGLYCEROL Lipid formed by esterification of 3 fatty acids to a glycerol molecule Triglyceride – old name Simple triacylglycerol – formed from the esterification of glycerol with 3 identical fatty acid molecules Mixed triacylglycerol – formed from the esterification of glycerol with more than 1 kind of fatty acid molecule TRIACYLGLYCEROL An ester linkage of three fatty acids and glycerol Each fatty acids tends to be different thus producing many possible structures for triglyceride Triglyceride with saturated fatty acids are more tightly packed thus more solid Triglyceride with cis unsaturated fatty acids are fluid in nature 04 COMPOUND LIPIDS  Compound lipids Simple fatty acid with additional polar group Generally, amphipathic in nature Phosphoglycerides Phospholipids Sphingomyelin Cerebroside Sulphatides Compound Globosides Glycolipids Lipids Gangliosides Chylomicrons VLDL Lipoproteins LDL HDL  Phospholipids Major component of cell membrane (lipid bilayer) It has an alcoholic backbone with 2 esterified fatty acids (non-polar tail) and a phosphate group (polar head) Amphipathic ○ Polar head – extend to the exterior (aqueous This Photo by Unknown Author is licensed under CC BY environment) ○ Non-polar head – moves toward the interior of the membrane  Phospholipids Phosphoglycerides o Found in large quantities in the brain and nerve tissues o Nerve fiber insulator o Marker for apoptosis Sphingomyelin o Most abundant lipid of the cell membrane (55-70%) o Act as lung surfactant: dipalmitoyl lecithin o Source of inositol triphosphate and diacylglycerol (generated from phosphatidyl inositol biphosphate) o Essential for lipoprotein structure  Phosphoglycerides Phospholipid with glycerol backbone and an alcohol group attached on the phosphate group Alcohol groups: Ethanolamine [CH2OHCH2NH2] Cephalin Choline [-CH2CH2-N+(CH3)3] Lecithin Serine [CH2CHCOO—NH3] Phosphatidyl serine - Glycerol CH2OHCHOHCH2OH Phophatidyl glycerol Phosphatidyl PHOSPHOLIPID inositol Inositol  Sphingomyelin Parts of Sphingomyelin structure ○ Sphingosine backbone 18C chain with amino group on the second carbon (2C) and one hydroxyl group each on the first (1C) and third carbon (3C) ○ Ceramide A sphingosine backbone with a fatty acid chain on the amino group ○ Alcohol group Sphingosine with a phosphate polar head, the alcohol group attached on the phosphate group  Glycolipids Same structure with sphingomyelin except that it contains carbohydrate (polar group) on the first carbon atom of the ceramide molecule and has no phosphate group Essential component of biological membrane with highest concentration found in nerve tissue Depending on the nature of carbohydrate, 4 types can be recognized: ○ Cerebroside ○ Sulfatides ○ Globosides ○ Gangliosides  Lipoprotein Complex of lipid and protein Act as lipid transporter 4 major types: Chylomicrons VLDL LDL HDL Largest but the least Most atherogenic transporter Most abundant Smallest but the most dense of triglyceride lipoprotein (50%) dense 90% Triglyceride 65% Triglyceride 50% Cholesterol ester 30% Phospholipid 1-2% Protein 16-22% Cholesterol ester 28-32% other lipids 15% Cholesterol ester 8-9% Other lipids 6-10% Protein 18-22% Protein 45-50% Protein Transport exogenous Transport endogenous Transport dietary Transport excess triglyceride to hepatic triglyceride to peripheral cholesterol to peripheral cholesterol to the liver cells tissues tissue 05 DERIVED LIPIDS  Steroids Complex lipid molecules consisting of 17 carbon atoms bonded in four fused rings: 3 six-membered ring and a cyclopentane – collectively named as steroid nucleus Steroids with alcohol derivative linked in the steroid nucleus is are termed as sterol Cholesterol – the most common sterol in mammals  Cholesterol Classified as lipid because they are hydrophobic and insoluble in water, but do not resemble lipids in terms of structure May exist as free or esterified form ○ Free cholesterol is amphipathic as it has single polar group (hydroxyl group) ○ Esterified cholesterol (Cholesterol esters) is hydrophobic as fatty acid is esterified in the hydroxyl group neutralizing the polarity of the molecule Precursor for 3 useful compounds: bile acid, steroid hormones, and vitamin D. Essential component of all biological membrane Component of nerve fibers  Cholesterol The nucleus is made up of three six-membered rings (A, B, C) and a cyclopentane (D) collectively known as cyclopentanoperhydrophenanthrene Has single polar group and the rest are non-polar It has trans conformation in the hydrogen molecules of carbons 9, 8, and 14 resulting to more rigid structure due to tight packing of molecules lessening molecular spaces 06 Fats and oils  Fats Vs Oils: What Are The Differences? FATS OILS Triacylglycerol mixture that is solid Triacylglycerol mixture that is or semi-solid at room temperature liquid at room temperature (25C) (25C) Obtained from plant sources Obtained from animal sources 07 DIGESTION AND ABSORPTION OF FATS  MOUTH Water-based salivary enzymes will have little to no effect on triacylglycerol. STOMACH Small amount of lipid digestion occurs in the stomach due to gastric lipase.  LIVER Bile produced in the liver, stored in the gallbladder, is released to the small intestine to aid in digestion and absorption of lipids. PANCREAS Pancreatic lipase produced in the pancreas is released into the small intestine.  SMALL INTESTINE Products from fat digestion and bile acids form micelle and moves to the microvilli to allow lipids to diffuse into mucosal cells.  DIGESTION IN THE INTESTINES Emulsification – prerequisite for digestion lipids Lipids are dispersed into smaller droplets, surface tension is reduced, surface area is increased Favored by: ○ Bile salts ○ Peristalsis ○ phospholipids BILE SALTS Sodium glycocholate & Sodium taurocholate – lowers surface tension Emulsify fat droplets and increases surface activity for enhancement of enzyme activity MICELLES Circular in structure Characterized by non- polar tails situated inside bile acids found outside Hydrophilic exterior and hydrophobic interior Essential for absorption of fat-soluble vitamins (A, D, E, and K) CHYLOMICRONS Absorbed triglycerides are transported in the blood as chylomicrons Taken up by the adipose tissue and liver During starvation states, triglycerides in the adipose tissues are hydrolyzed and produces free fatty acids ○ Transported through the help of albumin This Photo by Unknown Author is licensed under CC BY-SA-NC 10 KETONE BODIES KETONE BODY One of the 3 substances produced from acetyl CoA when an excess of acetyl CoA from fatty acid degradation accumulates because of triglyceride-carbohydrate metabolic imbalances ○ Dietary intake high in fat and low in carbohydrates ○ Diabetic conditions ○ Prolonged fasting conditions 11 CHOLESTEROL CHOLESTEROL Unsaturated steroid alcohol containing 4 rings with a single C-H side chain tail attached to a fatty acid Amphipathic Found on the surface of lipid layers and synthesized in the liver Functions: ○ Precursor of 5 major classes of steroids: progestins, glucocorticoids, mineralocorticoids, androgens and estrogens ○ Important constituent in the assembly of cell membranes and bile acids FORMS OF CHOLESTEROL Free Cholesterol (FC) ○ Found in plasma, serum, and RBC ○ Produced from lysosomal hydrolysis ○ Found on the surface of lipopropteins Cholesterol Ester (CE) ○ Found in the plasma and serum ○ Cholesterol bound to fatty acid 12 EMULSIFICATION LIPIDS: BILE ACIDS EMULSIFIER A substance that can disperse and stabilize water-insoluble substances as colloidal particles in an aqueous solution Bile acid – cholesterol derivative that functions as a lipid- emulsifying agent in the aqueous environment of the digestive tract Bile – fluid containing emulsifying agents that is secreted by the liver, stored in the gallbladder and released into the intestine during digestion 13 STEROID HORMONES Hormones biochemical substance produced by ductless glands that has a messenger function Steroid hormone – hormone that is a cholesterol derivative ○ sex hormone – controls reproduction and secondary sex characteristics ○ adrenocorticoid hormones – regulation of biochemical processes in the body Sex Hormones Estrogens – synthesized in the ovaries and adrenal cortex ○ development of female secondary sex characteristics at puberty and regulation of menstrual cycle Androgens – synthesized in the testes and adrenal cortex Progestins – synthesized in the ovaries and placenta ○ prepares the lining of the uterus Adrenocorticoid Hormones Produced by the adrenal glands Mineralocorticoids – balance of Na and K ions ○ aldosterone Glucocorticoids – controls glucose metabolism ○ cortisol 14 EICOSANOIDS EICOSANOIDS oxygenated C20 fatty acid derivative that functions as a messenger lipid precursor: arachidonic acid Physiological effects ○ inflammatory response ○ production of pain and fever ○ regulation of blood pressure ○ induction of blood clotting ○ control of reproductive functions ○ regulation of sleep/wake cycle 3 Principal Types of Eicosanoids Prostaglandins ○ contains cyclopentane ring and oxygen-containing functional groups ○ involved in many regulatory functions – increasing body temp., inhibiting secretion of gastric juices, enhancing inflammation response Thromboxanes ○ contains cyclic ether ring and oxygen-containing functional groups ○ promotes formation of blood clots, produced by platelets 3 Principal Types of Eicosanoids Leukotrienes ○ contains 3 conjugated double bonds and hydroxy group ○ found in leukocytes 15 BIOLOGICAL WAXES Biological Waxes lipid that is a monoester of a long-chain fatty acid and long chain alcohols protect hair and skin pharmaceutical, cosmetics, polishing industries (e.g. Lanolin) 16 Saponifiable and Nonsaponifiable Lipids Saponification a hydrolysis reaction that is carried in basic solution Saponifiable lipid – lipid that undergoes hydrolysis in basic solution to yield two or more smaller product molecules Nonsaponifiable lipid – does not undergo hydrolysis in basic solution  Thanks! 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