L11 Lipids-II Lecture Notes PDF
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Uploaded by CongratulatoryEllipsis4870
Gulf Medical University
2024
Dr. Salah Eldin Omar
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Summary
These lecture notes detail the chemistry of TAG and phospholipids, focusing on properties, reactions, and functions. The document includes learning objectives along with key details on simple and complex lipids, including glycolipids and sphingomyelins. This material is likely for an undergraduate level chemistry or biology course.
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L11 Lipids-II CHEMISTRY OF TAG AND PHOSPHOLIPIDS Dr. Salah Eldin Omar December 10, 2024 www.gmu.ac.ae College of Health Learning objectives 1. Describe the properties and reactions of...
L11 Lipids-II CHEMISTRY OF TAG AND PHOSPHOLIPIDS Dr. Salah Eldin Omar December 10, 2024 www.gmu.ac.ae College of Health Learning objectives 1. Describe the properties and reactions of Triacylglycerol. 2. List the main functions of glycolipids and phospholipids in the body 3. Name the main eicosanoid derivatives and their functions A- Simple lipids Fatty acid + Alcohol Eg. TAG TRIACYLGLYCEROL (NEUTRAL LIPIDS) Triacylglycerides are composed of a glycerol (shown in blue) backbone to which 3 fatty acids (shown in red) are esterified. Triacylglycerides TAG’s are the storage form of lipids in adipose tissue. TAG’s are insoluble in water (hydrophobic) and are non polar. TAG’s are not the structural components of biological membranes Physical properties of triglycerides depend on their fatty acid components TAG’s containing higher proportions of unsaturated FA’s short and medium chain FA are liquid at 200C. They are called as oils and are present in vegetables. TAG’s containing mainly saturated long chain FA’s are solid at ordinary temperature. They are called as fats. Fats are mainly of animal origin. PROPERTIES OF TRIACYLGLYCEROLS 1. HYDROLYSIS TAG’s are hydrolyzed to glycerol and 3 molecules of FA’s. Lipase Lipase Lipase TAG DAG MAG GLYCEROL Hydrolysis of triglycerides in the body occurs during digestion of dietary fat and breakdown of TAG in the adipose tissue. 2) SAPONIFICATION The hydrolysis of TAG by alkali to produce glycerol and soap is known as saponification. TAG + 3 NaOH Glycerol + 3 R-COONa O (SOAPS) O CH2 O-CR saponification + 3NaOH RCO- CH O CH2 OH O CH2 O-CR - + A triacylglycerol CHOH + 3 RCO Na (a triglyceride) Sodium soaps CH2 OH 1,2,3-Propanetriol (Glycerol; Glycerin) 3) ADDITION REACTIONS Addition of hydrogen / halogen to double bond of FA. Hydrogenation of oil leads to solidification and saturation. --CH = CH -- + 2 H --CH2 - CH2— 4) RANCIDITY Rancidity is the term used to represent the deterioration of fats and oils resulting in an unpleasant taste and smell. Fats containing unsaturated FA’s are more susceptible to rancidity. Rancidity occurs when fats and oils are exposed to air, moisture, light, bacteria etc. Antioxidants are the substances which can prevent the occurrence of oxidative rancidity. B. COMPOUND OR COMPLEX LIPIDS Fatty Acid + Alcohol + Some other Molecules It includes : I. Phospholipids II. Glycolipids III. Sulpholipids All these are amphipathic as they contain both hydrophobic and hydrophilic regions in the same molecule. They are important structural and functional components of the bio membranes.. B- COMPOUND OR COMPLEX LIPIDS 1- LECITHIN (Phosphatidyl Choline) Fatty acid attached to the β-carbon is a PUFA molecule. These are the most Fatty Acid + Glycerol + abundant group of Phosphoric acid + Choline phospholipids in the cell membrane. 2- Dipalmitoyllecithin (Lung surfactant) Present in large amounts in the extracellular liquid layer that lines the alveoli of normal lungs. Constant supply is necessary for the normal lung function. 3- SPHINGOMYELINS Ceramide + Phosphorylcholine. Sphingomyelins are the only sphingolipid that contain phosphate and have no sugar. Important structural components of nerve cell membranes (myelin sheath). It is also important in biological fluids like bile, amniotic fluid. 4- Glycolipids are widely distributed in every tissue of the body particularly in nervous tissue. They occur in the outer leaflet of plasma membrane where they contribute to cell surface carbohydrates and are important: - ABO & blood group substances.