Lipids 1.pdf

Lesson 6 Chapter 3 LIPIDS- STRUCTURE Learning Outcomes After this lesson, you should be able to: ▪ Understand the definition, and function of lipids ▪ Classify lipids ▪ Identify lipids Fatty acids and Essential fatty acids ▪ Classify lipids Fatty acids: Nomenclature of Fatty acids...

Lesson 6 Chapter 3 LIPIDS- STRUCTURE Learning Outcomes After this lesson, you should be able to: ▪ Understand the definition, and function of lipids ▪ Classify lipids ▪ Identify lipids Fatty acids and Essential fatty acids ▪ Classify lipids Fatty acids: Nomenclature of Fatty acids  Lipids Definition ▪ Named for the Greek word lipos, which means “fat.” ▪ Heterogenous group of biomolecules that contain fatty acids or a steroid nucleus. ▪ Steroids are a special type of fat molecules that have a unique structure. ▪ Water insoluble (hydrophobic). ▪ Soluble in organic and non-polar solvents as acetone, ether, chloroform and benzene. ▪ Extracted from cells using nonpolar organic solvents. ▪ Natural components of cell membranes, fat-soluble vitamins, and steroid hormones. Lipids, Continues Functions: ▪ Major source of energy for the body. ▪ Storage form of energy-triglycerides. ▪ Components of cell membrane. ▪ Some are hormones e.g. steroid hormone (cortisol, aldosterone, sex hormones) ▪ Some fat-soluble vitamins have regulatory or coenzyme function.  Biological Significance of Lipids 1. Lipids, or fats, are important in our diet because they provide a lot of energy. 2. In our bodies, fats are a great source of energy, and they are stored in a special tissue called adipose tissue. 3. Fats also act as insulation, keeping our bodies warm and protecting our organs. 4. Nervous tissue, which helps us feel and react to things, contains a lot of fats. In summary, lipids are important for energy, insulation, and the proper functioning of our bodies.  Biological Significance of Lipids 5. Lipids, in the form of lipoproteins, are important parts of cells and can be found in cell membranes, mitochondria, and cytoplasm. Lipoproteins are also crucial for transporting lipids in the blood. 6. Lipids are the source of fat-soluble vitamins, including vitamins A, D, E, and K. 7. They also provide essential fatty acids, which are important for our bodies.  Biological Significance of Lipids 8. Lipoproteins are responsible for the transfer of fats and vitamins in the blood. 9. Cholesterol has important role in the formation of hormones and vitamin D3, bile salts, sterols. 10. Prostaglandin generators have a role in influencing blood pressure and arteriosclerosis. 11. Have an important source to provide the body with the necessary fatty acids (linoleic acid - linolenic acid - Arachidonic). 12. Act as stimulants of some enzymes, in addition it act as electron transport components in the mitochondria.  Classes of lipids Simple lipids Conjugated Derived lipids (complex) lipids Esters of FA with alcohols Esters of FA with alcohols Obtained on hydrolysis of and additional group simple or complex lipids e.g. - Phospholipids( e.g. Triglycerides phosphatidic, ph cholin, -Fatty acids (Oil or fat) ph.Ethanolamin) - What are the differences -Cholesterol - Fat, Solid-saturated FA Glycolipids -Ketone bodies - Oil, Liquid unsaturated FA Sphingo--Lipoproteins. Waxes 9  Fatty Acids ▪ Obtained by the hydrolysis of neutral fats (triglycerides). ▪ Contain organic monocarboxylic acids with an aliphatic chain containing 4 to 24 carbon atoms. ▪ Are insoluble in water. ▪ The aliphatic chain may be saturated or unsaturated with one or more double bonds. Fatty acids: Metabolic fuel, building blocks for triglycerides, phospholipids and sphingolipids. Precursors for prostaglandins. 10 Fatty Acid Formulas The formulas for fatty acids are written as : condensed structural formulas. skeletal formulas. Insert structures of lauric acid (C12H24O2) both condensed structural formula and skeletal formulas 11  Nomenclature of Fatty Acids hydrocarbon with the same number of carbon atoms, the suffix –oic being substituted for the final –e in the name of the hydrocarbon. Butane-butanoic acid. ▪ The saturated fatty acid ends in –anoic, e.g. octanoic acid while the unsaturated fatty acid ends with the suffix –enoic acid, e.g. octadecenoic acid. ▪ The carbon atoms in the fatty acids are numbered from the –COOH group. ▪ The carbon atom adjacent to the –COOH is called as α-carbon atom. ▪ e.g: octadecenoic acid (oleic acid) is written as 18:1 ,9 i.e. the fatty acid having 18 carbon atoms with one double bond between carbon atom numbers 9 and 10. Oleic acid ▪ 1 10 9 18 ▪ CH3 – (CH2)7 – CH = CH – (CH2)7 - COOH  Two conventions for naming fatty acids Standard nomenclature (Part a) assigns the number 1 to the carboxyl carbon (C-1), and α to the carbon next to it. The position of any double bonds is indicated by ∆ followed by a superscript number indicating the lower-numbered carbon in the double bond. e.g: octadecenoic acid (oleic acid) is written as 18:9, i.e. the fatty acid having 18 carbon atoms with one double bond between carbon atom numbers 9 and 10. For polyunsaturated fatty acids, an alternate convention numbers the carbons in the opposite direction, assigning the number 1 to the methyl carbon at the other end of the chain (Part b).  FA classified according to the presence of double bond into: 1) Saturated Fatty Acids Saturated fatty acids have only single C—C bonds. molecules that fit closely together in a regular pattern. Strong attractions between fatty acid chains (have properties similar to alkanes). Solid at room temperature 14  Saturated Fatty Acids Containing even number of carbon atoms with the general formula of CnH2nO2. Fatty Acids Number of Formula Sources C-atoms *Acetic acid 2 CH3-COOH Carbohydrate fermentation Butyric acid 4 CH3-(CH2)2-COOH Butter Caproic acid 6 CH3-(CH2)4-COOH Butter and many fats of plant origin Caprylic acid 8 CH3-(CH2)6-COOH - Capric acid 10 CH3-(CH2)8-COOH - *Lauric acid 12 CH3-(CH2)10-COOH Coconut oil Myristic acid 14 CH3-(CH2)12-COOH - *Palmitic acid 16 CH3-(CH2)14-COOH Most fats of animal and plant origin *Stearic acid 18 CH3-(CH2)16-COOH - *Arachidic acid 20 CH3-(CH2)18-COOH Peanut oil Saturated Fatty Acids 16 2) Unsaturated Fatty Acids Unsaturated fatty acids have one or more double bond. naturally occurring have one or more cis double bond. cis and trans fatty acid. 17  Cis Fat Trans Fat Health Effect Generally good for health unless Detrimental — lowers good cholesterol and consumed in unreasonably high increases the level of bad cholesterol in the quantities. body. Harmful to heart health could cause cardiac death. Occurs Yes While some natural trans fats occur in meat naturally and dairy products, the majority of trans fats come from processed foods (i.e., hydrogenated oils). Arrangement of The chains of carbon atoms are on Hydrogen atoms are on the opposite side of the atoms the same side of the double bond, double bonds of the carbon chain, making the resulting in a bend. fat molecule straight. Melting Point Usually low. Some cis fats are liquid Usually high. Trans fats, like saturated fats, are at room temperature. solid at room temperature.  Unsaturated Fatty Acids ▪ According to the number of double bonds, they classified into: ▪ A)Those with one double bond are called as monounsaturated fatty acids. -These are present in nearly all the fats e.g. palmitic acid and oleic acid. CH3 – (CH2)5 – CH = CH – (CH2)7 – COOH ▪ B) Those with more than one double bond are called polyunsaturated fatty acids (PUFA): e.g. linoleic acid, linolenic acid and arachidonic acid. ▪ Cannot be synthesized in the body therefore are essential in nutrition and are also called essential fatty acids. ▪ These are found in vegetable oils e.g. cotton seed oil, corn oil. A) Monounsaturated Fatty Acids Unsaturated fatty acids with one double bond are called monounsaturated fatty acids. Insert table 17.1 monounsaturated fatty acids. 20 B) Polyunsaturated Fatty Acids Unsaturated fatty acids with more than one double bond are called polyunsaturated fatty acids. 21  Other Fatty acids ▪ Certain fatty acids have unique properties, such as hydroxy groups or cyclic structures. For example, ricinoleic acid in castor oil has a hydroxy group, while ricinoleic acid chaulmoogric acid in chaulmoogra oil has a heterocyclic ring. chaulmoogric acid ▪ These fatty acids have played a significant role in the treatment of leprosy.  Glycerol 1.Glycerol is a trihybrid alcohol because it has three hydroxyl groups. 2.Glycerol is often obtained as a by-product of the soap industry. 3.When dietary lipids undergo lipolysis, glycerol is released. 4.In the liver, glycerol can be converted into glucose  Sterols 1.Sterols and solid alcohols are steroids that have an alcoholic group. 2.They have a cyclopentanoperhydrophenanthrene nucleus, also known as the steroid nucleus or steroid ring. 3.Cholesterol is an important steroid found in the body, consisting of 27 carbon atoms, a hydroxyl group (-OH), a double bond, two methyl groups at C10 and C13, and a side chain at C17. 4.Cholesterol serves as a precursor for various compounds, including vitamin D3, bile acids and salts, as well as adrenocortical and sex hormones. 5.Cholesterol is widely distributed in all cells of the body, but nervous tissue is particularly rich in it  Cholesterol A steroid structure Cholesterol  Cholesterol ester Cholesterol esters: Structural component of membranes. steroid hormones, vitamin D and bile acids. O R-C=O  Prostaglandins [PG] Prostaglandins (PGs) are the compounds synthesized from arachidonic acid and other fatty acids having 20 carbon atoms. Arachidonic acid undergoes cyclisation at the center of the carbon chain forming a cyclopentane ring, known as Prostaglandins. All the naturally occurring PGs are called prostanoic acid.  Prostaglandins ▪ Six PGs of the E and F series are the primary PGs. ▪ All the PGs have an –OH group at C12 and trans double bond at C13. ▪ Prostaglandins are found in seminal fluid, plasma and other tissues. ▪ These have pharmacological and biochemical actions and act on smooth muscle, blood vessels and adipose tissues. Prostaglandins and Physiological Effects ▪ Prostaglandins have potent physiological effects. Some increase blood pressure. Some lower blood pressure. Some stimulate contractions and relaxation of smooth muscle in the uterus during the birth process and menstrual cycle. ▪ When tissues are injured, arachidonic acid in the blood is converted to PGE1 and PGF2 that produce inflammation and pain in the area. NSAIDs and Prostaglandins Several nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, block production of prostaglandins decreasing pain, inflammation, and fever. 31  Omega-3 and Omega-6 Fatty Acids Fish and vegetable oils have high levels of unsaturated fats. ▪ In vegetable oils, they are mostly omega-6 with the first at C6. Linoleic acid ▪ In fish oils, they are mostly omega-3 with the first at C3. CH3─CH2─(CH═CH─CH2)3─(CH2)6─COOH 1 3 32 Linolenic acid Omega-6 and Omega-3 Fatty Acids 33 Omega-3 Fatty Acids Important of Omega-3 fatty acids: lower the tendency of blood platelets to stick together, thereby reducing the possibility of blood clots. Can help to reduce risk of heart disease. They are found in salmon, tuna, and herring. 34 Biological Significance of Essential Fatty Acids ▪ Cholesterol helps in its transport and metabolism. ▪ Besides, arachidonic acid is also a precursor of prostaglandins. ▪ Essential fatty acids are also the constituents of the cell membrane and membrane of the mitochondria. ▪ These are essential for normal growth and health.