Lipid's Structure and Function PDF

Lipid’s Structure and Function By Dr. Marwa Mohammed Hosny Associate professor of Medical Biochemistry & molecular biology Lecture outlines Definition of Lipids Classification of Lipids:- Simple lipids Compound lipids Derived lipids Function of lipids Definition of L...

Lipid’s Structure and Function By Dr. Marwa Mohammed Hosny Associate professor of Medical Biochemistry & molecular biology Lecture outlines Definition of Lipids Classification of Lipids:- Simple lipids Compound lipids Derived lipids Function of lipids Definition of Lipids: Organic compounds that are insoluble in aqueous solution and soluble in organic solvents (ether, chloroform, benzene, acetone). Classification of Lipids:- Simple lipids Compound lipids Derived lipids Table 1 : Saturated fatty acids 3-Nervonic acid (Unsaturated lignoceric acid). It is found in cerebrosides. It is Ꙍ9, C24:115, i.e., has 24 carbons and one double bond located at carbon number 15 and involving carbon 16. CH3 – (CH2)7 CH= CH – (CH2)13- COOH 2- Alpha-Linolenic acid: Table 2 : Unsaturated fatty acids Fatty acids are classified according to several bases as follows: I. According to presence or absence of double bonds they are classified into: A-Saturated Fatty Acids B-Unsaturated Fatty Acids II. According to nutritional importance into: A-Essential Fatty Acids B-Non-essential Fatty Acids II. According to nutritional importance into: A-Essential Fatty Acids They can not be synthesized in the human body and must be taken in adequate amounts in the diet. They are precursor of other F.A. by chain elongation & desaturation. B-Non-essential Fatty Acids They can be synthesized in the human body. Triacylglycerol consist of two parts 1. Glycerol 2. Three Fatty Acids 2-Bee wax: myricyl alcohol (30C)+ palmitic acid (16C fatty acid) Myricyl alcohol is a fatty alcohol of the general formula CH3(CH2)28COOH also known as melissyl alcohol or Triacontanol. (II) Conjugated Lipids (Compound lipids): 1- Phospholipids 2- Glycolipids 3- Lipoproteins (II) Conjugated Lipids (Compound lipids): 1- Phospholipids Base 1-Phospholipids Definition: Phospholipids are compound lipids, which contain phosphoric acid group in their structure. Structure: phospholipids are composed of: 1. Fatty acids (a saturated and an unsaturated fatty acid). 2. Nitrogenous base (choline, serine, threonine, or ethanolamine). 3. Phosphoric acid. 4. Fatty alcohols (glycerol or sphingosine). A. Glycerophospholipids Structure of some glycerophospholipids  B. Sphingophospholipids They contain sphingosine as the alcohol instead of glycerol. Sphingosine: - It is the alcohol present in sphingolipids. - It is synthesized in the body from serine and palmitic acid. Example of Sphingophospholipids : Sphingomyelins Sphingomyelins are found in large amounts in brain and nerve tissue.  What are Phospholipids? Lipids containing phosphorus Are good emulsifying agents Found in cell membranes and in subcellular structures (lipid & water interaction)  3-Derived Lipids Derived Lipids Substances derived from simple & compound by hydrolysis. Examples Fatty acids Derived Lipids Alcohols: -Glycerol -Sphingosine -Mericyl alcohol -Sterols: Cholesterol Glycerides Steroids Fat soluble vitamins (A,K,E & D) 41 Cholestorol (membrane sterol)  Eicosanoids Overview  Eicosanoids are a powerful hormone like molecules with potent effects on virtually every tissue in the body  these agents are derived from metabolism of 20-carbon, polyunsaturated fatty acids (eicosanoic acids).  Eicosanoids – The Eicosanoids include: 1. The prostaglandins 2. Leukotrienes 3. Thromboxanes 4. Hydro-peroxy-eicosa-tetraenoic Acids (HPETEs) 5. Hydroxy-eicosa-tetraenoic Acids (HETEs).  Biosynthesis – Arachidonic acid, the most common precursor of the eicosanoids, is formed by two pathways: 1. Phospholipase A2-mediated production from membrane phospholipids; this pathway is inhibited by glucocorticoids. 2. Phospholipase C.  Effects of Eicosanoids Induction of inflammation Mediation of pain signals Induction of fever Smooth muscle contraction (including uterus) Smooth muscle relaxation Protection of stomach lining Stimulation of platelet aggregation Inhibition of platelet aggregation Sodium and water retention Chemical composition of lipids Importance of lipids  Lipoprotein & Acts as fuel in Insulating effect Phospholipids (cell wall & mitochondrion the body constituents) Padding & protection of internal organs Vitamin A,D,E,K fat soluble Building vitamins Materials (hormones) Supply essential Nervous fatty acids system: Rich in lipids 50