Introduction. Functions Energy storage Structure of cell membranes Thermal blanket Precursors of hormones (steroids and prostaglandins)

Transcription

1 LIPIDS

2 Introduction Definition: water insoluble compounds Most lipids are fatty acids or esters of fatty acids They are soluble in non-polar solvents such as petroleum ether, benzene, chloroform Functions Energy storage Structure of cell membranes Thermal blanket Precursors of hormones (steroids and prostaglandins) Types: Simple lipids (triglycerides, waxes) omposite lipids (phospholipids, glycolipids) Precursors and lipids derivatives (fatty acids, steroids)

3 Properties of fats and oils fats are solids or semi solids oils are liquids melting points and boiling points are not usually sharp (most fats/oils are mixtures) when shaken with water, oils tend to emulsify pure fats and oils are colorless and odorless (color and odor is always a result of contaminants) i.e. butter (bacteria give flavor, carotene gives color)

4 Fatty acids Fatty acids can be classified either as: saturated (- bonds) or unsaturated (also =) according to chain length: short chain FA: 2-4 carbon atoms medium chain FA: 6 10 carbon atoms long chain FA: carbon atoms essential fatty acids vs those that can be biosynthesized in the body: linoleic and linolenic are two examples of essential fatty acid oleic, stearic nonessential liquid (1 to 6), solid (from 7)

5 Fatty acids arboxylic acid are derivatives of long chain hydrocarbons Nomenclature Stearate stearic acid 18:0 n-octadecanoic acid General structure of saturated fatty acids: n 2n+1 n - carbon atoms in a molecule

6 Fatty acids ommon medium-chain saturated fatty acids: 3 7 butyric acid (butanoic acid) short chain FA 5 11 caproic acid (hexanoic acid) 7 15 caprylic acid (octanoic acid) 9 19 capric acid (decanoic acid) caproic acid

7 Fatty acids common long-chain saturated FA s: : lauric acid (n-dodecanoic acid; 12:0 ) : myristic acid (n-tetradecanoic acid; 14:0 ) : palmitic acid (n-hexadecanoic acid; 16:0 ) ; stearic acid (n-octadecanoic acid; 18:0 ) ; arachidic (eicosanoic acid; 20:0 ) ; lignoceric acid ; cerotic acid

8 iso isobutyric acid Less common fatty acids 3 3 odd carbon fatty acid propionic acid hydroxy fatty acids ricinoleic acid, dihydroxystearic acid, cerebronic acid (found in higher plants) cyclic fatty acids hydnocarpic, chaulmoogric acid (nonedible fat and oil isolated from chaulmoogra oil, used in LEPRSY treatment) R ( 2 ) 12-2 R= 3 3 R ( 2 ) 10-2 chaulmoogric acid hydnocarpic acid

9 Unsaturated fatty acids Monoenoic acid (monounsaturated) n 2n-1 There is free rotation about - bonds in the fatty acid hydrocarbon, except where there is a double bond. Double bond is always cis in natural fatty acids ( 2 ) ( 2 ) leic acid 18:1 n-9(cis) or 18:1 (9Z) Elaidic acid 18:1 (9trans)

10 Unsaturated fatty acids Dienoic acid: linoleic acid 18:2 (9cis, 12cis) (9Z, 12Z) 3 ( 2 ) 4 = 2 = ( 2 ) 7 cis linoleic acid Trienoic acid: linolenic acid 18:3 (9cis, 12cis, 15cis) (9Z, 12Z, 15Z)

11 Unsaturated fatty acids Various conventions are in use for indicating the number and position of the double bond(s) In chemistry: 18 3 ( 2 ) ( 2 ) :1,9 or 9 18:1 In biochemistry: ( 2 ) 7 n , 18:1 or n-9, 18:1

12 omparison of melting points 18:0 18: 1 18:3 Melt.p. 70 o 16 o -11 o Saturated FA (highest melting point) Unsaturated trans (intermediate m.p.) Unsaturated cis (lowest m.p.)

13 Unsaturated fatty acids Polyenoic acid (polyunsaturated, tetranoic acid) 3 Arachidonic acid 20:4 (5Z,8Z,11Z,14Z)

14 The Essential Fatty Acids (EFA) are a group of fatty acids that are essential to human health (mega 6) Fatty acids that contain at least two double bonds, one of them at 6 (carbon atom numbering starts from 3 group). LINLEI AID 18:2 (9,12) is main representative acid of this group 3 1 ( 2 ) (mega 3) Fatty acids that contain at least two double bonds, one of them at 3 (starting from 3 group) LINLENI AID 18:3 (9,12,15) is the basic acid of this group ( 2 ) ( 2 ) 7 18

15 Function of EFAs Formation of healthy cell membranes Proper development and functioning of the brain and nervous system Production of hormone-like substances called Eicosanoids Thromboxanes Leukotrienes Prostaglandins They are responsible for regulating blood pressure, blood viscosity, immune and inflammatory responses.

16 mega-3 sources: Flaxeed oil/canola oil Fish liver oils/fish eggs uman Milk Seafood/Fatty fish - albacore tuna - mackerel - salmon -sardines mega-6 sources: orn oil Peanut oil ottonseed oil Soybean oil Many plant oils They are not present in any olive oil! Proper n-6 to n-3 ratio in a diet is 4:1

17 Soaps hard -sodium soaps e.g. soap bar Na + water soluble soft -potassium soaps, e.g shampoo, shaving soaps, liquid soaps K + water insoluble -barium, magnesium, calcium soaps ( ) 2 Ba Soaps don t work effectively in hard water! polar hydrophilic carboxylate group - nonpolar hydrophobic hydrocarbon chain e.g. stearate Amphipatic (amphiphilic) nature of a soap

18 Soaps rganization of soaps molecules in water + + Na + + Soaps solution - a micelle (emulsion type o/w) + + fat water

19 Detergents Synthesis of detergents ( 2 )n- 3 2 S 4 ( 2 )n- 3 Na ( 2 )n- 3 _ n=10-20 S 2 S 2 Na + alkylbenzene alkylbenzenesulfonic acid sodium salt of alkylbenzenesulfonic acid Detergents work effectively in hard water their barium or magnesium salts are water soluble

20 Simple lipids Glycerides (fats and oils) Glycerol 2 2 glycerol Esters of glycerol - monoglycerides, diglycerides and triglycerides Waxes simple esters of long chain alcohols and long chain fatty acids

21 GLYERIDES 2 ( 2 ) * 1-palmitomonoglyceride 2 ( 2 ) ( 2 ) 16 * ( 2 ) 7 ( 2 ) ( 2 ) ,3-dipalmitodiglyceride 2 1-oleo-2-stearodiglyceride 2 ( 2 ) ( 2 ) 14 Triglyceride (tripalmitin) 2 ( 2 ) 14 3 Function: storage of energy in compact form and cushioning

22 Triglycerides chemical properties Acidic hydrolysis (reaction reversible) 2 2 R 1 R 2 R 3 R R Basic hydrolysis (SAPNIFIATIN, reaction irreversible) + R 3 2 Triglyceride fatty acids glycerol 2 2 R 1 R 2 R 3 R 1 + 3Na Na + R 2 R 3 Na Na 2 2 Triglyceride salts of fatty acids glycerol (soaps)

23 Triglycerides chemical properties Enzymatic hydrolysis (reaction reversible) a STERESELETIVE reaction 2 2 R 1 R 2 Triglyceride R lipase R 1 R 3 Fatty acids of carbons 1 i R 2 2-monoglyceride After ca. 5 minutes isomerization of a fatty acid group from 2 to 1 position occurs. Afterwards hydrolysis of the last FA group happens.

24 Triglycerides chemical properties ardening (hydrogenation) 3 ( 2 ) 7 ( 2 ) 7 2 ( 2 ) Ni 3 ( 2 ) 16 2 ( 2 ) ( 2 ) 7 2 ( 2 ) 7 ( 2 ) ( 2 ) 16 3 Triolein (liquid plant fat) Tristearin (solid fat: margarine) The fastest hydrogenation occurs at position -1 and -3 and for fatty acids rests containing four-three double bonds) Negative side effects: trans fatty acids obtaining, changing of double bond positions, polimerization of double bonds

25 Triglycerides chemical properties Transesterification to make fats more nutritious and healthy, to introduce omega-3 and omega-6 fatty acids to the structure of edible fats. No unfavourable side effects during synthesis Na substitute of cocoa butter 1-stearo-2-oleo-3-palmitin It is the source of structured fats. 2 SRT/MEDIUM AIN FATTY AID MEGA - 3 or -6 FATTY AID 2 SRT/MEDIUM AIN FATTY AID

26 Phospholipids - main components 2 P 2 Glycerol Phosphoric acid ydroxyl compounds: 2 N 2 serine N 3 ethanolamine 2 2 N choline inosytol

27 glycerophospholipids Phospholipids * P Ester bond R Their names depending on R: 2 N N N Phosphatidylserine (cephaline) Phosphatidylethanolamine (cephaline) Phosphatidylcholine (lecithine)

28 17 35 glycerophospholipids 2 * Phospholipids P phosphoester bond N( 3 ) 3 - phosphatidylcholine ( -lecithine) ester bond N P 2 * phosphatidylethanolamine ( - cephaline) hydrophilic hydrophobic Natural phospholipids are L i.

29 plasmalogens Phospholipids - form 10% of brain and muscles phospholipids Ether bond R 1 R 1 rest of an alcohol (mainly unsaturated) R 2 * P N 3 R rest of fatty acids ethanolamine Ethanolamine plasmalogen They have anticancer properties.

30 sfingofosfolipidy Phospholipids -forms the myeline sheath around the axon of a neuron. It is essential for the proper functioning of the nervous system. 3 ( 2 ) 12 N ( 2 ) 12 N R 2 Sphingosine eramide 3 ( 2 ) 12 N Sphingomieline 2 Amide bond R P Ester bond R rests of fatty acids R 1 choline, serine, ethanolamine R 1 rests of

31 3 ( 2 ) 12 N 2 Glycolipids erebrosides - is a sphingolipid (ceramide) with a monosaccharide such as glucose or galactose as polar head group. sphingosine 2 Sugar, e.g. gluctose ( 2 ) ( 2 ) 21 3 Fatty acid, e.g. erebronic acid gangliosides a polar head group that is a complex oligosaccharide. erebrosides and gangliosides, collectively called glycosphingolipids, are commonly found in the outer leaflet of the plasma membrane bilayer, with their sugar chains extending out from the cell surface.

32 Steroids the group of naturally occuing compounds (plants, animals, microorganisms) All of them possess the 4-ring skeleton of STERAN (1,2-cyclopentanoperhydrofenantrene) A B Steran D A 4 R Steroids differ in: mutual arrangement of condensed rings A/B, B/ and /D, degree of unsaturation, and type and length of side chains R 1, R 2 and R B R 2 R D ommon steroids skeleton R 1, R 2 mainly 3 groups R 3 hydrocarbon chain of different length sterols steroids contaning - group in the 3 position

33 3 x holesterol and cholesterol esters 3 x 10 5 x 6 x x x 13 x 17 x The hydroxyl at -3 is hydrophilic; the rest of the molecule is hydrophobic (amphipatic molecule); also 8 centers of asymmetry Functions: -serves as a component of cell membranes (moderates membrane fluidity) -precursor to steroid hormones -storage and transport as cholesterol palmitate esters or esters with linolenic acid Sitosterol (phytosterol, in plants) (to progesteron production) Ergosterol, in fungi (to vit. D2 production)

34 holesterol sources, biosynthesis and degradation diet: only found in animal fat biosynthesis: primarily synthesized in the liver from acetyl-coa; biosynthesis is inhibited by LDL (low density lipoprotein) uptake degradation: only occurs in the liver

35 Lipid bilayer Extracellular matrix Glycoprotein arbohydrate Plasma membrane Glycolipid Microfilaments of cytoskeleton Phospholipid holesterol Proteins ytoplasm Main components of lipid bilayer are: phospholipids, glycosphingolipids and cholesterol (all lipids from 20 to 75%), proteins (ca. 50%), carbohydrates The bilayer has LIQUID-RYSTAL ARATER In the liquid crystal state, hydrocarbon chains of phospholipids are disordered and in constant motion At lower temperature, a membrane containing a single phospholipid type undergoes transition to a crystalline state in which fatty acid tails are fully extended, packing is highly ordered

36 Lipid bilayer holesterol inserts into bilayer membranes with its hydroxyl group oriented toward the aqueous phase and its hydrophobic ring system is very close to fatty acid chains of phospholipids holesterol regulates bilayer fluidity - interaction with the relatively rigid cholesterol decreases the mobility of hydrocarbon tails of phospholipids In the absence of cholesterol, such membranes would crystallize at physiological temperatures

37 Prostaglandins-prostanoids (eicosanoids) A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids. Every prostaglandin contains 20 carbon atoms, including a 5- carbon ring. They are local hormones and have a wide variety of actions: - cause constriction or dilation in vascular smooth muscle cells - cause aggregation or disaggregation of platelets - sensitize spinal neurons to pain - decrease intraocular pressure - regulate inflammatory mediation - regulate calcium movement - control hormone regulation 8 - control cell growth Prostanoic acid

38 Prostaglandins-prostanoids (eicosanoids) Linoleic acid (18:2) acyclic compound Arachidonic acid(20:4) YLXYGENASE aspirine inhibits it LTB 4 (leukotriene) PG keto-PGF 1 (prostacyclin) PGF 2 (prostaglandin) TXB 2 (thromboxane) yclic compounds

39 Saponification number the highest mass of a triglyceride, the lowest saponification number defined as the number of milligrams of K needed to neutralize the fatty acids in 1 gram of fat butter (large proportion of short chain FAs) sap. no oleomargarine (long chain FAs) sap. No is 195 or less K K K K g tripalmitin g K 1 g - x x = 0,208 g = 208,4 mg

40 3 Iodine number measures the degree of unsaturation in a given amount of fat or oil the iodine number is the number of grams of iodine absorbed by 100 grams of fat ottonseed oil: live oil: Linseed oil: frequently used to determine adulteration of commercial lots of oils (older fats have lower iodine numbers) 854 g glyceride g iodine g - x ( 2 ) 7 x = 119,9 g 2 2 ( 2 ) ( 2 ) I I I I I I 2 2 ( 2 ) I 2 dioksan I ( 2 ) 7 I ( 2 )

41 1. The compound given below, in which R 1 and R 2 are rests of fatty acids, is called: A. α-lecithin B. α-cephalin. Prostaglandin D. β-cephalin 2. The following trigliceride contains rests of: A. saturated fatty acids only B. unsaturated fatty acids only. 2 saturated rests and 1 unsaturated D. 2 unsaturated rests and 1 saturated R _ P R N( 3 ) 3 3. omplete the missing organic compounds: Na A , Na, B , Na, , Na, D , Na, Ni... 3.