Lipid Chemistry II Lecture 3 (Oct 24, 2024) - Biochemistry 1 PDF

Course Title : Biochemistry I Course Code : FM104 Department : Biochemistry Lecture Title: Lipid chemistry II Lecturer Name: Ass. Prof. Dr. Omnia Safwat El-Deeb Lecture Objectives: Each student at this lecture should be able to: Define TAG and Know their prope...

Course Title : Biochemistry I Course Code : FM104 Department : Biochemistry Lecture Title: Lipid chemistry II Lecturer Name: Ass. Prof. Dr. Omnia Safwat El-Deeb Lecture Objectives: Each student at this lecture should be able to: Define TAG and Know their properties Identify different types of phospholipids Recognize biomedical importance of phospholipids Know Types & Functions of lipoproteins Know structure & functions of cholesterol Contents: TAG and their properties Different types of phospholipids Biomedical importance of phospholipids Types & Functions of lipoproteins Structure and functions of cholesterol  Triacylglycerol (TAG) (Neutral fats) Main storage form of lipids in the body. Stored in the adipose tissues. Structure of triacylglycerol (glycerol + fatty acids) Glycerol Glycerol is a tri-hydroxy alcohol (colorless, odorless, viscous liquid with sweet-tasting and non-toxic). It is synthesized in the body from glucose  Formation of TAG Triacylglyceride is formed from Glycerol and three Fatty acids.  Physical Properties of Triacylglycerol 1. They are insoluble in water (hydrophobic) but soluble in fat solvents (ether, benzene) 2. Neutral lipids may be oils or fats. 3- They are hydrolyzed (digested) by pancreatic lipase enzyme into glycerol and free fatty acids. 4.Saponification is a process by which triglycerides are reacted with sodium or potassium hydroxide to produce glycerol and a fatty acid salt called "soap  5. Additions of halogens to oils: O Oils can take halogens (iodine) at the positions of double bonds. O Iodine number is the number of grams of iodine absorbed by 100 g of fat or oil and is used to assess the degree of unsaturation of fat. It is directly proportional to the degree of unsaturation of fatty acid. 6. Hydrogenation of oils: When vegetable oils are hydrogenated by addition of hydrogen they produce the corresponding artificial fats (margarine) as they become fully saturated. 7- O Effects of rancid fats: Products of rancidity are toxic. Products of rancidity destroy other factors of food, e.g. fat-soluble vitamins & essential FA O How to protect fat from rancidity? Keep the food in cold place to inhibit the action of bacterial lipase. Replace the O2 by inert gas like N2. Put the food in vacuum. Add antioxidants as vitamin E & C.  II. Compound Lipids O Compound lipids contain lipid part and non-lipid part. They include: 1- Phospholipids 2- Glycolipids 3- Lipoproteins 1. Phospholipids Definition: Compound amphipathic lipids composed of fatty acid, alcohol, phosphoric acid and alcohol Types: Based on the alcohol present, phospholipids are classified into. O A. Glycerophospholipids: Their alcohol is glycerol O B. Sphingophospholipids: Their alcohol is sphingosine. Glycerophospholipids: - 2 Fatty acids - Phosphate - Base + GLYCEROL Sphingophospholipids: - 1 Fatty acid - Phosphate - Choline + SPHINGOSINE  A-Glycerol-phospholipid 1) Phosphatidic Acid O Definition: Simplest phospholipid. Itdoes not contain any nitrogenous base. O Structure: Glycerol + 2 Fattyacid + Phosphate group  2)Lecithin (Phosphatidylcholine) Structure: Phosphatidicacid + Choline. O Importance: O Dipalmitoyl Lecithin is a major constituent of lung surfactant. O Insufficient surfactant production in preterm infant leads to respiratory distress syndrome (RDS), which is common causeof neonatal morbidity 3) Cephalin (Phosphatidyl ethanolamine): -Structure: Phosphatidicacid + Ethanolamine. - Importance: Component of Cell membrane Playa role in blood coagulation. O 4) Phosphatidyl serine - Structure: Phosphatidicacid + serine. - Importance: Plays an important role in Programmed cell death O 5) Phosphatidyl inositol O Structure: Phosphatidicacid + Inositol (six membered cyclic alcohol) O Importance: O Play a major role as a second messenger during signal transduction forcertain hormones. 6- Cardiolipin: First isolated from cardiac muscle and hence the name O Structure: O Two molecules of phosphatidic acid + a moleculeof Glycerol, i.e. Diphosphatidyl glycerol O Importance: It is a major lipid of the inner MM Decreased cardiolipin level or alteration in its structure or metabolism cause mitochondrial dysfunction 2. Glycolipids - Definition: Complex lipids which contain carbohydrates, but no phosphoric acid. - Widely distributed in all tissues ( in nervous tissue and brain) - Types of Glycolipids: 1. Cerebrosides 2. Globosides 3. Gangliosides  3-Lipoproteins - Are conjugated lipids in which the lipid part (e.g. cholesterol, phospholipids or triglycerides) combines with protein part. (water soluble substances and can be transported in the plasma) - Importance of plasma lipoproteins: Blood lipids are water insoluble substance, thus cannot be transported in the plasma , they are conjugated with proteins to form lipoproteins which are converted into water soluble substances and can be transported in the plasma HDL & LDL  Cholesterol O Cholesterol is an animal sterol, contains steroid nucleus and 27 carbons, O It consists of four fused rings and an alcohol hydroxyl groupat C-3 so it is classified as sterols. Biomedical importance: Questions 1. Give an account on rancidity 2. Write 3 important phospholipids and their structure References: 1 Lippincott’s: Illustrated Review Biochemistry. 2 Harpers Illustrated Biochemistry Thank You SUE