L I P I D S

L I P I D S1What is lipid?

any of a group of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.Lipids can be more formally defined as substances such as a fat, oil or wax that dissolves in alcohol but not in water. Lipids contain carbon, hydrogen and oxygen but have far less oxygen proportionally than carbohydrates. Lipids are an important part of living cells. Together with carbohydrates and proteins, lipids are the main constituents of plant and animal cells. 2

fatty acids are classified as saturated and unsaturated according to whether they have carbon-carbon double bonds or not.The carbon-carbon double bonds are sites where the molecules are not saturated with hydrogen and are susceptible to chemical attack3Element bromine (Br2) is a substance that eagerly attacks these double bonds. The product of this reaction is a brominated fatty acid.

4OBJECTIVES To be able to classify substances which are insoluble in water in any organic solvents.5 To be able to determine the degree of unsaturated of lipids. To be able to determine the cleansing power of soap and detergents Test for SolubilitySampleSolvent UsedResultCottonseed OilDistilled water3 secs, insolubleEthyl alcohol2-3 secs, solubleEther2-3 secs, solubleChloroform2-3 secs, solubleBenzene2- 3 secs soluble5 % hydrochloric acid3 secs, insoluble5 % sodium hydroxide3 secs, insolubleDiscussionLipids are soluble only in nonpolar solvents because lipids, themselves, are nonpolar. Water, 5 % hydrochloric acid, 5 % sodium hydroxide are polar; Ethyl alcohol ether, chloroform, and benzene are not.

Test for UnsaturationSampleSolvent UsedReagent AddedResultOleic AcidDistilled waterBromine in CCl4The color orange fainted after 8 dropsPalmitic AcidEthyl alcoholChloroformHanus IodineFrom color light pink to yellow (24:44 mins)Oleic AcidEtherChloroformHanus IodineColor light pink to yellow(28 mins)Cottonseed OilChloroformChloroformHanus IodineLight pink to color yellowDiscussion

Test for unsaturation identifies the level of saturation and the number of bonds a lipid has. The more unsaturated, multi-bond the lipid is, the more it absorbs iodine. The less iodine it absorbs, it considered to be saturated, single bonded.Acrolein TestSampleSolvent UsedReagent AddedResultGlycerol Distilled waterKHSO4Odor is pungentPalmitic AcidCottonseed oilKHSO4Odor is pungent DiscussionThe purpose of acrolein test is to find out whether there is a presence of glycerin or fats in a compound. The way to perform this test is to heat a sample with potassium bisulfate (KHSO4) If acrolein is released, then the test is positiveWhen a fat is heated strongly in the presence of adehydrating agent such as KHSO4, the glycerol portion of the molecule is dehydrated to form the unsaturated aldehyde, acrolein (CH2=CH-CHO), which causes a pungent odor.Test for RanciditySampleReagent AddedResultFresh coconut oil

PhenolphthaleinTransparent color and two layers formedMethyl OrangeColor light orange and formed two layersRancid coconut oil

pH paperDid not change in colorPhenolphthaleinBrownish yellow with two layersDiscussionRancidity is a term generally used to denote unpleasant odors and flavors in foods resulting from weakening in the fat or oil portion of a food.

SaponificationSampleReagent AddedResultCoconut Oil

10 % KOHBubble formation and jelly-like substanceDiscussionSaponification is a process by which triglycerides are reacted with sodium or KOH to produce glycerol and a fatty acid salt that is called 'soap'. Lipids that contain fatty acid ester linkages can undergo hydrolysis. This reaction is catalyzed by a strong acid or base. Saponification is the alkaline hydrolysis of the fatty acid esters.

A positive test is indicated by:

Formation of bubbles

- which indicates that a soap was formed

a negative test (left) and a positive test (right)19Properties of Soap Salting OutSampleReagent AddedResultSoap Solution

NaClCrystal formation and white substance was formed and it has a coconut odor20SampleReagent AddedResultSoap Solution

10 % HClA thicke white precipate formedFormation of Fatty AcidsDetergent5 % CaCl2It became cloudy5 % MgCl2

21SampleReagent AddedResultSoap Solution

5 % CaCl2A thick white precipitate formed5 % MgCl2Slight clear white color formedInsoluble SoapsDetergent5 % CaCl2It became cloudy5 % MgCl2

22SampleReagent AddedResultDetergent

5 % CaCl2It became cloudy5 % MgCl2It became cloudy23DiscussionCarboxylic acids and salts show signs of unusual behavior in water due to the presence of both hydrophilic (CO2) and hydrophobic (alkyl) regions in the same molecule. Such molecules are termedamphiphilic(Gk. amphi = both) oramphipathic.Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water.SampleReagent AddedResultCholesterol

CHCl2AceticAnhydrideConc. H2SO4Orange color then after 2 mins, color changed to blueLiebermann Burchard Test for CholesterolDetergent5 % CaCl2It became cloudy5 % MgCl2

25DiscussionThis testis used for the detection ofcholesterol. The formation of a green or green-blue colour after a few minutes is positive. The colour is due to the hydroxyl group (-OH) of cholesterol reacting with the reagents and increasing the conjugation of the un-saturation in the adjacent fused ring.Emulsifying Action of LecithinSampleReagent AddedResult2 % AlbuminCholesterolWhite color that is slightly thickCholesterol LecithinYellowish white color that is thick2 % AlbuminCholesterolWhite color that is slightly thickCholesterol LecithinYellowish white color that is thickDiscussionLecithin, a lipid material composed of choline and inositol, is found in all living cells as a major component of cell membranes, which regulate the nutrients entering and exiting the cell.Answers to Questions:Why are fatty acids insoluble in water?

Because they are hydrophobic that is lack of infinity of water, and fatty acids are having a long hydrocarbons chain, making it not insoluble in water.

The hydrocarbons chain can be also called as tail which shows hydrophobic properties due to the chain ( as the number of hydrocarbons increases, its solubility in water decreases. ) And water is polar compound and hydrocarbons are non-polar and as like dissolved like. (there are some exceptions.) because, fatty acids are soluble only in fats.29The hydrocarbons chain can be also called as tail which shows hydrophobic properties due to the chain ( as the number of hydrocarbons increases, its solubility in water decreases. ) And water is polar compound and hydrocarbons are non-polar and as like dissolved like. (there are some exceptions.) because, fatty acids are soluble only in fats.

302. Explain why the cis-form is the predominant configuration of unsaturated fatty acids?

Trans forms are often more thermodynamically stable (lower in energy) than cis and might be expected to predominate except that the two are not formed in a random manner31Such compounds are usually formed in bio-chemically important reactions involving enzymes which often only produce one of the possible isomers that could be formed. If the cell has a use for the cis isomer only then is likely that it will have evolved enzymes that will produce the cis form exclusively. 32Because if the double bond is a cis bond the carbon atoms are on the same side this causes a spontaneous breaking in the chain allowing different and more rigid shapes to be formed. 33A trans bond has a carbon atoms on opposite sides leaving the structure similar to the saturated form, trans fatty acids are generally a product of processing ( hydrogenation ) that no usual found naturally making it difficult to invent properly.343. What type of rancidity occurs in vegetable shortenings? How can it be prevented?

The type of rancidity that occurs in vegetable shortenings is oxidative rancidity.

354. Show the structure of the parent compound of cholesterol.

Cholesterol is a parent compound of practically every steroid in your body.cholestrol is a steroid, which has 4 rings of carbon, 3 6-carbon rings and a 5 carbon ring, fused together, and on one end has a 8 carbon hydrocarbon, and an OH on the other..36

Structure of Cholesterol375. Explain the cooperative effect of lecithin and albumin.

Lecithin is an emulsifier consisting of a variety of ingredients, the active components being phospholipids - these are long chain polar lipids. 38The emulsifying properties of lecithin result from this combination of a polar (hydrophilic) group attached to a non-polar (hydrophobic) lipid chain, and means that they can help disperse an oil phase into an aqueous solution or vice versa, creating an emulsion (oil-in-water or water-in-oil respectively). 39These emulsions are not solutions, but rather are very well dispersed micro-droplets of the secondary phase, and this explains why emulsions are opaque rather than completely transparent, Albumins are water-soluble proteins a - massive polar moleculesConclusion:We therefore conlude that, Lipids are a family of substances that are insoluble in water but soluble in nonpolar solvents and solvents of low polarity, such as diethyl ether. It functions as Energy Storage; Membrane Components and Messengers.

Classified into different groups: Complex lipids,Fats, Steroids, Prostaglandins, Thromboxanes and Lukotrienes.http://www.australianolives.com.au/assets/files/pdfs/Media/Health%20Effects%20of%20Rancid%20Oils.pdfhttp://chemistry.about.com/library/glossary/bldef825.htmhttp://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/food/sapon/sapon.htm