AIU Lecture Notes on Lipids (Week 4) PDF

AIU-PT Prof. Rasha Nassra Medical Biochemistry & Molecular Biology SUBJECTS Water TO BE COVERED Macromolecules Enzymology Vitamins & Minerals Cell Membrane & Signal Transduction Molecular Biology SUBJECTS...

AIU-PT Prof. Rasha Nassra Medical Biochemistry & Molecular Biology SUBJECTS Water TO BE COVERED Macromolecules Enzymology Vitamins & Minerals Cell Membrane & Signal Transduction Molecular Biology SUBJECTS TO BE COVERED LIPIDS Students’ learning outcomes Define lipids Classify lipids Define fatty acid Describe structure of fatty acid Identify different classification of fatty acids Identify clinical significance of each classification of fatty acids State dietary sources of essential fatty acids  What Are Lipids ? Heterogeneous group of organic compounds contain C , H , and O may also contain P, N, and S related, either actually or potentially to fatty acids  What Are Lipids ? Relatively water-insoluble (hydrophobic) Highly soluble in non-polar (organic) solvents as benzene, chloroform and ether  What is the function of lipids? Important dietary constituents, because of their high energy value (provide more energy per gram than carbohydrates and proteins.) Storage form of energy (triglycerides) Serve as a thermal insulator in the subcutaneous tissues and around organs Enter in the structure of Cell membrane Provide the body with its need of Fat-soluble vitamins (A,D,E,K)  What is the function of lipids? Act as electric insulators in neurons Metabolic regulators (steroid hormones and prostaglandins) Lipoprotein  Classification of lipids Derived Simple Compound lipid lipid lipid  CLASSIFICATION OF LIPIDS I. SIMPLE LIPIDS: 1.True fats: Esters of fatty acids with glycerol. 2. Waxes: Esters of fatty acids with higher molecular weight monohydric alcohol II. COMPLEX LIPIDS (COMPOUND LIPIDS): Esters of fatty acids with alcohol and in addition they contain another group 1. Phospholipids: These lipids contain fatty acid, alcohol, the additional group phosphoric acid 2. Glycolipids These lipids contain fatty acid, alcohol, the additional group carbohydrate 3. Lipoproteins lipids and proteins.  III. DERIVED LIPIDS: Derived from hydrolysis of simple and compound lipids 1. Fatty acids. 2. Glycerol. 3. Alcohols (other than glycerol) Or related potentially to fatty acid 1. Steroids 2. Carotenoids 3. Fat soluble vitamins: Vitamins A, D, E and K.  *** Clinical Applications ✓ 1. Excessive fat deposits cause obesity. Truncal obesity is a risk factor for heart attack. ✓ 2. Abnormality in cholesterol and lipoprotein metabolism leads to atherosclerosis and cardiovascular diseases. ✓ 3. In diabetes mellitus, the metabolisms of fatty acids and lipoproteins are deranged, leading to ketosis.  FATTY ACIDS Definition Aliphatic monocarboxylic organic acids. They are obtained mostly from the hydrolysis of simple lipids  Acid means proton donor Aliphatic means no ring structure Organic means the active group donating the proton is the carboxylic group Monocarboxylic means possess only one carboxylic group Structure of fatty acids CH3 CH3-CH2-CH2---------- It consists of a hydophobic hydrocarbon chain with terminal carboxyl group (COOH)(hydrophilic) and one (CH3) group in the other terminus Hydrophilic part Hydrophobic part (carboxyl group) (hydrocarbon chain)  There are methods of numbering of fatty acid carbons CH3– CH2 – CH2 - CH2 – CH2 – COOH 1. Δ-numbring 6 5 4 3 2 1 2. Greek (ξ) () () () () 3.  numbering (1 ) (2 ) (3) (4) (5) Most of fatty acids present in nature contain an even number of carbon atoms  Classification of Lipids According to Saturation Chain Biological length **Cis/Trans  Classification of F.A 1-According to chain length of F.A: Short (Low)12 carbons CLINICAL SIGNIFICANCE Short chain fatty acids can be absorbed without aid of bile salts (less hydrophobic) Longer chain fatty acids require aid of bile salts for their absorption( more hydrophobic) Low fatty acids (short chain fatty acids): Containing 10 carbon atoms or less (from 2-10). Such as: Acetic acid (2 C): CH3-COOH Butyric (4 C): CH3-CH2-CH2-COOH Caproic (6 C): CH3-(CH2)4-COOH High fatty acids (Long chain fatty acids): Contain more than 10 carbon atoms. Palmitic (16 C): CH3-(CH2)14-COOH Stearic (18 C): CH3-(CH2)16-COOH Lignoceric (24 C): CH3-(CH2)22-COOH. Let’s apply!  CASE Scenario A 35 year old woman suffering from colics and pain following ingestion of high fatty meal imaging study revealed inflammation of her gall bladder which type of fatty food would you advise her to eat ? 1- Lipid with unsaturated fatty acid 2- Lipid with short chain fatty acid 3- Lipid with long chain fatty acid 4- Lipid with saturated fatty acid  2-According to Saturation of fatty acids saturated or unsaturated (the presence of double bound called unsaturated) A-Saturated FA(No Double bond) General formula: CH3 - (CH2)n - COOH n represent number of methylene (CH2) groups e.g palmitic acids (16 Carbons) CH3 - (CH2)14 - COOH stearic acid (18 Carbons) CH3 - (CH2)16 - COOH  B-Unsaturated FA ( presence of double bound) 1-Monounsaturated Oleic acid 18 C (1 double bound) 2-Polyunsaturated Linoleic 18 C (2 double bound) Linolenic 18 C (3 double bound) Arachidonic (4 double bound) Unsaturated fatty acids: contain one or more double bonds. Classified into: a.Monounsaturated fatty acids (monoenoic) contain one double bond. Oleic acid ω 9 18: 1; 9. CH3-(CH2)7-HC = CH-(CH2)7-COOH b.Polyunsaturated fatty acids: (Polyenoic) Contain more than one double bond Linoleic 18: 2; 9, 12: (ω 6). CH3-(CH2)4-CH = CH-CH2-CH = CH-(CH2)7-COOH Linolenic 18: 3; 9 12, 15: ( ω 3). Trienoic acid CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH = CH(CH2)7-COOH Arachidonic 20: 4; 5, 8, 11, 14: (ω 6). CH3-(CH2)3-(CH2-CH = CH)4 – (CH2)3-COOH  Saturated (no double bond) Unsaturated (presence of one or more double bonds) CLINICAL SIGNIFICANCE Saturated fatty acids are densely packed (little space between molecules ) so are in a solid state Unsaturated fatty acid are kinked around axis of double bond not densely packed so are in liquid state  Stearic acid (18 Carbons) 18 C Oleic acid 18 C (1 double bound  9) Lipids surrounding internal organs as the heart and kidneys to protect them and maintain their position are made of 1- Saturated fatty acid 2- Polyunsaturated fatty acids 3- Monounsaturated fatty acids 4-Short chain fatty acids  3) Biological classification A) Essential Fatty acids Can’t be synthesized inside the body They are polyunsaturated fatty acids linoleic acid, Linolenic acid,. B) Relatively essential fatty acid : Arachidonic acid (From Linoleic) C) Non essential fatty acid Can be synthesized inside the body  ESSENTIAL FATTY ACID Relatively essential http://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Arachidonic_acid_structure.svg/620px-Arachidonic_acid_structure.svg.png Arachidonic acid (20 C)  6  Sources of linoleic acid (w6) ▪ Safflower oil ▪ Sunflower oil ▪ Peanut butter ▪ Corn oil ▪ Soybean oil ▪ sesame Eating too much linoleic acid disrupts healthy cellular function and contributes to inflammation  Sources of linolenic acid ( ω 3) ▪ Walnuts ▪ Flaxseed oil ▪ Chia seeds ▪ Soybean oil ▪ Salmon ▪ Sardines ▪ Tuna  Functions Essential FAs: Growth and development They are used for synthesis of inflammatory mediators eicosanoic acids (These compounds, derived from eicosa (20-carbon) polyenoic fatty acids) which are the precursors of Prostaglandins Membrane formation & function Plasma cholesterol lowering.  Deficiency of essential fatty acids In infants with low fat diet & IV nutrition with low essential FA) leading to: Dermatitis+ poor wound healing+ impaired lipid transport  The trans fat in the foods we eat is formed through a manufacturing process that adds hydrogen to vegetable oil, which converts the liquid into a solid fat at room temperature. This process is called hydrogenation  Naturally occurring unsaturated long chain fatty acids are all of the cis- configuration. Trans fatty most of them arise as a byproduct of saturation of fatty acids in the process of hydrogenation CH3 CH3 (hardening) of naturally occurring oils (during the manufacture of margarine). Oleic acid Elaidic acid H H Trans form Cis form H H COOH COOH The greatest danger from Trans fat lies in its capacity to distort the cell membranes. The primary health risk identified for trans fat consumption is an elevated risk of coronary heart disease. Trans fats have an adverse effect on the brain and nervous system. Trans fat from the diet is incorporated into brain cell membranes and alter the ability of neurons to communicate