LIPIDS
- 1. LIPIDS
- 2. Course Contents • Functions of lipids • structure of lipids • Properties of Lipids • Biological significance of Lipids • Classifications of Lipids – 1. Simple lipids – 2. Compound Lipids – 3. Derived Lipids • Fatty Acids • Fats & oil • .
- 3. • Saturated and unsaturated fatty acids • Uses of fats in the body • Physical and chemical properties of fats • Role of phospholipids in cell membranes. • Role of steroids (cholesterol ) • Distinguish between soap and detergents
- 4. • Hydrophobic • amphiphilic • small molecules the amphiphilic nature of some lipids allows them to form structures such as • Vesicles • Liposomes • membranes in an aqueous environment Lipids
- 5. Examples • Fats • Waxes • Sterols • fat-soluble vitamins – (such as vitamins A, D, E, and K) • Glycerides – Monoglycerides – Diglycerides – Triglycerides • phospholipids.
- 6. • Functions • Source of heat and energy • structural components of cell membranes • signaling molecules • Insulation for the organs and nerves • Regulator of fat soluble vitamins • Source of essential fatty acids • Lipids regulate membrane permeability. • They act electrical insulators to the nerve fibres, where the myelin sheath contains lipids. • Lipids are components of some enzyme systems. • Some lipids like prostaglandins and steroid hormones act as cellular metabolic regulators.
- 7. • Cholesterol is found in cell membranes, blood, and bile of many organisms. • Layers of fat in the subcutaneous layer, provides insulation and protection from cold. Body temperature maintenance is done by brown fat. • Polyunsaturated phospholipids are important constituents of phospholipids, they provide fluidity and flexibility to the cell membranes. • Lipoproteins that are complexes of lipids and proteins, occur in blood as plasma lipoprotein, they enable transport of lipids in aqueous environment, and their transport throughout the body. • Cholesterol maintains fluidity of membranes by interacting with lipid complexes. • Cholesterol is the precursor of bile acids, Vitamin D and steroids. • Essential fatty acids like linoleic and linolenic acids are precursors of many different types of ecosanoids including prostaglandins, thromboxanes. These play a important role in pain, fever, inflammation and blood clotting.
- 8. Biological functions • Membranes • The glycerophospholipids are the main structural component of biological membranes, such as the cellular plasma membrane and the intracellular membranes of organelles
- 9. • Energy storage • Triglycerides, stored in adipose tissue, are a major form of energy storage both in animals and plants. • The complete oxidation of fatty acids provides high caloric content, about 9 kcal/g, compared with 4 kcal/g for the breakdown of carbohydrates and proteins.
- 10. •Signaling • In recent years, evidence has emerged showing that lipid signaling is a vital part of the cell signaling
- 11. •Other functions • The "fat-soluble" vitamins (A, D, E and K) – are essential nutrients stored in the liver and fatty tissues, with a diverse range of functions.
- 12. • fats are a subgroup of lipids called triglycerides. • Lipids also encompass molecules such as –fatty acids and their derivatives –sterol-containing metabolites such as cholesterol Fats vs lipids
- 13. Fats vs oil Fats Oil solid at room temperature Fats that are liquid at room temperature saturated unsaturated
- 14. Fats vs Oil • The triesters of fatty acids with glycerol (1,2,3- trihydroxypropane) compose the class of lipids known as fats and oils. These triglycerides (or triacylglycerols) are found in both plants and animals, and compose one of the major food groups of our diet. Triglycerides that are solid or semisolid at room temperature are classified as fats, and occur predominantly in animals.
- 15. Fats • Esters of fatty acids with glycerol solid at room temperature.
- 16. Oil • Oils are fats in the liquid state at room temperature. Because they contain unsaturated fatty acids.
- 17. Classification
- 19. Simple lipids • A simple lipid is a fatty acid ester of different alcohols and carries no other substance. These lipids belong to a heterogeneous class of predominantly nonpolar compounds, mostly insoluble in water, but soluble in nonpolar organic solvents such as chloroform and benzene.
- 21. Complex lipids • Lipids combined with carbohydrates, proteins, aminoacids, phosphates or other non lipid compounds. • Glycolipids • Phospholipids • Lipoproteins etc.
- 22. Derived lipids • These are substances derived from simple lipids and compound lipids by hydrolysis. They also, include substances related to lipids. • Derived lipids include: • 1- Fatty acids • 2- Glycerol • 3- Steroids • 4- Isoprenoids • 5- prostglandins and leukotriens derived from arachidonic acid.
- 23. Advanced classification • lipids may be divided into eight categories: . fatty acids • Glycerolipids • Glycerophospholipids • Sphingolipids • Saccharolipids • polyketides • sterol lipids • prenol lipids
- 25. Fatty acids
- 26. there is the possibility of either a cis or a trans geometric isomerism, Cis-double bonds cause the fatty acid chain to bend, an effect that is more pronounced the more double bonds there are in a chain. This in turn plays an important role in the structure and function of cell membranes • Most naturally occurring fatty acids are of the cis configuration
- 27. properties • decompose into glycerol and fatty acids. • float on water • insoluble in water • greasy to the touch • lubricating • not readily volatile • burn without leaving any residue, i.e., ash. • Low density, low mp, bp.
- 28. Hydrogenation • This process has a vital role in the fats and oils industry because it achieves two main goals. • Firstly, liquid oils into semisolid fats • secondly, improved stability.
- 29. auto-oxidation and rancidity • Unsaturated fatty acids undergo a chemical change known as auto-oxidation. • The process requires oxygen (air) and is accelerated by the presence of trace metals. • Vegetable oils resists this process because they contain • antioxidants, such as tocopherol
- 30. • Trans fats and oils have higher melting points than cis ones because the packing isn't affected quite as much. Naturally occurring unsaturated fats and oils tend to be the cis form.
- 31. Fatty acids • hydrocarbon with a carboxylic acid group; • polar, hydrophilic end, and a nonpolar, hydrophobic end • chain, typically between 4 and 24 carbons • may be saturated or unsaturated, • and may be attached to functional groups
- 32. Triglycerides • A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids.
- 33. Waxes • Esters of fatty acids with high molecular weight monohydroxy alcohols. Example: Beeswax, Carnauba wax.
- 34. Phospholipids • Phospholipids or Phosphatids are compound containing fatty acids and glycerol in addition to a phosphoric acid, nitrogen bases and other substituents. Phospholipids can be phosphoglycerides, phosphoinositides and phosphosphingosides.
- 35. Steroids • Steroids comprise a group of cyclical organic compounds whose basis is a characteristic arrangement of seventeen carbon atoms in a four-ring structure linked together from three 6-carbon rings followed by a 5-carbon ring and an eight- carbon side chain on carbon 17
- 36. Sterol (a steroid sub group) • Sterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules.
- 37. Cholesterols (A sterol) • a compound of the sterol type found in most body tissues, including the blood and the nerves.
- 38. Uses of fats in the body • A healthy body needs some fat, which contains essential nutrients. Your body uses dietary fat to make tissue and manufacture biochemicals, such as hormones. Fats in your diet are sources of energy that add flavor to food — the sizzle on the steak, you can say. However, fats may also be hazardous to your health.
- 39. • Provides a source of stored energy Gives shape to your body Cushions your skin (imagine sitting in your chair for a while as you enjoy your visit to Dummies.com without your buttocks to pillow your bones) Acts as an insulation blanket that reduces heat loss • Part of every cell membrane (the outer skin that holds each cell together)
- 40. • A component of myelin, the fatty material that sheathes nerve cells and makes it possible for them to fire the electrical messages that enable you to think, see, speak, move, and perform the multitude of tasks natural to a living body; brain tissue also is rich in fat • A shock absorber that protects your organs (as much as possible) if you fall or are injured • A constituent of hormones and other biochemicals, such as vitamin D and bile
- 41. Physical and chemical properties of fats • Pure fats and oils are colorless, odorless, and tasteless. • The characteristic colors, odors, and flavors that we associate with some of them are imparted by foreign substances that are lipid soluble and have been absorbed by these lipids. • Fats and oils are lighter than water, having densities of about 0.8 g/cm3. • .
- 42. • They are poor conductors of heat and electricity and therefore serve as excellent insulators for the body, slowing the loss of heat through the skin. • Fats and oils can participate in a variety of chemical reactions—for example, because triglycerides are esters, they can be hydrolyzed in the presence of an acid, a base, or specific enzymes known as lipases. The hydrolysis of fats and oils in the presence of a base is used to make soap and is called saponification
- 43. Role of phospholipids in cell membranes. • Phospholipids form the basic structure of a cell membrane, called the lipid bilayer. http://www.rsc.org/Education/Teachers/Resources/cfb/images/09A.jpg November 11, 2015
- 44. Role of steroids (cholesterol ) • The body makes cholesterol in the liver and uses it for a variety of important functions, ranging from maintaining healthy cell membranes to building crucial hormones and vitamins. • Cholesterol is an essential lipid constituent of cell membranes • Cholesterol is a precursor of steroid hormones and of bile acids
- 45. • Intermediates of cholesterol biosynthesis are required to make vitamin D and for posttranslational modification of membrane proteins • High plasma cholesterol promotes atherosclerosis • Scattered in the lipid bilayer are cholesterol molecules, which help to keep the membrane fluid consistent.
- 46. Distinguish between soap and detergents. • Carboxylic acids and salts having alkyl chains longer than eight carbons exhibit unusual behavior in water due to the presence of both hydrophilic (CO2) and hydrophobic (alkyl) regions in the same molecule. Such molecules are termed amphiphilic (Gk. amphi = both) or amphipathic. • 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.
- 47. • fatty acids spread evenly over an extended water surface, eventually forming a monomolecular layer in which the polar carboxyl groups are hydrogen bonded at the water interface, and the hydrocarbon chains are aligned together away from the water. • Substances that accumulate at water surfaces and change the surface properties are called surfactants.
- 48. • Alkali metal salts of fatty acids are more soluble in water than the acids themselves, and the amphiphilic character of these substances also make them strong surfactants. • The most common examples of such compounds are – soaps and detergents. – The use of such compounds as cleaning agents is facilitated by their surfactant character, which lowers the surface tension of water, allowing it to penetrate and wet a variety of materials.
- 49. • Very small amounts of these surfactants dissolve in water to give a random dispersion of solute molecules. However, when the concentration is increased an interesting change occurs. The surfactant molecules reversibly assemble into polymolecular aggregates called micelles. By gathering the hydrophobic chains together in the center of the micelle, disruption of the hydrogen bonded structure of liquid water is minimized, and the polar head groups extend into the surrounding water where they participate in hydrogen bonding. These micelles are often spherical in shape, but may also assume cylindrical and branched forms, as illustrated on the right. Here the polar head group is designated by a blue circle, and the nonpolar tail is a zig-zag black line.
- 50. • Micelles are able to encapsulate nonpolar substances such as grease within their hydrophobic center, and thus solubilize it so it is removed with the wash water. Since the micelles of anionic amphiphiles have a negatively charged surface, they repel one another and the nonpolar dirt is effectively emulsified. To summarize, the presence of a soap or a detergent in water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble dirt by incorporation in micelles.
- 51. • The oldest amphiphilic cleaning agent known to humans is soap. Soap is manufactured by the base-catalyzed hydrolysis (saponification) of animal fat. • Before sodium hydroxide was commercially available, a boiling solution of potassium carbonate leached from wood ashes was used. • Soft potassium soaps were then converted to the harder sodium soaps by washing with salt solution. • The importance of soap to human civilization is documented by history, but some problems associated with its use have been recognized. One of these is caused by the weak acidity (pKa ca. 4.9) of the fatty acids. Solutions of alkali metal soaps are slightly alkaline (pH 8 to 9) due to hydrolysis. If the pH of a soap solution is lowered by acidic contaminants, insoluble fatty acids precipitate and form a scum. A second problem is caused by the presence of calcium and magnesium salts in the water supply (hard water). These divalent cations cause aggregation of the micelles, which then deposit as a dirty scum.
- 52. • These problems have been alleviated by the development of synthetic amphiphiles called detergents (or syndets). By using a much stronger acid for the polar head group, water solutions of the amphiphile are less sensitive to pH changes. Also the sulfonate functions used for virtually all anionic detergents confer greater solubility on micelles incorporating the alkaline earth cations found in hard water. Variations on the amphiphile theme have led to the development of other classes, such as the cationic and nonionic detergents. Cationic detergents often exhibit germicidal properties, and their ability to change surface pH has made them useful as fabric softeners and hair conditioners. These versatile chemical "tools" have dramatically transformed the household and personal care cleaning product markets over the past fifty years.
- 54. Thank You