Lipids Chemistry PDF

# Lipids Chemistry ## Definition: Lipids are a group of organic compounds insoluble in water (hydrophobic), but soluble in non-polar solvents such as ether, acetone, and chloroform. ## Why to study lipid? 1. Source of energy: They yield twice the energy produced by the same weight of carbohydrate...

# Lipids Chemistry ## Definition: Lipids are a group of organic compounds insoluble in water (hydrophobic), but soluble in non-polar solvents such as ether, acetone, and chloroform. ## Why to study lipid? 1. Source of energy: They yield twice the energy produced by the same weight of carbohydrates or proteins (in absence of Carbohydrates) 2. Energy store in adipose tissue serve as. ## Classification of Lipids ### Simple Lipid * **Formed of:** * fatty acids + * fatty alcohol * **Example:** Fats and Oils ### Compound Lipid * **Formed of:** * lipid part + * non-lipid part * **Example:** 1. Phospholipids 2. Glycolipids 3. Sulpholipids 4. lipoproteins ### Derived Lipids * **Derived from:** substances derived from simple lipids and compound lipids by hydrolysis * **Example:** 1. Fatty acids 2. glycerol 3. Steroids ## 1. Simple Lipids ### **Definition:** They are esters of fatty acids and fatty alcohol. R- COOH + HO-R1 = RCOOR1 + H2O Fatty acid + Alcohol = Ester + Water #### **Example:** * **Fats and oils:** * They are esters of fatty acids with glycerol (Triglycerides) * Triglycerides formed of: Glycerol + 3 Fatty acids * **glycerol** * H * H - C - OH * H - C - OH * H - C - OH * H * **3 fatty acids** * OH - C - R1 * OH - C - R2 * OH - C - R3 * **triglycerides** * H * H - C - O - C - R1 * H - C - O - C - R2 + 3H2O * H - C - O - C - R3 * H * H2O is released #### Glycerol * It is a polyhydric alcohol containing 3 OH groups. * **Importance of glycerol (Uses)** 1. **In Treatment of:** * A) coronary heart disease like angina (act as Vasodilator) nitroglycerin * B) glaucoma due to its ability to dehydrate tissue from its content of water * CH2 - OH * CH - OH * CH2 - OH 2. **In Pharmaceutical and cosmetic preparations** 3. **As explosive:** in the form of trinitroglycerin #### Fatty Acids (FAs) * Fatty acids are usually monocarboxylic straight aliphatic chains with a methyl group at one end (called the w-carbon) and a carboxyl group at the other end. * **Carboxylic end** * H * H H H H H H H H H * I I I I I I I I I I * C - C - C - C - C - C - C - C - C - C - H * H H H H H H H H H H * **Omega end** * They are further classified into saturated and unsaturated fatty acids according to the absence or presence of a double bond. ## 2. Compound Lipids * **Definition:** They are lipids conjugate with non lipid part (other groups) * **They include** * A. Phospholipids: (lipid+phosphoric acid). * B. Glycolipids: (lipid + carbohydrate) * C. Lipoproteins: (lipid + protein). * D. Sulpholipids: (lipids + sulphate). ### A. Phospholipids * **Definition:** Type of compound lipids formed of lipid and non-lipid (phosphoric acid) * **Phospholipids** * **Lipid Part** * FA * Alcohol * **Non-Lipid Part** * Phosphoric acid * Nitrogenous Base * 1. Choline * 2. Ethanolamine/serine * 3. Sphingosine * **Phosphatidic Acid** * O * CH2OCR1 * R2COCH O * 0-0-0 * CH2OPO * **Types** * **2-Lecithin (phosphatidyl choline)** * **Nitrogenous Acid** * Choline * **Base** * **Function** * 1. in the cell membrane. Most abundant PLs. * 2. lipotropic factor (Prevent accumulation of lipids in the liver). * 3. Lung surfactant (Prevent lung collapse) * **Structure** * H2C - O - C - R * HC - O - C - R * HC - O - P - OCH2CH2N(CH3)3 * **3- Cephalin** * **Nitrogenous Acid** * Phosphatidic acid * **Base** * Ethanolamine or serine * **Function** * Important for blood coagulation as it enters in the structure of thromboplastin, which is essential for blood clotting. * **Structure** * H2C - 0 - C - R * HC - O - C - R * HC- O - P - OCH2CH2NH3 * **4-Sphingomyelin** * **Nitrogenous Acid** * Phosphatidic acid * **Base** * Sphingosine & Choline * **Function:** * Abundant in the nervous system in the myelin sheath. ### B. Glycolipid * **Definition:** Type of compound lipids formed of lipid and non-lipid (carbohydrates). * **Glycolipids** * **Lipid Part** * FA * Alcohol * **Non-Lipid Part** * Carbohydrate * Sphingosine Base * **Function** * 1. They are present mainly in the nervous tissues ie. brain and nerves. * 2. They act as electric insulators of nerve impulses. ### C. Lipoproteins * **Definition:** These are compound lipids formed of lipid part (Triglycerides, cholesterol or phospholipids) and protein part (Apolipoprotein). * **Lipoproteins** * **Lipid Part** * Phospholipid * Cholesterol * Triglyceride * **Non-Lipid Part** * Protein (Apoprotein) * **Structure** * **Functions** * 1. Structure of the cell membrane. * 2. Lipid transport in the blood #### Types * **1. Chylomicrons** * **Site of synthesis:** Small intestine * **Structure:** Mainly triglycerides, * **Function:** Transport of exogenous dietary triglycerides from the small intestine to the tissue. * **2. VLDL (Very Low-Density Lipoprotein)** * **Site of synthesis:** Liver * **Structure:** Mainly triglycerides, * **Function:** Transport of endogenous triglycerides from the liver to the tissue. * **3. LDL (Low Density Lipoprotein)** * **Site of synthesis:** Blood * **Structure:** Mainly cholesterol * **Function:** Transport of cholesterol from the liver to the peripheral tissues. * **4. HDL (High Density Lipoprotein)** * **Site of synthesis:** Liver * **Structure:** Mainly proteins & phospholipids * **Function:** Transport of cholesterol from the tissues to the liver. Retrograde (reverse) cholesterol transport ## 3. Derived Lipids * **These are:** 1. substances derived from simple lipids and compound lipids by hydrolysis * a. Fatty acids * b. Glycerol 2. and substances related to lipids as steroids * a. Cholesterol (All of them contain a steroid nucleus) * b. Steroid hormones (sex hormones) * c. Vitamin D * d. Bile acids and salts ## Clinical applications of Lipid chemistry ### 1 - Fatty Liver & lipotropic factors * **Pathogenesis:** It is an abnormal condition characterized by increasing deposition of lipids, mainly TG in the liver cells that may cause on the long run fibrotic changes and impaired liver function * **Normal fat content of liver:** is about 5% of its weight and is mainly phospholipids, but in fatty liver it may reach 20-30% and is mainly in the form of neutral fat. #### Causes of fatty liver: 1. Increased fat and/or Carbohydrates in diet. 2. Increased metabolism of fat from adipose tissue to liver cell. 3. Decreased mobilization of fat from liver to blood. #### Lipotropic factors * **These are substances that protect against and cure fatty liver. ** * **Phospholipids like lecithin act as a lipotropic factor and protect against fatty liver because they are easily mobilized from liver and less liable to deposition in liver** ### 1- Phospholipids and lung surfactants * **Lung surfactants are substances synthesized and secreted from the lung alveoli** * covers the alveolar surface→↓ surface tension in the alveoli decrease the pressure needed to re-inflate alveoli→prevent lung collapse * **lung surfactant is formed mainly of Lecithin (phospholipids) inside lung alveoli** * In pre-mature infant the lung alveoli do not secrete surfactant in sufficient amount→lung collapse happened * **Deficiency of Lecithin:** In pre-mature infant the lung alveoli do not secrete lecithin in sufficient amount→ leads to lung collapse→ Respiratory distress syndrome * **Respira** * **Lack of surfactant** * **Alveoli with surfactants** * Uniform inflation of lung * **Alveoli with lack of surfactants** * Collapsed lung