Lipid Chemistry and Metabolism PDF

BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les INTRODUCTION TO LIPIDS 5. STRUCTURAL LIPIDS  Best exempl...

BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les INTRODUCTION TO LIPIDS 5. STRUCTURAL LIPIDS  Best exemplified by phospholipids which are the main  Comprise of very heterogeneous group of compounds constituent of the cell membrane o No common unifying element in terms of structure  Sphingomyelin and sphingosine are important o Related more by physical rather than chemical membrane components properties  2 Common characteristics of lipids: FATTY ACIDS 1. Low solubility in water 2. High solubility in organic non-polar solvents - Examples of organic solvents are benzene, chloroform and ether  Largely hydrophobic  Made up of hydrocarbon molecules CLASSIFICATION OF LIPIDS Lipids can be classified based on the following: 1. Structure  Components are: o Carboxylic acid functional group (COOH) a. Simple lipids- made up of few elements and can no longer o Long hydrocarbon chains be broken down into smaller units  Fatty acids are naturally occurring carboxylic acids attached to an i. Fats and oils: these are esters of fatty acids unbranched hydrocarbon with glycerol  Fatty acids can be classified by: ii. Waxes: esters of fatty acids with high 1. Length of the hydrocarbon tail molecular weight monohydric alcohols 2. Degree of unsaturation b. Complex lipids- these are biological molecule o Position of double bond in the chain (if components. These are esters of fatty acids and alcohols unsaturated) together with some other head groups i. Phospholipids: esters of the above type Types of Fatty Acids containing phosphoric acid residue Long chain  12-16 carbon a) Glycerophospholipids: alcohol is Medium chain  6-10 carbons glycerol Short chain  < 6 carbons b) Sphingophospholipids: alcohol is sphingosine  Whether fatty acids are long, medium or short chains, they can be ii. Sphingolipids further divided into two: saturated and unsaturated iii. Glycolipids: lipids containing fatty acid, sphingosine and carbohydrate residues SATURATED FATTY ACIDS c. Precursor and derivatives of lipids such as glycerol, steroids, fatty aldehydes, ketone bodies, hormones, Vitamin D 2. Ability to undergo hydrolysis under alkaline condition PALMITIC ACID a. Saponifiable- exposure to alkaline media will break them down into simpler components b. Nonsaponifiable- lipids can no longer undergo hydrolyzation in an alkaline condition Palmitic acid is the prototype for a long chain saturated fatty FUNCTIONS OF LIPIDS acid. It contains 16 carbons 1. FUEL  Saturated fatty acids does not have any double bond  Fat is the most concentrated storage form of energy  Carbon chains are filled with hydrogen (H) atoms  Yields 9 cal/g  They have a straight chain which means that its molecules are 2. SERVE AS THERMAL INSULATORS close to each other  Fat is a poor conductor of heat which provides excellent  They tend to compact as a molecule heat insulation  Appear solid at room temperature 3. PROVIDES PROTECTION  They have a higher melting point  Fat provides padding to protect internal organs  They have a very ordered structure  Vital organs are covered with a lot of adipose tissue thus  Found in animal sources like as butter, lard, and some tropical providing mechanical protection plants like palm and coconut 4. BUILDING BLOCKS OR PRECURSORS  Fat can serve as a building block or precursor to other biologically active materials (e.g. hormones, vitamins, second messengers) 1 BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les UNSATURATED FATTY ACIDS Picture on the lower left: Oleic Acid and Linoleic Acid Both fatty acids contain 18 carbons, the difference is that the first fatty acid (Oleic Acid) is a monounsaturated FA meaning it contains only one double OLEIC ACID bond. Whereas the second fatty acid (Linoleic Acid) is a polyunsaturated FA because it contains two double bond. Between these two fatty acids, Linoleic Acid has a lower melting point due to having more double bond. Unsaturated fatty acid, like oleic and linoleic acid, can be converted into a saturated fatty acid through a reaction called Hydrogenation Oleic Acid is the prototype for long a long chain unsaturated fatty acid. It has 18 carbons and at the very center, you’ll find the presence of a double bond Picture showing  Unsaturated fatty acids has at least one double bond or more the process of  Due to the presence of double bond (C=C) it appears HYDROGENATION “crooked” meaning they have curves  Those curves are the result of double bond called “kinks”  “Kinks” are bends in the hydrocarbon chain  They are less compact  At room temperature unsaturated fatty acids are usually liquids  They have a lower melting point Why do we want to hydrogenate an unsaturated fatty acid?  They have a less ordered structure Answer: The reason for this is that saturated fatty acid is more stable than unsaturated fatty acids, and being more stable means having a longer shelf  Can be further divided into: monounsaturated or life. So hydrogenating an unsaturated fatty acids prolongs the shelf life of polyunsaturated foods. Through hydrogenation, it will make the oil of the food solid at room  Monounsaturated = 1 C=C temperature.  Polyunsaturated= 2 or more C=C Why not just use butter for processed food, since it contains saturated fatty RECAP acids? SATURATED FATTY ACIDS Answer: Butter is more expensive, so a cheaper way to prolong the shelf life Saturated fatty acids have a carbon chain that are filled of the food is to simply hydrogenate it. with hydrogen. They have no presence of double bond in the chain How do we hydrogenate an unsaturated fatty acid? This is kind of fatty acid is usually found in animal sources It should be done at a high temperature in the presence of hydrogen like as butter, lard, and some tropical plants like palm and and a catalyst (e.g. nickel) coconut So heating unsaturated fatty acid at very high temperature will Saturated fatty acids have molecules that are closer to definitely yield hydrogenated saturated fatty acid each other so they are expected to be solid at room But we have to take note that it is not only hydrogenated fatty acid temperature and they have a higher melting point that we obtain under these conditions, we also obtain other undesirable side products which include “trans fatty acids” UNSATURATED FATTY ACIDS Trans fatty acids have a double bond that is moved to a different Unsaturated fatty acids it lacks some hydrogen so it is position expected to at least have a double bond. So most of the products will include a saturated fatty acid It can be further divided into two: monounsaturated and (hydrogenated) and some amount of trans fatty acids polyunsaturated Trans fatty acids have a simple rearrangement of the configuration of Monounsaturated fatty acid has only one double bond the hydrogen in the double bond resulting to a trans configuration Polyunsaturated fatty acid has two or more double bond Trans fatty acids are undesirable because it is associated with health The presence of more double bond results to more “kinks” risks So the more double bond there are, the kinkier the fatty acid is Unsaturated fatty acids continued…… 2  BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les RECAP Picture on the lower left: Hydrogenation is simply the addition of hydrogen to an unsaturated fatty acid carried out under very high temperature All these fatty acids have the same number of carbons but they differ in Complete hydrogenation is what we want wherein the hydrogen will configuration. Stearic acid is a saturated fatty acid, it has a straight chain. attack the double bond resulting to the formation of the saturated Oleic acid has one double bond, while Linoleic acid has two (2) double bond fatty acid and Linolenic acid has three (3) double bond. These are unsaturated fatty However, we also expect the formation of some undesirable side acids due to the presence of double bond and these create “kinks” in the products and it includes the trans fatty acids which is associated with structure. several health risks such as elevation of LDL (bad cholesterol) and lowering of HDL (good cholesterol). Such elevation of LDL and Exercise: lowering of HDL puts a person at risk of development of Which of the three fatty acids have the lowest melting point? Linolenic acid atherosclerosis, heart disease, diabetes mellitus and some form of Which has the highest melting point? Stearic acid cancer NOMENCLATURE OF FATTY ACIDS 2 CONFIGURATIONS OF UNSATURATED FATTY ACIDS Systematic Basis for Naming Fatty Acids  Generally, fatty acids can be named base on the number of hydrocarbons (C) and presence or absence of a double bond (C=C) Saturated Fatty Acids:  Named based on the number of hydrocarbons (C) present  For Saturated fatty acid: Parent hydrocarbon + oic Example: Stearic acid- has 18 carbons: octadeca (means 18) + oic = octadecanoic acid Unsaturated Fatty Acids:  For Unsaturated fatty acid, the principle is still the same which is based on the number of hydrocarbons (C) but now we consider the number of double bond  The H atoms are on the same side of the bond # of Double Bond Suffix CIS configuration  Has a kink on the 1 Enoic acid hydrocarbon chain 2 Dienoic acid  Bent in 120o at the C=C 3 Trienoic acid  The H atoms are on the opposite sides of the bond Example: TRANS configuration  Still linear Oleic acid- has 18 carbons: octadeca (means 18) + enoic =  Behaves much like a octadecenoic acid saturated fatty acid Linoleic acid- has 18 carbons: octadeca (means 18) + dienoic = octadecadienoic acid Other Examples of Fatty Acids: Linolenic acid- has 18 carbons: octadeca (means 18) + trienoic = octadecatrienoic acid  For Unsaturated fatty acid: Parent hydrocarbon + suffix of # of double bond Common names for fatty acids such as Palmitic acid are based on where they came from. Palmitic acid came from palm oil. FATTY ACID NUMBERING There are two methods for numbering fatty acids: delta (Δ) numbering system and omega (ω) numbering system  The difference between the two system is the reference point or where they start the counting (where they start the C1)  Adjacent carbons are known as α,β,ϒ carbons respectively (C2, C3, C4) Delta (Δ) Numbering System  Starts with the carboxyl group (COOH) or delta end  Delta (Δ) end’s hydrocarbon will be read is C1 3  BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les Omega (ω) Numbering System Linoleic Acid  Starts with the methyl end (H3C or CH3) or omega end  ω6  Omega (ω) end’s hydrocarbon is will be read as C1  Found in meats & poultry  Fat oils, nut seeds  Vegetable oils (corn, sunflower, soybean) Linolenic Acid  ω3 Example: Oleic Acid  Found in fish & oyster (tuna, mackerel, sardines, salmon) – at least twice a week serving  Anti-inflammatory  Prevent heart disease, arthritis, cancer  ADA and DHA- form Omega-3 DELTA SYSTEM: 18: Δ1-9 Where, 18 = number of hydrocarbon (C) atoms in the molecule Δ = number of double bond (C=C) – position of double bond (C=C) OMEGA SYSTEM: ω-9 Where, ω = position of double bond (C=C) Example: Linoleic Acid DELTA SYSTEM: 18: Δ2-9,12 OMEGA SYSTEM: ω-6,9 HELPFUL VS. BAD FATTY ACIDS Note: If there are more than one double bond, we add a comma and then PROSTAGLANDINS write the number where the double bond is located  Form of fatty acid that is physiologically very useful  A 24-carbon fatty acid Remember where DELTA and OMEGA starts the number reading of C  Important class of local hormone which regulates the immune system  Involved in the contraction of smooth muscles, control of inflammation, body temperature, and other physiologic processes  Mediators for inflammation and pain  Important biomolecules and are derivatives of unsaturated fatty acid (ω6)  Derived from arachidonic acid which is polyunsaturated fatty acid ESSENTIAL FATTY ACIDS with 4 double bonds  Linoleic Acid and Linolenic Acid are both essential fatty acids  Arachidonic acid is acted upon by enzyme COX (Cyclooxygenase) and  Essential fatty acid means that the body does not produce or will be synthesized into Prostaglandin synthesize them and that it should be provided in the diet  Play a role in normal growth and development  Prevents diseases like cancer, hypertension & heart diseases 4 BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE Lipid Chemistry and Metabolism Doc Les TRIACYLGLYCEROL 2. Saponification Number- amount in mg of KOH or NaOH required to completely saponify 100g of oil/fat  Liberate KOH or NaOH in saponification, forming soap In Saponification Number, you are completely saponifying the oil  Storage form of fatty acids or fats. Not only you are neutralizing the fatty acids, but you are  Commonly called as fats and oils also neutralizing the fatty acids that are bound to glycerol, completely saponifying it. This is carried out in the presence of  Fatty acid esters of glycerol KOH or NaOH, the glycerol is liberated and the fatty acids are o The backbone is glycerol and esterified to it are 3 fatty acids neutralized producing the sodium or potassium salt (soap) of the  What makes fat different from oil? fatty acid. o Fat are usually solid in room temperature and are of animal source 3. Iodine Number- g of iodine that combine with 100g of oil/fat o Oil are liquid in room temperature and are usually of plant  Indicate degree of unsaturation of fat/oil origin  Higher iodine number, higher degree of unsaturation,  Synthesized through dehydration reaction between glycerol and more double bond (C=C) fatty acids  You can reverse the reaction through saponification. In the presence of sodium or potassium hydroxide and heat, you reverse the process, breaking down the bonds releasing the fatty acids and glycerol  Can be saturated or unsaturated  When it is saturated it is expected to have a straight chain, more ordered and more compact in structure, they appear solid at room temp, and requires high temperature to melt them  When it is unsaturated there’s a presence of double bond, there’s a HEALTH EFFECTS OF DIETARY FAT presence of kink in the hydrocarbon chain, less compact, less  Excess fat intake ordered, appears liquid at room temperature, and requires lower o Obesity temperature to melt them o Diabetes o Caner (Colon & Breast) CHEMICAL CHARACTERIZATIONS OF FATS o Heart Disease 1. Acid Number- amount in mg of KOH or NaOH required to neutralize  Raise blood cholesterol free fatty acids in 1g of oil/fat  High fat in diet = high calorie diet  More amount of KOH or NaOH needed, more free fatty  Promote breast cancer and colonic cancer acid  To prevent its negative effects, limit to