Medical Biochemistry for Physiotherapy Students PDF

Medical Biochemistry for Physiotherapy Students  Medical Biochemistry for Physiotherapy Students Harpreet Kaur Assistant Professor Department of Bioche...

Medical Biochemistry for Physiotherapy Students  Medical Biochemistry for Physiotherapy Students Harpreet Kaur Assistant Professor Department of Biochemistry Gian Sagar Medical College and Hospital Ram Nagar, Banur Dist. Patiala (Punjab), India Jagmohan Singh Principal and Professor Gian Sagar College of Physiotherapy Ram Nagar, Banur Dist. Patiala (Punjab), India ® JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD New Delhi Ahmedabad Bengaluru Chennai Hyderabad Kochi Kolkata Lucknow Mumbai Nagpur Published by Jitendar P Vij Jaypee Brothers Medical Publishers (P) Ltd Corporate Office 4838/24, Ansari Road, Daryaganj, New Delhi 110 002, India Phone: +91-11-43574357 Registered Office B-3, EMCA House, 23/23B Ansari Road, Daryaganj, New Delhi 110 002, India Phones: +91-11-23272143, +91-11-23272703, +91-11-23282021, +91-11-23245672 Rel: +91-11-32558559 Fax: +91-11-23276490, +91-11-23245683 e-mail: [email protected] Visit our website: www.jaypeebrothers.com Branches 2/B, Akruti Society, Jodhpur Gam Road Satellite Ahmedabad 380 015 Phones: +91-79-26926233, Rel: +91-79-32988717 Fax: +91-79-26927094 e-mail: [email protected] 202 Batavia Chambers, 8 Kumara Krupa Road, Kumara Park East Bengaluru 560 001 Phones: +91-80-22285971, +91-80-22382956, +91-80-22372664 Rel: +91-80-32714073 Fax: +91-80-22281761 e-mail: [email protected] 282 IIIrd Floor, Khaleel Shirazi Estate, Fountain Plaza, Pantheon Road Chennai 600 008 Phones: +91-44-28193265, +91-44-28194897, Rel: +91-44-32972089 Fax: +91-44-28193231 e-mail: [email protected] 4-2-1067/1-3, 1st Floor, Balaji Building, Ramkote Cross Road Hyderabad 500 095 Phones: +91-40-66610020, +91-40-24758498 Rel:+91-40-32940929 Fax:+91-40-24758499, e-mail: [email protected] No. 41/3098, B & B1, Kuruvi Building, St. Vincent Road Kochi 682 018, Kerala Phones: +91-484-4036109, +91-484-2395739, +91-484-2395740 Fax: +91-844-2395740 e-mail: [email protected] 1-A Indian Mirror Street, Wellington Square Kolkata 700 013 Phones: +91-33-22651926, +91-33-22276404, +91-33-22276415 Rel: +91-33-32901926 Fax: +91-33-22656075, e-mail: [email protected] Lekhraj Market III, B-2, Sector-4, Faizabad Road, Indira Nagar Lucknow 226 016 Phones: +91-522-3040553, +91-522-3040554 Fax: +91-522-3040553 e-mail: [email protected] 106 Amit Industrial Estate, 61 Dr SS Rao Road, Near MGM Hospital, Parel Mumbai 400012 Phones: +91-22-24124863, +91-22-24104532, Rel: +91-22-32926896 Fax: +91-22-24160828, e-mail: [email protected] “KAMALPUSHPA” 38, Reshimbag, Opp. Mohota Science College, Umred Road Nagpur 440 009 (MS) Phone: Rel: +91-712-3245220, Fax: +91-712-2704275 e-mail: [email protected] USA Office 1745, Pheasant Run Drive, Maryland Heights (Missouri), MO 63043, USA Ph: 001-636-6279734 e-mail: [email protected], [email protected] Medical Biochemistry for Physiotherapy Students © 2008, Harpreet Kaur, Jagmohan Singh All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the authors and the publisher. This book has been published in good faith that the material provided by authors is original. Every effort is made to ensure accuracy of material, but the publisher, printer and authors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only. First Edition : 2008 ISBN 978-81-8448-379-6 Typeset at JPBMP typesetting unit Printed at Gopsons Papers Ltd., A-14, Sector 60, Noida  Dedicated to Our Parents, Teachers, Friends and Students  Foreword In modern days of advanced medical care, Biochemistry has attained a key position in the field of diagnosis and prognosis of diseases. Physiotherapy is a highly upcoming branch of medical sciences. There is a great role of Biochemistry in Physiotherapy. I appreciate the meritorious work done by Harpreet Kaur and Jagmohan Singh in writing this book Medical Biochemistry for Physiotherapy Students. This book will definitely help the students of Physiotherapy to study the subject of Biochemistry better. I congratulate both of them for successful completion of this work and wish this book a great success. Dr Kamaljit Singh Professor and Head Department of Biochemistry Gian Sagar Medical College and Hospital Banur, Dist. Patiala Chief Executive Officer Gian Sagar Educational and Charitable Trust HO: SCO 109-110, Sector 43-B Chandigarh  Foreword It gives me immense pleasure to write foreword for the book titled Medical Biochemistry for Physiotherapy Students authored by Harpreet Kaur and Jagmohan Singh. This book is a much needed work in the absence of a comprehensive explanatory textbook written for degree level Physiotherapy students. In my opinion, Medical Biochemistry for Physiotherapy Students lives up to the promise of its title, and I am delighted that the authors found the time and dedication needed to write this book which will enable them to share their experience as teachers of Physiotherapy. I appreciate both of them for successful completion of the book. Dr MS Sohal Professor Department of Sports Sciences Punjabi University Patiala  Preface The book titled Medical Biochemistry for Physiotherapy Students has been designed to cater to the long felt needs of students of physiotherapy. The book is also useful for professionals, teachers, doctors, rehabilitation professionals, other paramedics and public in general. The book is developed in a simple and concise format that is easily and readily understandable. The clear, readable type and bold headings make the text easy to comprehend and follow. The book is adequately illustrated with diagrams and tables to assist the students in readily grasping the essential points. The concepts in this book are presented in a simple and straight-forward style. Illustrations and examples have been frequently used to clarify the topics in detail and are further explained as a concept. We hope that the book will provide complete guidance to the students. The book is also useful for teachers, nursing students and students of other allied courses. Harpreet Kaur Jagmohan Singh  Acknowledgements Compilation of such a comprehensive work cannot be done single handedly. The following persons have also been an invaluable source of opinions and comments. Thanks goes to all of them for their encouragement and support: Dr MS Sohal, Professor, Dept. of Sports Sciences, Punjabi University, Patiala. Dr Kamaljit Singh, Professor and Head, Dept. of Biochemistry, Gian Sagar Medical College and Hospital, Banur, Patiala. Dr Minni Verma, Professor, Dept. of Biochemistry, Gian Sagar Medical College and Hospital, Banur, Patiala. Dr Sukhdev Singh, Vice Principal, Desh Bhagat Dental College, Muktsar. Dr Amrit Kaur, Professor and Head, Dept. of Biochemistry, Adesh Institute of Medical Sciences and Research, Bathinda. Dr RL Mattoo, Professor, Dept. of Biochemistry, Adesh Institute of Medical Sciences and Research, Bathinda. Dr Paramvir Singh, Lecturer, Dept. of Sports Sciences, Punjabi University, Patiala. In preparing a textbook like this, I have utilized the knowledge of a number of stalwarts in my profession and consulted many books and journals. I wish to express my appreciation and gratitude to all of them including the related authors and publishers. My special thanks to Shri JP Vij, CMD, M/s Jaypee Brothers Medical Publishers (P) Ltd. and his whole team for publishing this book.  Contents 1. Introduction......................................................................................................................... 1 2. Water and Electrolytes...................................................................................................... 6 3. Chemistry of Carbohydrates......................................................................................... 12 4. Chemistry of Lipids......................................................................................................... 21 5. Chemistry of Amino Acids and Proteins................................................................... 28 6. Chemistry of Nucleotides and Nucleic Acids.......................................................... 37 7. Enzymes............................................................................................................................. 43 8. Vitamins............................................................................................................................. 53 9. Bioenergetics..................................................................................................................... 69 10. Digestion and Absorption.............................................................................................. 74 11. Metabolism of Carbohydrates...................................................................................... 82 12. Metabolism of Lipids.................................................................................................... 100 13. Metabolism of Proteins................................................................................................ 109 14. Minerals........................................................................................................................... 117 15. Fluid and Electrolyte Balance and Imbalance........................................................ 124 16. Biophysics........................................................................................................................ 128 17. Metabolism of Specialized Tissues.......................................................................... 135 18. Hormones......................................................................................................................... 143 19. Diet and Nutrition......................................................................................................... 158 20. Radioactivity and Radioisotopes............................................................................... 165 21. Normal and Abnormal Constituents of Urine........................................................ 170 Index................................................................................................................................... 177  Chapter 1 Introduction INTRODUCTION TO BIOCHEMISTRY Biochemistry can be divided into four main branches: Biochemistry is the science which deals with 1. Medical Biochemistry the chemistry of living organisms, both plants 2. Animal Biochemistry and animals. 3. Plant Biochemistry Cell is the structural unit of all forms of 4. Biochemistry of Micro-organisms. life. Although protoplasm of cell is different Medical Biochemistry deals with the in each kind of animal and plant cell but the following with which the medical students chemical composition, organization and are mainly concerned. i.e. chemistry of tissues processes occurring in each type is similar in and foods, digestion and absorption, respi- many respects. ration, blood, cell membrane and physical The relationship of the living beings to chemistry, tissue metabolism, glands, excre- their environment; the processes by which an tion, biochemical disorders in various exchange of chemical substances takes place diseases etc. between the living organism and its environ- STRUCTURE AND FUNCTION OF ment through digestion, absorption and CELL CONSTITUENTS excretion; the processes by which the Cells are the smallest structural and functional absorbed materials are utilized for synthetic units of all living organisms. The cells of the reactions leading to growth and development living kingdom are divided into two cate- of tissues; the metabolic breakdown of the gories: materials to supply energy; the mechanisms 1. Prokaryotic cells which regulate with precision all these 2. Eukaryotic cells processes by means of hormonal and neuro- Prokaryotic cells lack a well defined regulatory stimuli – all these come under the nucleus and possess simple structure. These purview of biochemistry. include various bacteria. 2 Medical Biochemistry for Physiotherapy Students Eukaryotic cells possess a well defined Cells nucleus and are more complex in their structure and function. The higher organisms (animals and plants) are composed of Tissues eukaryotic cells. We are discussing eukaryotic cells in detail. Cells when grouped together forms tissues Organs which perform specialized functions. Tissues when grouped together forms organs and different organs forms organ systems e.g. Organ System digestive system which is responsible for Fig. 1.1: Cell and organ system taking in, digesting and absorbing food and involves a number of organs including the stomach and intestines (Fig. 1.1). They include: A cell consists of plasma membrane inside 1. Nucleus which there are a number of organelles 2. Mitochondria floating in a watery fluid called cytosol (Fig. 3. Ribosomes 1.2). Organelles are small structures with 4. Endoplasmic reticulum (ER) highly specialized functions. 5. Golgi apparatus Fig. 1.2: Structure of a cell  Introduction 3 6. Lysosome The membrane proteins perform several 7. Centrioles functions: 8. Microfilaments They give the cell its immunological 9. Microtubules identity. They can act as specific receptors for 1. Plasma Membrane hormones and other chemical messengers. The boundary of every cell has a thin mem- Some are enzymes. brane of thickness 75Å units. This is known Some are involved in transport across the as unit membrane or plasma membrane. membrane. The most important function of biologic The plasma membrane consists of two membranes is to restrict the exchange of layers of phospholipids (fatty substance) with substances among various compartments. some proteins embedded in them (Fig. 1.3). Thus, different types of body fluids are Those that extend all the way through the separated from each other by different membrane may provide channels that allow membranes. the passage for example electrolytes, non-lipid soluble substances, etc. 2. Nucleus The phospholipids molecules have a head It is a spherical or oval organelle. Within the which is hydrophilic (attracting water) and a nucleus, hereditary units of the cell called tail which is hydrophobic (water repelling). genes are present which control cellular struc- The phospholipids bilayer is arranged like a ture and direct many cellular activities. The sandwich with the hydrophilic heads aligned nuclear genes are arranged in a single file on the outer surfaces of the membrane and along structures termed chromosomes. the hydrophobic tails forming a central water Human body cells have 46 chromosomes. repelling layer. These differences influence Each body cell contains a nucleus except red the transfer of substances across the mem- blood cells. brane. The nucleus is contained in a membrane similar to the plasma membrane but it has tiny pores through which some substances can pass between it and the cytoplasm i.e. the cell excluding the nucleus. Nucleoli are present inside the nucleus. They are clusters of proteins, DNA, RNA that are not enclosed by a membrane. Nucleoli are the sites of assembly of ribosomes and contain a type of RNA called ribosomal RNA (Fig. 1.4). 3. Mitochondria These are the largest components in cyto- Fig. 1.3: Structure of plasma membrane plasm. These are described as the power 4 Medical Biochemistry for Physiotherapy Students of ATP is most efficient in the final stages of cellular respiration. This is called oxidative phosphorylation, requiring the presence of oxygen. 4. Ribosomes These are tiny granules composed of RNA Fig. 1.4: Structure of nucleus and proteins. They are also found on the outer surface of rough endoplasmic reticulum house of the cell and each cell may contain (RER). Bacterial ribosomes consists of two from 50 to 2500 mitochondria depending on subunits of unequal size, one of sedimentation the respiratory activity of the cell. The cells coefficient of 50S and other of 30S. In of skeletal muscle, kidney and liver contain eukaryotes, 80S ribosome is found (60S and large amount of mitochondria while those of 40S). They synthesize proteins from amino heart muscle contain less. acids using RNA as the template. It has two membranes – the outer mem- brane and the inner membrane. The outer 5. Endoplasmic Reticulum membrane is smooth while the inner mem- These are a series of membranous canals in brane is folded to form ridges or cristae which the cytoplasm. They are of two types: extend into the matrix of the mitochondria. a. smooth endoplasmic reticulum (SER) Elaborate folds of the cristae provide an b. rough endoplasmic reticulum (RER) enormous surface area for a series of chemical Smooth endoplasmic reticulum synthesizes reactions called cellular respiration. Two lipids and steroid hormones and is also spaces – intercristae space and the matrix associated with detoxification of some drugs. space are thereby developed. The matrix Rough endoplasmic reticulum is site of space is rich in enzymes (Fig. 1.5). synthesis of proteins that are extruded from cells i.e. enzymes and hormones that pass out of their parent cell to be used by other cells in the body. 6. Golgi Apparatus Fig. 1.5: Structure of mitochondria This consists of stacks of closely folded flattened membranous sacs. It is present in Mitochondria are involved in cellular all cells but is larger in those cells that respiration, the process by which chemical synthesize and export proteins. The proteins energy is made available in the cell. This is in move from the ER to the golgi apparatus the form of adenosine triphosphate (ATP). where they are packaged into secretory ATP is a high energy compound. Synthesis vesicles, sometimes called secretory granules.  Introduction 5 The vesicles are stored and when needed sible for equal distribution of the characters they move to the plasma membrane, through in the offspring. which the proteins are exported. 9. Microfilaments and Microtubules 7. Lysosomes These are contractile structures in the cyto- They are oval or spherical membrane bound plasm involved in the cell and of organelles bodies formed by the golgi apparatus. They within the cell, the movement of cilia (small contain a variety of enzymes involved in projections from the free surface of some cells) breaking down fragments of organelles and and the organization of proteins in the plasma large molecules (e.g. RNA, DNA, carbo- membrane. They also maintain the charac- hydrates, proteins) inside the cell into smaller teristic shape of the cell. particles that are extruded from the cell as waste materials. Lysosomes in WBC contain 10. Cytoplasm enzymes that digest foreign materials such The cytoplasm is the structure less material as microbes. filling the rest of the cell (aqueous matrix) in which all the cell components float. It is a 8. Centrioles colloidal solution of proteins containing nearly These are two short, cylindrical structures 70% of water besides both organic and known to exist on either side of the nucleus inorganic substances such as glucose, potas- at right angles to each other. They are not sium, magnesium etc. The cytoplasm also bound by any membrane. They help in the contains a small amount of RNA and the equal division of the chromosomes by taking enzymes for glycolysis, gluconeogenesis and them apart and they are, therefore, respon- HMP shunt.  Chapter 2 Water and Electrolytes WATER Properties Water is the most abundant of all chemical 1. Water is colourless, odourless but in larger compounds and it exists in the form of solid, masses has a blue tinge due to the presence liquid and gas. of the finely divided material. 2. Water at sea level freezes at 0ºC or 32ºF Sources and boils at 100ºC or 212ºF. 3. On freezing, water rapidly expands and 1. It occurs in the form of ice – vast areas of increases its volume by nearly 100%. It the colder region. becomes less dense and floats on water. 2. It occurs in the liquid state – 5/7th of 4. The volume of steam is produced about earth’s surface. 1700 times larger than the original volume 3. Soil contains water which is necessary for of water. Confining this steam under plant life. pressure in an autoclave raises the boiling 4. Body is 2/3rd water. point of water and hence increases the 5. It occurs in food in varying quantities. temperature. Necessity of Water 5. It is an excellent universal solvent. Life cannot exist without water, e.g. the Chemical Properties human body without water – its muscles will 1. It is very stable compound and even when refuse to function, food would not be heated to 2500ºC, only a small percentage digested, elimination of waste and the of water molecules dissociate into hydro- building of new tissue would stop and gen and oxygen and these elements reunite regulation of body temperature will be so on as the temperature is lowered but it disturbed. can be decomposed by an electric current.  Water and Electrolytes 7 2. Water reacts with many compounds to Hard Water break them into simpler substances by the The water containing the bicarbonates and process called hydrolysis e.g. digestion of sulphates of calcium and magnesium is called carbohydrates, fats and proteins. as hard water. 3. Water combines directly with many Hardness is of two types: compounds to form crystalline substances 1. Temporary hard water called hydrates. Plaster of Paris when 2. Permanent hard water mixed with water sets to a hard mass and it is used in making surgical casts. Temporary Hard Water This water contains the bicarbonates of calcium and magnesium and it can be softened by boiling because heat changes the soluble bicarbonates into insoluble carbonates of calcium and magnesium. The water which assists in formation of crystals is called water of crystallization or water of hydration. Some crystalline sub- stances contain no water of hydration. These are called as anhydrous compounds e.g. sugar, salt. When a compound takes up atmospheric water, it is called deliquescent e.g. calcium chloride. Permanent Hard Water This contains chlorides and sulphates of Impurities of Water sodium and magnesium. It can be softened Naturally occurring water contains more or by adding caustic soda, slaked lime and by less foreign matter derived from the soil. special processes. This foreign matter is either mineral or organic matter and it may be either dissolved or suspended in the water. Depending upon the mineral matter found in water it is classified as: 1. Soft water 2. Hard water Purification of Water Soft Water Water contains organic impurities such as The water which contains little or no mineral sewage, refuse and inorganic impurities like matter and lathers easily is called as soft water. salts, bicarbonates, chlorides and sulphates 8 Medical Biochemistry for Physiotherapy Students of calcium, magnesium, iron, lead etc. and also 3. Water keeps various surfaces moist such has dissolved gases like nitrogen and carbon as the mucous membrane of the nose, eyes dioxide. Pathogenic bacteria may also be and throat and prevents discomfort. It also present. moistens the joint and act as the solvent in the large intestine helping in the elimi- Methods of Purification nation of faeces. 4. Water acts as a temperature regulator by 1. Distillation: Boiling water and condensing equalizing temperature of various parts of the resulting steam in a different container the body through the circulating fluid. The is called as distillation. It is the most regulation of the body temperature is effective method of purifying water. accomplished largely by the skin – by 2. Boiling: Water may be made fit for controlling the amount of heat lost from drinking purposes by boiling. This process the body through altering the amount of does not remove any dissolved solid blood sent to the surface and the amount matter. But kills the disease producing of perspiration. The major portion of heat micro-organisms. lost from the body is removed through 3. Filtration: The suspended matter in water the evaporation of water from skin. such as clay and undissolved organic 5. It helps in digestion. It is the principal matter may be removed by filtration. It is constituent of the secretion of glands a very economical method of purifying (digestive juices). It is essential in rapid water for drinking purposes. chemical action and the absorption of 4. Aeration: When exposed to the air, water digested foods. It is one of the reacting in time purifies itself. The oxygen of the substances in many chemical changes air dissolves in the water, acts chemically (hydrolysis). Practically, all the chemical on the bacteria and destroys them. processes which take place during diges- tion and many of these which occur in the Functions/Physiologic tissues are of this nature i.e. breaking Importance of Water down of complex substances into simple 1. It is a component of protoplasm and substances by means of chemical reaction tissues. It keeps most of the constituents with water. Enzymes speed up these of the cell contents (protoplasm) in solu- reactions. tion so that chemical changes essential to maintain cell function can take place. It ELECTROLYTES maintains the proper degree of dilution The substances which conduct the electric in the tissue fluids which bathe the cells, a current in solution are called electrolytes e.g. condition necessary for their functioning. HCl, NaCl and the substances which fail to 2. It provides fluid medium for transporting pass the current are called as non electrolytes food materials away from the tissues. It is e.g. sugar. necessary for the proper excretion of So, electrolytes include acids, bases and waste material many of which are excreted salts and non electrolytes include pure water, in urine. alcohol and sugar.  Water and Electrolytes 9 The body contains electrolytes and is a 2. Action on indicators: Many coloured conductor of electricity. Its advantage is taken compounds changes colour in the presence by using the electrocardiograph, an instru- of acids. So these are used as an indicators ment which measures the variation in the for detecting acids e.g. blue litmus dye feeble current released during the contraction which changes to a red colour in the pre- and relaxation of the heart. sence of an acid. The common acids HCl, HNO3, H2SO4 and 3. Action on metals: When active metals such the bases NaOH and KOH are ionized into as sodium, magnesium or zinc are placed in acid solutions, they react chemically and water, so they are called strong electrolytes. hydrogen gas is usually liberated. Because Other acids and bases such as acetic acid and of this corrosive action, the acids are kept ammonium hydroxide show only a small in glass containers. degree of ionization, so they are called as 4. Action on oxides and hydroxides: Many acids weak electrolytes. react with the oxides and hydroxide of metals. Neutralization is a useful reaction Acids for counteracting the action of an acid or Acids give hydrogen ions (H+) in solution. a base. Many of our food contain acids and they are 5. Action on carbonates and bicarbonates: constantly forming in the body. The gastric Whenever an acid solution comes into juice and the urine are acid fluids. contact with a carbonate or bicarbonate, effervescence comes out due to the Classification of Acids evolution of CO2 gas. 6. Action on tissues: The physiological action 1. Organic acids of strong, concentrated acids upon the 2. Inorganic acids tissue is to destroy the tissues through All of the organic acids contain carbon and corrosive action. But much diluted acids they are often derived from plant and animal only abstract water from the tissues. So in sources. Organic acids are weak. Its examples fevers, mild acids may be used to diminish are acetic acid C2H4O2, citric acid C6H8O7, the thirst because they stimulate the flow lactic acid C3H6O3, tartaric acid C4H6O6, etc. of saliva. The important inorganic acids are known as mineral acids. Its examples are hydrochloric Precautions While Handling Acids acid HCl, nitric acid HNO3, sulphuric acid and Bases H 2 SO 4 , boric acid H 3 BO 3 , carbonic acid Acids and bases are designated as corrosive H2CO3 etc. chemicals. Corrosive chemicals are those which when ingested, inhaled or allowed to Properties of Acids come in contact with skin can destroy living 1. Sour taste: When acid is dissolved in water, tissue. E.g. acids like sulphuric acid (H2SO4), it gives sour taste to the water e.g. sour nitric acid (HNO3) and bases like sodium taste of lemons, oranges, grapes is due to hydroxide (NaOH), potassium hydroxide citric acid. (KOH). 10 Medical Biochemistry for Physiotherapy Students Storage 4. Lactic acid: It checks growth of bacteria in large intestine. These should be stored at low level to avoid 5. Hypochlorous acid: It acts as a disinfectant, injury which could be caused if these chemi- antiseptic and bleaching agent. cals were accidently knocked off a shelf. Do 6. Boric acid: It acts as an antiseptic for not store KOH or NaOH in a bottle having a inflamed mucous membranes in the eyes, ground glass stopper because these chemicals nose or mouth. absorb carbon dioxide from the air forming carbonates, which can cement the stopper in Bases the bottle. A base is a compound which gives hydroxyl Safe Use ions (OH–) in water solution. 1. Never mouth pipette with a corrosive Properties chemical. The accidental swallowing of it 1. Soapy feeling: Whenever strong base is can cause severe internal injury. dissolved in water, the solution feels 2. Always pour a corrosive chemical at below the eye level, slowly and with a great care slippery or soapy. to avoid splashing. 2. Bitter taste: They have bitter taste. 3. Wear suitable protective gloves when 3. Action on indicators: Bases reverse the opening a container of a corrosive chemi- colour change which acids produce with cal and when pouring it. Place a cloth over indicators. Bases turn red litmus paper the neck and cap of the container when blue while acids turn blue litmus to red. opening it. 4. Reaction with acids: They react with acids 4. Dissolve a solid corrosive chemical such to form salts. This is very important as NaOH in water with great care, mixing function in the body for maintaining the in small amounts at a time to dissipate the alkaline reaction in the blood. heat produced. 5. They react with fats to form soaps. Strong 5. When diluting concentrated acids parti- bases destroy tissues by attracting the cularly H 2SO 4, always add acid to the water, dissolving the albumin and reacting water. Never add water to the acid. with the fats. Adding water to acid can produce 6. They are used for removing certain stains. sufficient heat to break a glass container. Some Bases of Importance 6. Always use a strong carrier to transport bottles of corrosive chemicals. 1. Sodium hydroxide: It is also known as caustic soda. It is used as a household Some Acids of Importance article as a drastic cleanser because it 1. Hydrochloric acid: It helps in gastric reacts with grease to make soap. Commer- digestion of proteins. It also acts as an cially it is used in the manufacture of hard antiseptic by destroying fermentation of soaps. bacteria in the intestinal tract. 2. Calcium hydroxide: It is also known as 2. Nitric acid: It acts as a coagulant in testing slaked lime. Lime water is used in for albumin in the urine. medicine to overcome high acidity in the 3. Boric acid: It acts as an antiseptic for stomach. Lime water is used in diet for inflamed mucous membranes in the eyes, building bones and teeth. It serves as a nose or mouth. special antidote for oxalic acid poisoning.  Water and Electrolytes 11 3. Ammonium hydroxide: In medicine, 4. Essential for life: Salts do not furnish heat ammonium hydroxide is used as a heart or energy, but they are very essential to respiratory stimulant. life because 4. Magnesium hydroxide: In medicine, a thick a. They make up the protoplasm, tissue and suspension known as milk of magnesia is bone structure. used as an antacid. Magnesium compound b. They keep up the elasticity and irrita- is a laxative in its physiological action. bility of the muscles. c. They maintain the neutrality of slightly Salts acid or alkaline condition of the body Salts are formed by a reaction between an secretions, blood and other fluids. acid and a base where a salt and water are d. They assist in maintaining normal osmo- formed. tic pressure conditions. NaOH + HCl ———— > NaCl + H2O Medical Salts Importance of Salts in the Body 1. Sodium chloride: Its common name is common salt. It is used as a saline solution. 1. Formation of salts in the body: Acids are 2. Mercuric chloride: It is used as an antiseptic. constantly being formed in the body. The 3. Calcium sulphate: Its common name is body fluids with the exception of the Plaster of Paris. It is used as casts for gastric juices and urine are alkaline or broken bone. neutral. As a result of neutralization, many Acids, bases and salts are called electro- salts are produced and excreted in the lytes when dissolved in water because they urine, sweat and faeces. ionize into two oppositely charged part called 2. Neutralization in blood: Any change in the ions. normal acidity or alkalinity of the different parts of the human body affects markedly Theory of Arrehenius Ionization every cell and organ for instance. If the alkalinity of the blood is too low (acidosis) 1. The molecules of electrolytes break up in or too high (alkalosis), the heart will be water solution into definite component affected so that it will not pump uniformly. parts called ions. This type of dissociation 3. Buffer action in the body: The process of is called ionization. Non electrolytes do digestion and cell activity produce nume- not ionize. rous substances which enter the blood 2. Some ions are positively charged and stream. These substances may be acidic, others are negatively charged. The some alkaline and neutral. The blood conductance of electricity by solutions of maintains a constant pH which ranges electrolytes is accomplished by the ions. normally from 7.35 to 7.45. This constancy 3. The abnormal effect of electrolytes as of hydrogen ion concentration is possible compared to the non electrolytes in the because of the presence in the blood of same concentration are due to an increase certain molecules and related ions which in the total number of particles as a acts as buffers. consequence of ionization.  Chapter 3 Chemistry of Carbohydrates Carbohydrates are composed of the elements 1. Monosaccharides carbon, hydrogen and oxygen. The name 2. Disaccharides carbohydrates literally mean ‘hydrates of 3. Oligosaccharides carbon’. The empirical formula is (CH2O)n. 4. Polysaccharides Carbohydrates are defined chemically as aldehyde or ketone derivatives of higher Monosaccharides polyhydric alcohols or compounds which These are also known as simple sugars. yield these derivatives on hydrolysis. Monosaccharides are those which cannot be further hydrolyzed into simpler forms. FUNCTIONS OF CARBOHYDRATES Empirical formula is: 1. Carbohydrates are the dietary sources of CnH2nOn energy (4 C/g) for all organisms. They can further be subdivided as follows: 2. Carbohydrates are precursors for many a. Depending on the number of carbon atoms organic compounds (fats, amino acids). it contains like trioses if 3 carbon atoms 3. Carbohydrates (as glycoprotein and are present, tetroses if 4 carbon atoms, etc. glycolipids) participate in the structure of b. Depending on the presence of aldehyde cell membrane and cellular functions. or ketone groups 4. These are storage form of energy for energy in the form of glycogen General Aldosugars Ketosugars Formula 5. These are structural components of many Trioses (C3H6O3) Glyceraldehyde Dihydroxyacetone organisms like the cell walls of bacteria, Tetroses (C4H8O4) Erythrose Erythrulose fibrous cellulose of plants. Pentoses (C 5H10 O5) Ribose Ribulose Hexoses (C 6H12 O6) Glucose Fructose Classification of Carbohydrates Heptoses(C 7H 14O 7) Glucoheptose Sedoheptulose Carbohydrates are divided into four main groups depending upon the number of Thus, trioses with aldehyde group are monomer units present in the molecule: called aldotrioses and trioses with ketone  Chemistry of Carbohydrates 13 group are ketotrioses. Similarly, tetroses with aldehyde group are aldotetroses and tetroses with ketone group are ketotetroses and so on. D-Series and L-Series The D- and L-isomers are mirror images of each other. The orientation of the H and OH groups around the carbon atom just adjacent to the terminal primary alcohol carbon e.g. C-atom 5 in glucose determine the series. If this OH group is on right side, the sugar is of General Properties D-Series and if it is on left side, it belongs to the L-Series. Isomerism Naturally occurring monosaccharides in Compounds that have the same chemical the mammalian tissues are mostly of D-form. formula are called isomers. For example fructose, glucose, mannose and galactose are all isomers of each other, having the same chemical formulae. Therefore, isomerism is exhibited by organic compounds having same molecular formulae. Due to this property, although these compounds have same molecular formulae, they have different physical and chemical properties. The presence of asymmetric carbon in the compound results in the formation of isomers of that compound. Optical Activity of Sugars Asymmetric Carbon Atom All the compounds having asymmetric carbon A carbon atom to which four different atoms atoms can rotate the beam of plane polarized or group of atoms is attached is said to be light and are said to be optically active. An asymmetric. The number of isomers of a compound depends on the number of isomer which can rotate the plane of polarized asymmetric carbon atoms and is given by 2n light to the right is called as dextrorotatory where n indicates the number of asymmetric and is designated as (d) or (+) while the carbon atoms in that compound. Glucose isomer which rotates the plane of polarized contains 4 asymmetric carbon atoms and thus light to the left is called as laevorotatory and has 16 isomers. is designated as (l) or (-). 14 Medical Biochemistry for Physiotherapy Students When equal amounts of dextrorotatory and levorotatory isomers are present in a mixture, the resulting mixture is optically inactive and is said to be a racemic mixture. α – and β – Anomers of Glucose The cyclic structures of glucose is retained in solution, but isomerism takes place about position 1. This is formed by optical rotation, known as mutarotation, by which the posi- tions of –H and –OH groups are changed PROPERTIES OF MONOSACCHARIDES around carbon 1. Example: When D- Glucose is dissolved Physical Properties in water, its specific rotation is +111º. Gra- They are colourless, crystalline compounds, dually, it decreases and remains constant at readily soluble in water and sweetish in taste. +52.5º. These two forms are referred to as α- Their solutions are optically active and exhibit and β- glucose respectively. Blood sugar is the phenomenon of mutarotation. α-β-D-glucose. Chemical Properties Reactions due to aldehyde or ketone groups: 1. Osazone formation: The reducing sugars form characteristic crystals. These are obtained by adding a mixture of phenyl hydrazine hydrochloride and sodium acetate to the sugar solution and then heating it in a boiling water bath for 30 to 45 minutes and allowing to cool slowly. Precipitates are separated and spread on slide for examination under low power of microscope. These compounds have characteristic crystal structures, melting Epimers points and precipitation times. Isomers formed as a result of interchange of Glucosazone crystals are fine, yellow the –OH and –H on carbon atoms 2, 3 and 4 needles in fan shaped aggregates, descri- of glucose are known as epimers. Mannose bed as “bundle of hay”. Glucose, maltose, and galactose are formed by epimerization mannose form the same osazones. of carbons 2 and 4 respectively. In the body, Lactosazone crystals are irregular of epimerization takes place by the enzyme, clusters of fine needles and look like a epimerase. “powder puff”.  Chemistry of Carbohydrates 15 Maltosazone crystals are star shaped and HNO3 compared to sunflower petals. D-Glucose ———> D-Glucosaccharic acid c. Uronic Acids: When an aldo sugar is oxidized in such a way that the primary alcohol group is converted to -COOH group, without oxidation of aldehyde group, a uronic acid is formed. D-Glucose ——> D-Glucuronic acids D-Galactose ——> D-Galactouronic acid This is not possible under laboratory conditions, but readily occurs in living Osazone formation is a useful means of tissues by enzyme action. preparing crystalline derivatives of sugars and are valuable in identification of sugars. Biological Importance 2. Reduction of sugars to form sugar alco- Uronic acids are components of structural hols: The monosaccharides may be redu- material like chondroitin and mucoitin sul- ced to their corresponding alcohols by phuric acids and glycoproteins. Certain toxic reducing agents such as sodium amalgam substances are conjugated with glucuronic or with hydrogen under pressure. Simi- acid in the liver and excreted as less toxic sub- larly, ketoses may also be reduced to form stances. Bile pigments and steroid hormones keto alcohol. For example, that are relatively insoluble, are also conju- 2H gated with glucuronic acid to render them D-Glucose —————> D-Sorbitol more soluble and readily excretable in urine. D-Galactose —————> D-Dulcitol 1. Interconversion of sugars: Glucose, fructose D-Mannose —————> D-Mannitol and mannose are interconvertible in weak D-Fructose —————> D-Mannitol + alkaline solutions such as Ba(OH) 2 or D-Sorbitol Ca(OH) 2. It is because weak alkaline 3. Oxidation of sugars to produce sugar solutions of sugars undergo molecular acids change known as “tautomerization” where a. Mild oxidizing agents like bromine ‘H’ atoms migrate from one carbon to water oxidize the -CHO to a -COOH to another to form “enediol” compounds. All form sugar acids. sugars give the same enediol which Br 2 tautomerizes to all three sugars. This D-Glucose —————> D-Gluconic acid interconversion of related sugars by the action of dilute alkali is referred to as b. Strong oxidizing agents like HNO 3 , “Lobry de bruyn-Van Ekenstein reaction”. Oxidize the -CHO group as well as the 2. Reducing action of sugars: Monosaccharides primary alcoholic group to produce by virtue of their free aldehyde or ketone sugar acids called “saccharic acids” or group in their structure reduce free “aldaric acids”. metallic cations such as Cu 2+ ions in 16 Medical Biochemistry for Physiotherapy Students alkaline solution at high temperature. All Indican = Carbohydrate + Indoxyl the monosaccharides and the two disaccha- (aglycone) rides, maltose and lactose reduce cupric 2. Acetylation or ester formation: The alcohol ions present in Benedict’s reagent and also group of sugars may react with acids to in Fehling’s reagent. Lactose and maltose form esters. Phosphoric acid esters of have free reducing groups hence these are sugars are important as intermediate capable of reducing metallic ions but since products during metabolism. Examples sucrose does not have a free reducing are: Glucose-1 -phosphate, Glucose-6- group, it is a non reducing sugar. phosphate, Fructose-6-phosphate, Galac- tose-1-phosphate, etc. Reactions due to the Alcoholic Groups 3. Dehydration by strong acids: When sugars 1. Glycosides: Glycosides are compounds are treated with concentrated H2SO2 in formed by the condensation reaction cold or on heating with a strong solution between a sugar and alcohol. The carbo- of HCl, pentoses form cyclic aldehyde hydrate residue is attached by an acetal called “furfural” whereas hexoses form linkage of carbon-1 to the -OH group of “hydroxy methyl furfural”. non carbohydrate residue called aglycone. This reaction forms the basis of quanti- The aglycones may be methyl alcohol, tative determination of carbohydrates. glycerol, phenol, hydroquinones, sterols Examples are: Molisch test, Seliwanoff’s and anthraquinones. test, Bial-orcinol test. The glycosides are named according to the SUGAR DERIVATIVES OF carbohydrate they contain. If it contains BIOLOGICAL IMPORTANCE glucose, forms glucoside. If galactose, it forms galactoside and so on. A simple example is the methyl glucoside Amino Sugars (Hexosamines) formed when a solution of glucose in Sugars containing -NH 2 group are called boiling methyl alcohol is treated with 0.5% amino sugars. HCl as a catalyst. a. Glucosamine (2-amino D-glucose): It is a Aglycone: The non carbohydrate portion constituent of mucopolysaccharides and of the glycoside is called the aglycone. mucoproteins such as hyaluronic acid, Glycosides do not reduce alkaline copper heparin and blood group substances. It is sulphate because sugar group is combined, present in the cell walls of fungi and in i.e. aldehyde group is converted to an the shells of crustaceans (lobster, crab, etc) acetal group. as chitin. Hence glucosamine is called Examples “chitosamine”. Cardiac glycosides = Carbohydrate + b. Galactosamine (2-amino D-galactose): It Digoxin (aglycone) occurs in sulphated mucopolysaccharides  Chemistry of Carbohydrates 17 as chondroitin sulphates which are present Examples are: in cartilages, bones, tendons and heart 1. Maltose – It yields two molecules of valves, hence galactosamine is also called glucose on hydrolysis. as chondrosamine. Maltose ———> glucose + glucose 2. Lactose – It yields one molecule of glucose and one molecule of galactose on hydro- lysis. Lactose ———> glucose + galactose 3. Sucrose – It yields one molecule of glucose and one molecule of fructose on hydrolysis Sucrose ———> glucose + fructose The disaccharides are of two types: 1. Reducing disaccharides which have free c. Certain antibiotics such as erythromycin aldehyde or keto group e.g. maltose, contain amino sugars responsible for lactose. antibiotic activity. 2. Non-reducing disaccharides which have Deoxy Sugars no free aldehyde or keto group e.g. sucrose. Deoxy sugars are those in which a hydroxyl group attached to the ring structure has been Maltose replaced by a hydrogen atom. They are obtained on hydrolysis of certain substances Maltose, also known as malt sugar is that are important in biologic processes. An composed of two α- D- glucose units held example is the deoxyribose occurring in together by α (1→4) glycosidic bond. The free nucleic acids (DNA). aldehyde group present on C 1 of second Also found as a carbohydrate of glyco- glucose answers the reducing reactions, proteins is L-fucose and of importance as an besides the osazone formations. inhibitor of glucose metabolism is 2-deoxy- glucose. Disaccharides These are those sugars which yield two molecules of monosaccharides on hydrolysis; they may be same or different. The two units of monosaccharides are It is produced during the course of joined by a glycosidic bond. Empirical formula digestion of starch by the enzyme amylase. is: It is hydrolyzed by the intestinal enzyme Cn(H2O)n-1 maltase to two molecules of glucose. 18 Medical Biochemistry for Physiotherapy Students Sucrose heldtogether by α (1→4) glycosidic bond. The anomeric carbon of C1 glucose is free; hence Sucrose, also known as cane sugar is made lactose exhibits reducing properties and up of α-D-glucose and β-D-fructose. The two forms osazones. monosaccharides are held together by a glycosidic bond (α 1 →β 2 ) between C 1 of α-glucose and C2 of β- fructose. The reducing groups of glucose and fructose are involved in glycosidic bond, hence sucrose is a non reducing sugar and it cannot form osazones. Lactose or milk sugar is an animal disaccharide and is present to the extent of 5% in milk only. It is synthesized in mammary glands and during lactation may appear in urine. It is hydrolyzed by the intestinal enzyme lactase to glucose and galactose. Sucrose or cane sugar is a plant disaccharide and is present in high concentration in sugar Oligosaccharides cane and sugar beet. Sucrose is used for sweetening purpose. It is hydrolyzed by the These are those sugars which yield 3–10 intestinal enzyme sucrase to glucose and monosaccharides on hydrolysis. Examples fructose. include Raffinose – fructose + galactose + glucose Stachyose – 2 molecules of galactose + Invert Sugar glucose +fructose Sucrose is dextrorotatory (+62.5 o ) but its hydrolytic products are laevorotatory because Polysaccharides fructose has a greater specific laevo-rotation These are those sugars which yield more than (-92 o ) than the dextro-rotation of glucose ten molecules of monosaccharides on hydro- (+52.5o). As the hydrolytic products invert the lysis. Empirical formula is: rotation, the resulting mixtures of glucose and (C6H10O5)n fructose (hydrolytic products) is called as invert These are usually tasteless and form sugar and the process is called as inversion. colloid with water. Polysaacharides are of Honey is an example of invert sugar and two types: the presence of fructose accounts for the 1. Homopolysaccharides greater sweetness of honey. 2. Heteropolysacchraides Homopolysaccharides are also known as Lactose homoglycans. These are polymers of same Lactose, also known as milk sugar is made monosaccharide units. Examples are starch, up of β-D-galactose and β-D-glucose glycogen, inulin, cellulose, dextrins, etc.  Chemistry of Carbohydrates 19 Heteropolysaccharides are also known as 3. Inulin heteroglycans. These are polymers of diffe- Inulin is found in tubers and roots of dahlias, rent monosaccharide units. Examples are artichokes and dandelions. It is hydrolysable mucopolysaccharides like heparin, chondriotin to fructose and hence it is a fructosan. No sulphate etc. colour is given when iodine solution is added 1. Starch to inulin solutions. This starch is easily soluble in warm water. It is used in physiologic Starch is stored as a reserve food in cereals investigation for determination of the rate of and tubers of plants. A starch molecule glomerular filtration. contains two polysaccharides; amylase and amylopectin. Amylase consists of D-glucose 4. Dextrins units linked by α-1, 4-glycosidic linkages in the form of a straight chain. Amylopectin is Dextrins are substances formed in the course similar to amylase but also contains α-1, of the hydrolytic breakdown of starch. The 6-glycosidic bonds to form a branched struc- partially digested starches are amorphous. ture. Branching occurs after every 24-30 Limit dextrins that give a red colour when glucose units. tested with iodine are first formed as hydrolysis reaches a certain degree of 2. Glycogen branching. These are called erythrodextrins. Glycogen is also called animal starch as it is As hydrolysis proceeds, the iodine colour is stored in animals in their liver and muscle. It no longer produced. These are the so-called has a structure similar to amylopectin with achroodextrins. Finally, only reducing sugars straight chain of α-1, 4-linked glucose units will appear. and α-1, 6-branched points. Branching occurs after every 12- 18 glucose units making it a 5. Cellulose highly branched molecule with a tree like Cellulose is the chief constituent of the structure. Liver glycogen is readily available framework of plants. It gives no colour with source of glucose during starvation. Glycogen iodine and is not soluble in ordinary solvents. is non-reducing and gives a red colour with It consists of long, straight chains of β-D- iodine. glucopyranose units linked by β (1 ——> 4) Differences between starch and glycogen: bonds. It is not subject to attack by the a. Starch is of plant origin whereas glycogen digestive enzymes of humans because of the is of animal origin. β-linkage. Thus, it is an important source of b. Glycogen is much more branched than the bulk in the diet. starch. In starch, the branching is after every 24 to 30 glucose units, whereas in 6. Chitin glycogen, the branching is after every 8 to 10 glucose units. It is present in the exoskeletons of inver- c. Starch gives blue colour with iodine tebrates like crab shell or insect wings, it is solution whereas glycogen gives red made up of acetylated glucosamine (chito- colour. samine) units. 20 Medical Biochemistry for Physiotherapy Students Heteropolysaccharides mainly in cartilage, bone, cornea, skin, arterial wall, etc. Heteropolysaacharides or heteroglycans or mucopolysaccharides or glycosaminoglycans Dermatan Sulphate Mucopolysaccharides are composed of acetylated glycosamine (aminosugar) and These are made of D-glucuronic acid and L- uronic acid units; some are made up of ioduronic acid. They occur in the skin, aorta, aminosugar and monosaccharide units cardiac valves, tendons, arterial walls. without the presence of uronic acid. They are essential components of tissues present either Keratan Sulphate in free form or in combination with proteins, These are composed of N-acetyl glucosamine known as “mucoproteins or glycoproteins”. and D-galactose. They occur in cornea, Some important mucopolysaccharides are as cartilage, intervertebral discs and loose follows: connective tissues. Hyaluronic Acid Heparin It is made of repeating units of N-acetyl It is a polymer of D-glucosamine and either glucosamine and D-glucuronic acid. It is of the two uronic acids—D-glucuronic acid present in skin, connective tissue, vitreous or L-ioduronic acid. It is present in mast cells humour, synovial fluid and cartilage and acts in lungs, liver, skin and intestinal mucosa. It as a ground substance or connecting sub- acts as an anticoagulant. stance and acts as a lubricant and shock absor- bent. Blood Group Antigens Chondroitin Sulphate These contain peptides or amino acids and These are made of N-acetyl galactosamine carbohydrates. They contain galactosamine, and D-glucuronic acid. They are present glucosamine, fucose, etc.  Chapter 4 Chemistry of Lipids Lipids are a heterogeneous group of com- 5. Lipids are required for the absorption of pounds related, either actually or potentially, fat-soluble vitamins. to the fatty acids. 6. Lipoproteins and glycolipids are essential Chemically, lipids are defined as esters of for maintaining cellular integrity. fatty acids with various alcohols. They have 7. Lipids form important constituent of the common property of being: nervous tissue. 1. Relatively insoluble in water. 2. Soluble in non polar solvents such as ether, Classification of Lipids chloroform, acetone and benzene. Bloor has proposed the following classifi- Because of their insolubility in aqueous cation of lipids: solutions, body lipids are generally found A. Simple Lipids. These are esters of fatty compartmentalized as in the case of mem- acids with various alcohols. brane associated lipids and droplets of triacyl- B. Compound Lipids glycerol in adipocytes or transported by These are esters of fatty acids with alco- plasma in association with protein as lipo- hols but in addition they also contain protein particles. other substituents like carbohydrate, protein, sulphate, phosphoric acid etc. Importance of Lipids C. Derived Lipids 1. Lipids are important dietary constituents. These are obtained by hydrolysis of These give 9 C/g. simple and compound lipids. 2. Lipids are important constituents of the Simple Lipids cell membrane along with the proteins. 3. Lipids serve as a thermal insulator in the These are esters of fatty acids with various subcutaneous tissues and around certain alcohols and are further divided into two sub organs. classes – neutral fats and waxes. 4. Lipids supply so-called essential fatty acids which cannot be synthesized by the body Neutral Fats and are essential in the diet for normal These are esters of fatty acids with glycerol health and growth. and are also known as triglycerides or 22 Medical Biochemistry for Physiotherapy Students triacylglycerol. Triacylglycerol contains three Chemical Properties molecules of fatty acids esterified with one 1. Hydrolysis: Triglycerides are hydrolysed molecule of glycerol. Similarly, monoacyl- to produce free fatty acids and glycerol glycerol and diacylglycerol are also other by the lipases at alkaline pH and in the examples of neutral fats, they contain one, presence of water. The hydrolysis takes and two molecules of fatty acids esterified place in a stepwise manner. Diglycerides with one molecule of glycerol respectively. are formed first, followed by mono- Out of these three, triglycerides are most glycerides and finally the monoglycerides important. are split to free glycerol and fatty acids. Triglycerides can be simple or mixed type. Simple type of triglycerides contain same type of fatty acid residue at all the three carbons e.g. tristearin or tristeroyl glycerol. 2. Hydrogenation: Unsaturated fats can be hydrogenated by the addition of hydro- gen across the double bonds of the fatty Mixed type of triglycerides contains two acids in the presence of nickel as catalyst or three different types of fatty acid residues to give fully saturated fats. The above e.g. 2- stearo- 1,3- oleopalmitin and 1- palmito process is called hardening of oils where- – 2- stearo- palmitin. by vegetable oils are hydrogenated to produce commercial cooking fats. 3. Saponification: The hydrolysis of trigly- cerides by alcoholic potassium hydroxide or by sodium hydroxide is called saponi- fication. The resultant products are glycerol and potassium or sodium salts of Physical Properties of Fats fatty acids known as soaps. 1. They are insoluble in water, but readily soluble in organic solvents like ether, chloroform, benzene etc. 2. They are readily soluble in hot alcohol but slightly soluble in cold. 3. They are tasteless, odourless, colourless and neutral in reaction. 4. Rancidity: The term rancidity is used to 4. Their melting points are low. represent the deterioration of fats and oils 5. The specific gravity of fats is lower than in an unpleasant taste. Rancidity occurs water, so, it floats on water. when fats and oils are exposed to air,  Chemistry of Lipids 23 moisture, light, bacteria, etc. This occurs This classification is based on the type of due to the formation of peroxides at the alcohol present. In glycerophosphatides, double bonds of unsaturated fatty acids. glycerol is the alcohol group. In phospho- Therefore, fats containing unsaturated fatty inositides, inositol is the alcohol group. In acids are more susceptible to rancidity. phospho-sphingosides, sphingol is the alcohol Rancidity can be prevented by the use of group. antioxidants. Antioxidants like tocopherols, The phospholipids include the following: 1. Phosphatidic acid and Phosphatidyl hydroquinone, gallic acid and α-naphthol glycerols are added to the commercial preparations Phosphatidic acid is important as an of fats and oils to prevent rancidity. intermediate in the synthesis of triacyl- glycerols and phospholipids but is not Waxes found in greater quantity in tissues. If the fatty acid is esterified with a mono- Cardiolipin is a phospholipid that is found hydric alcohol of high molecular weight in membranes of mitochondria. It is instead of glycerol, the resulting compound formed from phosphatidyl glycerol. is called a wax. These resemble fats and are 2. Phosphatidyl choline (Lecithin) usually solid. In the human body, the The lecithins contain glycerol and fatty commonest waxes are esters of cholesterol. acids as in simple fats, but they also contain True waxes are esters of higher fatty acids phosphoric acid and choline. The lecithins with cetyl alcohol (C16H33OH) or other higher are widely distributed in the cells of the straight chain alcohols. These are formed as body, having both metabolic and struc- tural functions in membranes. secretions and are mostly protective in Lecithin on hydrolysis give glycerol, fatty function, by many animals. acid, phosphoric acid and choline. Dipalmityl lecithin (DPL) is a very effective Compound Lipids surface effective agent, preventing adhe- These are esters of fatty acids with alcohols rence, due to surface tension, of the inner but in addition, they also contain other surfaces of the lungs. substituents like carbohydrate, protein, sulphate, phosphoric acid, etc. Phospholipids Phospholipids are included in a class of compound lipids. These are the lipids containing, in addition to fatty acids and an Phosphatidyl Ethanolamine (Cephalin) alcohol, a phosphoric acid residue. They also have nitrogen containing bases and other The cephalins differ from lecithins only in that subsituents. ethanolamine replaces choline. If the base is They are divided into three classes: ethanolamine, then it is called phosphatidyl 1. Glycerophosphatides ethanolamine or ethanol amine cephalin. If 2. Phospho-inositides the base is amino acid serine, then it is called 3. Phospho-sphingosides phosphatidyl serine or serine cephalin. 24 Medical Biochemistry for Physiotherapy Students Cephalins on hydrolysis yield glycerol, Glycolipids fatty acids, ethanolamine or serine. Lipids containing carbohydrate moiety are called glycolipids. They contain a special Phosphatidylinositol alcohol called sphingosine or sphingol and They are found in brain, liver, heart and nitrogenous base in addition to fatty acids soyabean. They contain no base but have but do not contain phosphoric acid or inositol in its place. glycerol. These are of two types: a. Cerebrosides Cardiolipin b. Gangliosides It is an important phospholipids of mito- chondrial membrane. It is a diphosphatidyl Cerebrosides glycerol in which two phosphatidic acids are They are present in greater concentration in joined by a molecule of glycerol. These white matter of brain and myelin sheath of phosphatidic acids are particularly rich in the nerve. They comprise of a molecule of fatty polyunsaturated fatty acids especially linoleic acid, an amino alcohol sphingosine and a acid. sugar usually galactose. Sphingomyelins Types Phospholipids containing sphingosine are Four types of cerebrosides are found called sphingomyelins. They contain a depending upon the type of fatty acid present: complex base sphingosine in addition to a. Kerasin – contains lignoceric acid as the phosphoryl choline. A fatty acid is attached fatty acid. to the amino group of the sphingosine. No b. Cerebron - contains hydroxy lignoceric glycerol is present. Sphingomyelins are acid as the fatty acid. present in all tissues especially in brain and c. Nervon - contains nervonic acid as the other nervous tissues. Sphingomyelins on fatty acid. hydrolysis yield sphingosine, fatty acid, d. Oxynervon - contains hydroxy nervonic phosphoric acid and choline. acid as the fatty acid. Functions of Phospholipids Clinical Aspect 1. They form structures of membrane, matrix Gaucher’s Disease of cell wall, myelin sheath, microsomes and mitochondria. This disease occurs due to the deficiency of 2. They help in transport of cholesterol. enzyme β–glucosidase. Normally this enzyme 3. They help in formation of lipoproteins. hydrolyzes glucocerebrosides to form 4. They play a role in synthesis of compounds ceramide and glucose. In the absence of the called eicosanoids including prostaglan- enzyme glucocerebroside cannot be converted dins, leukotrienes. to ceramide due to which tissue gluco-  Chemistry of Lipids 25 cerebroside levels increase. Clinical features Apolipoproteins are divided by structure include hepatomegaly, splenomegaly, pig- and function into classes A to H, with most mentation of skin, etc. classes having subclasses, for example apo- A1 and apo- CII. Gangliosides They are present in greater concentration in Functions of Lipoproteins gray matter of brain. They comprise of a 1. They act as transport vehicles for lipids in molecule of fatty acid, an amino alcohol the lipid plasma. sphingosine, a sugar usually galactose or 2. They deliver the blood components glucose, one molecule of N–acetyl galacto- (cholesterol, triacylglycerol etc.) to various samine and upto three molecules of N-acetyl tissues for utilization. neuraminic acid (NANA or sialic acid). Types of gangliosides are GM1, GM2, GM3 DERIVED LIPIDS and GD3. Fatty Acids Sulpholipids Fatty acids are obtained by hydrolysis of fats. Lipids possessing sulphate groups are called A fatty acid consists of a hydrocarbon chain sulpholipids. These are largely found in white with a terminal carboxyl group. They are matter of brain and to a less extent in liver, divided into saturated and unsaturated fatty kidney, salivary gland, testis etc. acids. Saturated fatty acids are those which do Lipoproteins not contain any double bond in their structure. General formula for saturated fatty Lipoproteins are complexes of lipids and acids is CnH2n+1. Examples of saturated fatty proteins. The lipid part consists of fats, acids include acetic acid, propionic acid, phospholipids, cholesterol and its ester and butyric acid, capric acid, palmitic acid, stearic free fatty acids. These are found in cell acid, etc. membranes, milk, egg yolk etc. These are molecular complexes of lipids and specific proteins called apolipoproteins. These are in constant state of synthesis, degradation and removal from the plasma. The lipoprotein particles include: chylo- microns, very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL). Unsaturated fatty acids are those which Apolipoproteins associated with lipo- contain one or more double bonds in its proteins serve as structural components of the structure. General formula for unsaturated particles, provide recognition sites for cell fatty acids is: surface receptors and serve as activators or CnH2n-1COOH coenzymes for enzymes involved in lipo- They can be monosaturated or polyun- protein metabolism. saturated. 26 Medical Biochemistry for Physiotherapy Students Monounsaturated fatty acids (MUFA) are sources. Linoleic is the most important those fatty acids which contain one double because it is the precursor from which the bond in its structure, e.g. oleic acid and other two essential fatty acids (linolenic acid palmitoleic acid. These monounsaturated and arachidonic acid) can be synthesized in fatty acids are present in nearly all fats. the body. Biologically, arachidonic acid is the most important because it is the precursor from which eicosanoids like prostaglandins and leukotrienes are formed. Properties Polyunsaturated fatty acids (PUFA) are those fatty acids which contain more than one 1. Saturated fatty acids are relatively resistant to oxidation outside the body double bond in its structure. Examples include whereas unsaturated fatty acids are linoleic acid, linolenic acid, arachidonic acid. slowly but spontaneously oxidized in the Sources and structure is given below: presence of air leading to rancidification. Name of Structure Sources 2. In general, increasing the chain length fatty acid increases the melting temperature of a fatty Linoleic acid 18:2(9,12) Corn, peanut, acid but addition of a double bond cottonseed, decreases the melting temperature. soyabean oil Linolenic acid 18:3(9,12,15) Found frequently Therefore, the presence in membrane with linoleic acid lipids of fatty acids that contain double but particularly in bonds helps maintain the fluid nature of linseed oil those lipids Arachidonic acid 20:4(5,8,11,14) Found in small quantities with linoleic and Functions of Essential Fatty Acids linolenic acids but They are required for: particularly in Peanut oil. 1. membrane structure and function. 2. transport of cholesterol. PUFA are also known as essential fatty 3. formation of lipoproteins. acids because they cannot be synthesized in 4. prevention of fatty liver. the body and have to be provided from natural 5. synthesis of eicosanoids.  Chemistry of Lipids 27 The common names and structures of some group at C-3 is classified as sterols. Choles- fatty acids are given below: terol is the major sterol in the body. The structure of cholesterol consists of four Common name Structure fused rings A,B,C and D with the carbons Formic acid 1 numbered in sequence and an eight mem- Acetic acid 2:0 bered, branched hydrocarbon chain attached Propionic acid 3:0 Butyric acid 4:0 to the D ring. This structure is known as Capric acid 10:0 cyclopentanoperhydrophenanthrene nucleus. Palmitic acid 16:0 Its molecular formula is C27H45OH. Palmitolic acid 16:1(9) Stearic acid 18:0 Oleic acid 18:1(9) Linoleic acid 18:2(9,12) Liolenic acid 18:3(9,12,15) Arachidonic acid 20:4(5,8,11,14) Lignoceric acid 24:0 Nervonic acid 24:1(15) The numbers in the table indicate the number of carbons in the chain and the number and position of double bonds. For Cholesterol has 27 carbon atoms, a example, acetic acid, 2:0 indicates it has 2 hydroxyl group, a double bond, 2 methyl carbon atoms and no double bond i.e. it is groups and a side chain at C-17. Cholesterol saturated fatty acid. Similarly, arachidonic is synthesized by virtually all tissues but liver, acid, 20:4 (5,8,11,15) indicates it has 20 carbon intestine, adrenal cortex and gonads make the long chain and 4 double bonds which are largest contributions. Cholesterol is a between carbons 5-6, 8-9, 11-12 and 14-15. component of all cell membranes and is a precursor of bile acids, steroid hormones and Alcohols vitamin D. Cholesterol is found in largest amounts in Alcohols found in lipid molecules include normal human adults as: glycerol, cholesterol and higher alcohols like Brain and nervous tissue- 2% cetyl alcohol usually found in waxes. The Liver – 0.3% unsaturated alcohols are important pigments. Skin – 0.3% Phytyl alcohol is a constituent of chlorophyll Adrenal cortex – 10% or more. and lycophyll, which is a polyunsaturated alcohol and occurs in tomatoes as a purple Cholesterol occurs in two forms in the pigment. body i.e. free form and ester form. In ester form, it is esterified with fatty acids at –OH Steroids and Sterols at C-3 position. In brain and nervous tissue, free form predominates, while in adrenal Steroids are often found in association with cortex, it occurs mainly in esterified form. fat. Steroids with 8- 10 carbon atoms in the Much of the plasma cholesterol is in esterified side chain at C-17 and an alcohol hydroxyl form.  Chapter 5 Chemistry of Amino Acids and Proteins CHEMISTRY OF AMINO ACIDS carboxylic acid moiety attached to the same α- carbon atom. Amino acids contain the carboxyl group At physiologic pH, (approx. pH, 7.4), the (COOH), an amino group (NH2) and a side carboxyl group is dissociated; forming the chain (R group) bonded to the α- carbon atom. negatively charged carboxylate ion (COO–) Alpha-amino acids have both an amino and a and the amino group is protonated (NH3+). Although about 300 amino acids occur in nature, less than one-tenth of these occur in proteins. Complete acid-, base- or enzyme catalyzed hydrolysis of proteins produces the 20 L-amino acids. Proteins from all forms of life- plant, animal or microbial contain the same 20 amino acids. Classification of Amino Acids Amino acids are classified on the basis of acidic, basic or neutral groups as follows: They are basically of three main types: 1. Neutral amino acids 2. Acidic amino acids 3. Basic amino acids Neutral Amino Acids