Lipids. Functions. 1. Store energy: fat cells Thermal blanket. 2. Chemical messengers: find in nerve fibers and hormones.

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

3 Lipids Functions 1. Store energy: fat cells Thermal blanket 2. hemical messengers: find in nerve fibers and hormones. 3. Parts of membranes: insoluble in water 4. Precursors of hormones (steroids and prostaglandins)

4 Lipids There are 2 types of lipids; those that contain the structural component of a fatty acid; and those that contain the structural component of a four member steroid molecule.

5 Lipids with fatty acids Lipids 1. Simple lipids: Triglycerides (Fats & ils), Waxes Store energy, insulation 2. omplex lipids Glycerophospholipids Sphingolipids ell membrane 3. Eicosanoids Pain, fever, inflammation Lipids without fatty acids Steroids (holesterol & steroid hormones) hemical messenger ell membrane

6 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)

7 Lipids Lipids can be categorized as: 1. Hydrolyzable lipids can be converted into small molecules by aqueous hydrolysis.

8 Lipids Lipids can be categorized as: 2. Nonhydrolyzable lipids cannot be cleaved into smaller molecules by aqueous hydrolysis.

9 Hydrolysis Most hydrolyzable lipids contain an ester. Hydrolysis: reaction with water. (breaking a bond and adding the elements of water) RR' An ester Heat R- H + H 2 + H + or enzyme A carboxylic acid H-R' An alcohol

10 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

11 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: H H H Stearic aci (mp 70 leic acid (mp 16 Linoleic ac (mp-5 n H 2n+1 H n - carbon atoms in a molecule H Linolenic a (mp -1

12 Nomenclature of fatty acids SATURATED FATTY AIDS ommon name Systematic name Formula 4:0 Butyric Butanoic acid 3 H 7 H 6:0 aproic acid Hexanoic acid 5 H 11 H 8:0 aprylic acid ctanoic acid 7 H 15 H 10:0 apric acid Decanoic acid 9 H 19 H 12:0 Lauric acid Dodecanoic acid 11 H 23 H 14:0 Myristic acid Tetradecanoic acid 13 H 27 H 16:0 Palmitic acid Hexadecanoic acid 15 H 31 H 18:0 Stearic acid ctadecanoic acid 17 H 35 H 20:0 Arachidic Eicosanoic acid 19 H 39 H 24:0 Lignoceric acid Tetracosanoic acid 23 H 47 H

13 16:0 Palmitic acid (15H31H) Structural formula of palmitic acid H 3 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H H 3 (H 2 ) 14 H ondensed structural formula of palmitic acid H Skeletal formula of palmitic acid

14 Fatty acids Hydrolyzable lipids are derived from fatty acids. Fatty acids are: Long-chain unbranched carbon attached to a carboxyl group (-H). Typically carbon atoms. They have an even number of atoms. Insoluble in water. is H H H H Stearic aci (mp 70 leic acid (mp 16 Linoleic ac (mp-5 Linolenic a (mp -1 H H Steari (m leic (mp H Linole

15 Fatty acids H 3 (H 2 ) 14 H (palmitic acid) polar portion = hydrophillic nonpolar portion = hydrophobic Hydrophobic portion is much bigger than hydrophilic portion. Insoluble in water

16 Saturated and unsaturated Fatty acids Saturated fatty acids have no double bonds in their long hydrocarbon chains. Stearic acid: H 3 (H 2 ) 16 H They are solids at room temperature. Packed together H H H H H

17 Saturated and unsaturated Fatty acids Unsaturated fatty acids have 1 or more double bonds (generally cis) in their long hydrocarbon chains. leic acid: H 3 (H 2 ) 7 H=H(H 2 ) 7 H They are liquids at room temperature. Kinks They can not pack together H H H H H

18 Unsaturated fatty acids Various conventions are in use for indicating the number and position of the double bond(s) In chemistry n (Δ) designation: Δ = delta 18 H 3 (H 2 ) 7 H 18:1,9 or 9 18: H(H 2 ) 7 H arbon atom numbering starts from H group In biochemistry: ω designation ω = omega H 3 H 2 H 2 H 2 H 2 H 2 H 2 H 2 H H(H 2 ) 7 H n , 18:1 or n-9, 18: arbon atom numbering starts from H 3 group

19 Fatty acids The human body is capable of synthesizing most fatty acids from carbohydrates or other fatty acids. Humans do not synthesize sufficient amounts of fatty acids that have more than one double bond. More than one double bond fatty acids are called essential fatty acids and they must be provided by the diet. Linoleic acid Linolenic acid

20 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 H 3 group). LINLEI AID 18:2 (9,12) is main representative acid of this group H 3 1 (H 2 ) 4 H 6 H 7 H 2 8 H H 9 10 (H 2 ) 7 H 18 (mega 3) Fatty acids that contain at least two double bonds, one of them at 3 (starting from H 3 group) LINLENI AID 18:3 (9,12,15) is the basic acid of this group H 3 1 H 2 2 H 3 H 4 H 2 5 H 6 H 7 H 2 H H (H 2 ) 7 H 18

21 Essential Fatty acids mega-n acids n: the position of the first double bond Linoleic acid is called an omega-6 acid, because of the position of the first = in the nonpolar chain. carbon atom numbering starts from H 3 group

22 Essential Fatty acids Linolenic acid is called an omega-3 acid, because of the position of the first = in the nonpolar chain.

23 mega-3 sources: Flaxeed oil/canola oil Fish liver oils/fish eggs Human Milk Seafood/Fatty fish - albacore tuna - mackerel - salmon -sardines mega-6 sources: orn oil Peanut oil ottonseed oil Soybean oil Many plant oils Proper n-6 to n-3 ratio in a diet is 4:1

24 Fatty acids 3 H 7 H butyric acid (butanoic acid) short chain FA ommon medium-chain saturated fatty acids: 5 H 11 H caproic acid (hexanoic acid) 7 H 15 H caprylic acid (octanoic acid) 9 H 19 H capric acid (decanoic acid) H 2 5 H 3 6 H 2 4 H 2 3 H 2 2 H 1 caproic acid liquid (1 to 6), solid (from 7)

25 Fatty acids common long-chain saturated FA s: 11 H 23 H : lauric acid (n-dodecanoic acid; 12:0 ) 13 H 27 H : myristic acid (n-tetradecanoic acid; 14:0 ) 15 H 31 H : palmitic acid (n-hexadecanoic acid; 16:0 ) 17 H 35 H; stearic acid (n-octadecanoic acid; 18:0 ) 19 H 39 H; arachidic (eicosanoic acid; 20:0 ) 23 H 47 H; lignoceric acid 25 H 51 H; cerotic acid

26 iso isobutyric acid Less common fatty acids H 3 H 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 (H 2 ) 12-2 H R= H H 3 H 3 R (H 2 ) 10-2 H chaulmoogric acid hydnocarpic acid

27 MonoUnsaturated fatty acids MUFA Monoenoic acid (monounsaturated) n H 2n-1 H 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. H 3 18 (H 2 ) 6 H 2 11 H 2 8 (H 2 ) 6 H H H leic acid 18:1 n-9(cis) or 18:1 (Δ9) H hemical formula 18 H H 33 H Elaidic acid 18:1 (9trans)

28 Unsaturated fatty acids Dienoic acid: linoleic acid 18:2 (9cis, 12cis) H 3 (H 2 ) 4 H=H H 2 H=H (H 2 ) 7 H hemical formula 18 H H 31 H cis linoleic acid Trienoic acid: linolenic acid 18:3 (9cis, 12cis, 15cis)

29 PolyUnsaturated fatty acids PUFAs Polyenoic acid (polyunsaturated, tetranoic acid) H H 3 Arachidonic acid 20:4 (Δ 5,8,11,14) PUFAs are fatty acids that contain more than one double bond in their backbone

30 UNSATURATED FATTY AIDS leic acid 18:1 ω-9 cis Δ 9 Elaidic acid 18:1 ω-9 trans Δ 9 Linoleic acid (LA) 18:2 ω-6 cis Δ 9,12 γ-linolenic acid (GLA) 18:3 ω-6 cis Δ 6,9,12 α-linolenic (ALA) 18:3 ω-3 cis Δ 9,12,15 Arachidonic acid 20:4 ω-6 cis Δ 5,8,11,14 Eicosapentaenoic acid (EPA) 20:5 ω 3 cis Δ 5,8,11,14,17 Docosahexaenoic acid (DHA) 22:6 ω 3 cis Δ 4,7,10,13,16,19 18 H 9 H 3 -(H 2 ) 7 -H=H-(H 2 ) 7 -H 18 H 3 -(H 2 ) 7 -H=H-(H 2 ) 7 -H H H H 3 -(H 2 ) 4 -(H=H-H 2 ) 2 -(H 2 ) 6 -H H 3 -(H 2 ) 4 -(H=H-H 2 ) 3 -(H 2 ) 3 -H 18 H H 3 -H 2 -(H=H-H 2 ) 3 -(H 2 ) 6 -H H H H 3 -(H 2 ) 4 -(H=H-H 2 ) 4 -(H 2 ) 2 -H H H 3 -H 2 -(H=H-H 2 ) 5 -(H 2 ) 2 -H H 3 -H 2 -(H=H-H 2 ) 6 -H 2 -H H

31 omparison of melting points Melting Points of Saturated vs. Unsaturated Fatty Acids: the unsaturated fatty acids have lower melting points than the saturated fatty acids. The molecular structure allows many fatty acid molecules to be rather closely "stacked" together. lose intermolecular interactions result in relatively high melting points. The introduction of one or more double bonds in the hydrocarbon chain in unsaturated fatty acids results in one or more "bends" in the molecule. These molecules do not "stack" very well. The intermolecular interactions are much weaker than saturated molecules. As a result, the melting points are much lower for unsaturated fatty acids.

32 omparison of melting points Melting Points of Saturated vs. Unsaturated Fatty Acids: the unsaturated fatty acids have lower melting points than the saturated fatty acids.

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

34 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.

35 Waxes Wax is an ester of saturated fatty acid and long chain alcohol. Long-chain alcohol Long-chain alcohol Ester bond Fatty acid Acid

36 Waxes Because of their long nonpolar chains, waxes are very hydrophobic. Beeswax (myricyl palmitate) H 3 (H 2 ) 14 hydrophobic region (H 2 ) 29 H 3 hydrophobic region They form protective coatings: - In plants, they help prevent loss of water and damage from pests. - In humans and animals, provide waterproof coating on skin and fur.

37 Beeswax arnauba oating Jojoba Lanolin from wool lotions

38 Waxes Hydrolysis reaction: like other esters, waxes are hydrolyzed. Heat

39 Soaps Hydrophobic part: nonpolar a soap is a salt of a fatty acid Hydrophilic part: polar (remains in contact with environment) 3 R - Na + n) Sodium soaps

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

41 Soaps When soap is mixed with dirt (grease, oil, and ), soap micelles dissolve these nonpolar, water-insoluble molecules.

42 hard -sodium soaps e.g. soap bar 17 H 35 - Na + water soluble Soaps water insoluble -barium, magnesium, calcium soaps ( 15 H 31 ) 2 Ba Soaps don t work effectively in hard water! soft -potassium soaps, e.g shampoo, shaving soaps, liquid soaps 17 H 35 - K + polar hydrophilic carboxylate group - nonpolar hydrophobic hydrocarbon chain e.g. stearate 17 H 35 - Amphipatic (amphiphilic) nature of a soap

43 Detergents Synthesis of detergents (H 2 )n-h 3 H 2 S 4 (H 2 )n-h 3 NaH (H 2 )n-h 3 _ n=10-20 S 2 H S 2 Na + alkylbenzene alkylbenzenesulfonic acid sodium salt of alkylbenzenesulfonic acid These substances are usually alkylbenzenesulfonates Polar sulfonate (of detergents) is less likely than the polar carboxylate (of soap) to bind to calcium and other ions found in hard water. Detergents work effectively in hard water their barium or magnesium salts are water soluble

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

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

46 Triglycerides 1-stearoyl-2,3 linoleoyl glyceride

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

48 Triglycerides chemical properties Enzymatic hydrolysis (reaction reversible) a STERESELETIVE reaction H 2 H H 2 R 1 R 2 Triglyceride R 3 + 2H 2 lipase R 1 R 3 H H Fatty acids of carbons 1 i 3 + H 2 H H 2 H H 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.

49 Triglycerides chemical properties Hardening (hydrogenation) H 3 (H 2 ) 7 H H (H 2 ) 7 H 2 (H 2 ) 7 H H H + 3H 2 Ni H 3 (H 2 ) 16 H 2 H (H 2 ) 16 H 3 H 3 (H 2 ) 7 H 2 (H 2 ) 7 H H (H 2 ) 7 H 3 H 2 (H 2 ) 16 H 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

50 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. H 2 H H 2 15 H H H 31 + H 2 H 2 17 H H H 35 H 2 NaH H 17 H 33 H 17 H 33 + H 17 H H H 31 substitute of cocoa butter 1-stearo-2-oleo-3-palmitin H 2 15 H H H 29 It is the source of structured fats. H 2 H SHRT/MEDIUM HAIN FATTY AID MEGA - 3 or -6 FATTY AID H 2 SHRT/MEDIUM HAIN FATTY AID

51 Types of Fatty Acid Lipids phospate phospate Phospholipids

52 Phospholipids Phospholipids are lipids that contain a P atom. Two common types:

53 Phospholipids 1. Phosphoacylglycerols (glycerophospholipids): They are the main component of most cell membranes. Structurally, they resemble a triacylglycerol, except the third fatty acid has been replaced with a phosphodiester bonded to an alcohol. Fatty acid Fatty acid Amino alcohol

54 Phospholipids - main components H 2 H H H H P H H 2 H H Glycerol Phosphoric acid Hydroxyl compounds: H H 2 H H NH 2 serine H + H 2 H 2 NH 3 ethanolamine H H 2 H 2 N + H 3 H 3 H 3 choline H H H H H H inosytol

55 Phospholipids 1. Phosphoacylglycerols: Ethanolamine holine

56 1. Phosphoacylglycerols: Phospholipids 17 H 35 H 2 * H 15 H 31 H 2 P H Ester bond R Their names depending on R: H 2 H H NH 2 + H 2 H 2 NH 3 H 2 H 2 N + H 3 H 3 H 3 Phosphatidylserine (cephaline) Phosphatidylethanolamine (cephaline) Phosphatidylcholine (lecithine)

57 1. Phosphoacylglycerols: Phospholipids phosphoester bond H 2 P + H 2 H 2 N(H 3 ) 3 17 H 35 * H H - phosphatidylcholine ( -lecithine) ester bond H 2 15 H 31 H 3 N + H 2 H 2 P H 2 * H 15 H 31 -phosphatidylethanolamine ( - cephaline) H H 2 15 H 31 hydrophilic hydrophobic Natural phospholipids are L i.

58 2 Plasmalogens Phospholipids - form 10% of brain and muscles phospholipids Ether bond H H H R 1 R 1 rest of an alcohol (mainly unsaturated) R H 2 * H H P H + H 2 H 2 NH 3 ethanolamine R rest of fatty acids Ethalomine Serine holine Inositol Ethanolamine plasmalogen They have anticancer properties.

59 Phospholipids 3. Sphingolipids (Sphingomyelins): They differ in two ways: 1. They do not contain a glycerol backbone, they have a sphingosine backbone instead. sphingosine 2. They do not contain an ester; their single fatty acid is bonded to the backbone by an amide bond.

60 Phospholipids 3. Sphingolipids (Sphingomyelins) The myelin sheath, the coating that surrounds nerve cells, is rich in sphingomyelins.

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

62 Phospholipids 3. Sphingolipids (Sphingomyelins) Sphingomieline

63 Glycolipids erebrosides - is a sphingolipid (ceramide) with a monosaccharide such as glucose or galactose as polar head group. H 3 (H 2 ) 12 H H H H H H sphingosine H H 2 H H H H H H Sugar, e.g. gluctose HN H H 2 (H 2 )H (H 2 ) 21 H 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.

64 omponent Structures of Some Important Membrane Lipids

65 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 H 1 Prostanoic acid

66 Prostaglandins-prostanoids (eicosanoids) Linoleic acid (18:2) acyclic compound H 8 5 H H Arachidonic acid(20:4) H 20 YLXYGENASE aspirine inhibits it LTB 4 (leukotriene) 13 5 H H 1 H PGH 2 H 9 5 H 1 11 H H 6-keto-PGF 1 (prostacyclin) 20 H 9 11 H H 1 H 20 PGF 2 (prostaglandin) H H 21 TXB 2 (thromboxane) yclic compounds

67 Eicosanoids Prostaglandins and Leukotrienes are two types of eicosanoids (20 atoms derived from the fatty acids). - All eicosanoids are very potent compounds, which are not stored in cells, but rather synthesized in response to external stimulus. - Unlike hormones they are local mediators, performing their function in the environment in which they are synthesized.

68 Prostaglandins Prostaglandins are responsible for inflammation. - Aspirin and ibuprofen relieve pain and inflammation by blocking the synthesis of these molecules. - Prostaglandins also decrease gastric secretions, inhibit blood platelet aggregation, stimulate uterine contractions, and relax smooth muscles. - There are two different cylcooxygenase enzymes responsible for prostaglandin synthesis called X-1 and X-2.

69 Prostaglandins X-1 is involved in the usual production of prostaglandins. X-2 is responsible for additional prostaglandins in inflammatory diseases like arthritis. - Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen inactivate both X-1 and -2, but increase risk for stomach ulcer formation. - Drugs sold as Vioxx, Bextra, and elebrex block only the X-2 enzyme without affecting gastric secretions.

70 Leukotrienes Asthma is characterized by chronic inflammation, so inhaled steroids to reduce this inflammation are commonly used. Leukotrienes are molecules that contribute to the asthmatic response by constricting smooth muscle of the lung. New asthma drugs act by blocking the synthesis of leukotriene 4, which treat the disease instead of just the inflammation symptoms.

71 Steroids Steroids have: A steroid nucleus which is 4 carbon rings. Attached groups that make the different types of compounds. No fatty acids. (steroid nucleus)

72 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 H 3 groups R 3 hydrocarbon chain of different length sterols steroids contaning -H group in the 3 position

73 H 3 x holesterol and cholesterol esters H 3 x 10 5 x 6 x H 3 H 2 H 2 H 3 x H 2 H H 3 H 3 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 H 3 H 2 H 3 H 3 H 3 H 3 H 3 H 3 H 3 H 3 H 3 H 3 H 3 H -Sitosterol (phytosterol, in plants) (to progesteron production) H Ergosterol, in fungi (to vit. D2 production)

74 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

75 holesterol holesterol: Is the most abundant steroid in the body. Insoluble in water (need a water soluble carrier). Has methyl H 3 - groups, alkyl chain, and -H attached to the steroid nucleus. H 3 H 3 H 3 H 3 H 3 H

76 Lipoproteins Triacylglycerols Water-soluble form of lipids (soluble in blood) Spherical particles Polar surface and nonpolar inner Transporting lipids through the bloodstream to tissues where they are stored, Used for energy, or to make hormones.

77 Lipoproteins VLDL: very-low-density lipoprotein Triglycerides and holesterol LDL: low-density lipoprotein (bad holesterol) holesterol HDL: high-density lipoprotein (good holesterol) holesterol Recommended levels are: HDL > 40 mg/dl, LDL < 100 mg/dl, total serum cholesterol < 200 mg/dl. hylomicrons Triglycerides and holesterol VLDL Intestine and elimination Liver Fat storage cells LDL HDL Heart and muscles Energy

78 Steroid Hormones A hormone is a molecule that is synthesized in one part of an organism, which then elicits a response at a different site. Two types of steroids hormones: 1. Sex hormones Estrogens & progestins in females Androgens in males 2. Adrenal ortical Steroids

79 Sex Hormones Estrogens (Female Sex Hormones): The estrogens estradiol and estrone control development of secondary sex characteristics, regulate the menstrual cycle, and are made in the ovaries.

80 Sex Hormones Progestins (Female Sex Hormones): The progestin progesterone is called the pregnancy hormone ; it is responsible for the preparation of the uterus for implantation of a fertilized egg.

81 Sex Hormones Androgens (Male Sex Hormones): Testosterone and Androsterone are androgens made in the testes. They control the development of secondary sex characteristics in males.

82 Adrenal ortical Steroids Aldosterone regulates blood pressure and volume by controlling the concentration of Na + and K + in body fluids. ortisone and cortisol serve as anti-inflammatory agents, which also regulate carbohydrate metabolism. aldosterone cortisone cortisol

83 Vitamins They are organic compounds required in small quantities for normal metabolism. They must be obtained from the diet (our cells cannot synthesize them). Vitamins are either water soluble or fat soluble. The four fat-soluble vitamins (A, D, E, and K) are lipids and nonpolar. They are found in fruits, vegetables, fish, liver, and dairy products. Excess vitamins are stored in adipose cells to be used when needed.

84 Vitamins Vitamin A It is found in liver, fish, and dairy products, and is made from β-carotene (the orange pigment in carrots). It is needed for vision and for healthy mucous membranes. Vitamin A deficiency causes night blindness and dry eyes and skin.

85 Vitamins Vitamin D Vitamin D can be synthesized from cholesterol. It is produced in the skin on exposure to UV radiation It can be obtained in the diet from many foods, especially milk, and helps regulate a and P metabolism. Is necessary for normal bone growth and function. A deficiency of vitamin D causes rickets (bone malformation).

86 Vitamins Vitamin E Vitamin E is an antioxidant, protecting unsaturated side chains in fatty acids from unwanted oxidation. Deficiency of vitamin E causes numerous neurological problems, although it is rare.

87 Vitamins Vitamin K Vitamin K regulates the synthesis of clotting proteins (prothrombin), and deficiency of this leads to excessive or fatal bleeding.

88 Schematic Diagram of a ell Membrane The phospholipid bilayer with embedded cholesterol and protein molecules. Short oligosaccharide chains are attached to the outer surface.

89 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 HARATER 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

90 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

91 Saponification number the highest mass of a triglyceride, the lowest saponification number defined as the number of milligrams of KH 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 H H 2 15 H 31 K H H + 3 KH H H 2 H H H H 2 15 H 31 H K H 2 H 806 g tripalmitin g KH 1 g - x x = 0,208 g = 208,4 mg

92 Iodine number H 3 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 H g - x (H 2 ) 7 x = 119,9 g H H H H 2 H H H 2 H (H 2 ) 7 H 3 H 2 H 2 (H 2 ) 7 H H 15 H 31 I I I I I I H H H H 2 H H H 2 H H (H 2 ) 7 H 2 H + 4I 2 dioksan I (H 2 ) 7 H I H (H 2 ) 7 H 3 H 2 15 H 31

93 Thank You