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NUTRITION IN ANIMALS USES OF FOOD Food is needed for various life activities. The food eaten may be used by the body for the following activities. It provides raw material for growth and development It is needed to yield energy during respiration for various activities like movement, thinking, breathing, pumping of heart It may be needed to enable the body to use the raw materials and to produce energy effectively. FOOD It can be defined as any solid or liquid substance which, when taken by the body, provides it with the necessary materials to enable it to grow, to replace worn out and damaged parts, and to function normally. NUTRIENTS The molecules in the food used by the body to function properly or stay healthy are called nutrients Nutrition The study of nutrients and their relationships with food and living things is called nutrition. Diet Diets means a food that a person eats every day Balanced diet Diet that provides the correct amount of nutrients for the needs of an individual. Malnutrition Malnutrition means an incorrect or unbalanced intake of nutrients. It may be under nutrition or over nutrition. Under nutrition An insufficient total intake of nutrients is termed as under nutrition. COMPONENTS OF FOOD The food contains following important components. Proteins Fats Carbohydrates Vitamins Minerals Dietary fibers Water Carbohydrates Carbohydrates are compounds of “C, H, and O”. Their general formula is CnH2nOn. They are called hydrated carbons as the proportion of hydrogen and oxygen in the carbohydrates is same as that of water. Sources The principle sources of carbohydrates are the process of photosynthesis in green plants. It combines atmospheric carbondioxide and water from the soil in their green parts to make glucose. In this process the light energy is converted to chemical energy. The glucose synthesized is used for its own metabolic activities, any left glucose is converted 2 to starch and is stored in various parts of the plants i.e., grains, fruits, stem, roots or leaves. Some principle sources of carbohydrates include Cereals e.g. wheat, rice, oat barley Fruits e.g. banana, apple, mangoes Vegetable e.g. cauliflower, turnip etc. Classification of carbohydrates Principally carbohydrates are of three kinds, i.e. monosaccarides, oligosaccharides and polysaccharide Monosaccharides These are simple sugars. They are the basic units that built the other carbohydrates. They are soluble in water and sweet in taste. They cannot be hydrolysed into further simple sugars. Some common monosaccharides Fructose It is also called fruit sugar. It is found in fruits, plant juices and honey. The chemical formula for fructose is same as that for glucose i.e. C6H12O6. Glucose It is also called as grape sugar. It is found in ripe fruits and some vegetables e.g. onions, beetroot. It is the product of digestion of carbohydrates in the body and taken up into the blood to be supplied to the respiring cells and tissues. It is a six-carbon sugar. The glucose units may be condensed together to form various complex carbohydrates like, starch, cellulose and glycogen. Galactose It is another simple sugar that makes part of milk sugar, i.e. lactose. Disaccharides Disaccharides consist of two simple sugars joined together. Two monosaccharides usually hexoses are linked together by a glycosidic linkage. They are linked together by a process known as condensation. Condensation Hydrolysis Disaccharides are soluble in water and lesser sweet than monosaccharides. Some examples of disaccharides are Sucrose Glucose + fructose --------- sucrose Lactose Glucose + galactose -------- lactose Maltose Glucose + glucose ========= Maltose Polysaccharides These are formed from a varying number of monosaccharides units. The repeated glycosidic bonding between many simple sugar units make polysaccharides. They are usually insoluble in cold water and are tasteless. They function chiefly as food and energy stores and as structural materials. They are convenient storage molecule for several reasons. O-Level Biology Zaffar Sulehri 3 Their larger size makes them more or less insoluble in water, so they do not exert osmotic or chemical influence in the cell. Due to longer chains of simple sugar units joined together, they can fold into compact shapes. They can easily be hydrolysed to simple sugars, when required. Starch Starch is formed from many glucose units joined together by glycosidic linkages. It is a major fuel store in the plants, but is absent in animals. It can be seen in a plant cell under an ordinary microscope in the form of starch granules. And can be confirmed with iodine test, where it gives blue-black color with iodine. During digestion that starts in the mouth, starch is broken down to maltose and then into glucose in the intestine, which is absorbed into blood. Cellulose Cellulose is formed by plants from glucose units joined together in such a way that a strong, structural material is produced. It is the most abundant organic compound present on the earth. It is potentially source of glucose but naturally cannot be digested in the human body. However some herbivores have cellulase-producing bacteria in their intestines and can digest cellulose. FATS Fats are compounds of fatty acids and glycerols. They are insoluble in water and soluble in organic solvents like either, chloroform and benzene. They consist of C, H and O (Carbon, Hydrogen and Oxygen). 3(Fatty acids) + 1(glycerol) ------- 1 Fat Fatty acids Fatty acids are hydrocarbon chains with an acidic group at one end (-OOH). Most of the naturally occurring fatty acids have an even number of carbon atoms that varies between 14 and 22. They are of two kinds. Unsaturated fatty acids Saturated fatty acids Unsaturated fatty acids Hydrocarbon chain of the unsaturated fatty acids contains one or more double bonds. They are present in oils. They are liquid at room temperature. E.g. Oleic acid, a chief constituent of Olive oil. Saturated fatty acids Fatty acids and fats lacking double bonds are called saturated. Saturated fatty acids are usually solid at room temperature and are found in fats. Palmitic acid for example is a saturated fatty acid, solid at room temperature. Alcohols The most common alcohol in fats is glycerol. The formula for glycerol is given below. O-Level Biology Zaffar Sulehri 4 Formation of fats As in the above formula, glycerol has three hydroxyl groups (-OH). These hydroxyl groups under go condensation reactions with three fatty acids as shown below. Functions of fats Fats are an efficient source and storage of energy. It provides double of the energy produced from the same amount of carbohydrates and proteins. It acts as an insulating layer under the skin. It prevents excessive heat loss from the body. They are source of fat soluble vitamins like vitamin A, Vit.K, Vit.E and Vit.D They are an important compound of cell membranes. Surrounds and protects certain vital organs, e.g. kidneys Provide texture and flavour in food and help to make it palatable Foods containing fats provide feeling of fullness (satiety) after a meal, as fat digestion is slow. It helps to reduce water loss from the skin. The oily secretions from the sebaceous glands spread on the surface of skin from water loss. PROTEINS Proteins are compounds of C, H, O and N. sulpher and phosphorous may also be present in some. Proteins are made up of smaller, basic units called amino acids. Amino acids Amino acids consist of an amino group (-NH2) and an acid group (_OOH) attached with the centra l ∞- carbon. The central carbon also bears a side chain of hydrocarbons denoted by R. different amino acids have differences in this R group attached. The general formula for amino acids is given below. There are at least 22 amino acids known, naturally occurring in plant and animal proteins. Some of them cannot be synthesized in the human body, and should be taken in diet, so they are called essential amino acids. Proteins containing these essential amino acids may be called first class proteins, high biological value or complete proteins. Meat, cheese, fish, milk and eggs provide first class proteins. Proteins that lack one or more essential amino acids are called second class or low biological value proteins. The followings proteins provide low biological value proteins. Cereals e.g. wheat, rice, oats Pulses, e.g. peas, beans, lentils Amino acids are linked together by peptide bonds. A peptide bond is a linkage between nitrogen of amino group of one amino acid and carbon of carboxylic group of another amino acid. This process of linking of two or more amino acids in a chain is called condensation. O-Level Biology Zaffar Sulehri 5 Functions of proteins Our bodies are made up of millions of cells, which are constantly being replaced and require. New protoplasm is essential for the formation of new cells. So new protoplasm must be produced. The proteins are needed for The synthesis of protoplasm, i.e. for growth and repair of worn-out body cells. The synthesis of enzymes and some hormones. The formation of antibodies to combat diseases. Energy producing. Some examples of proteins and their functions PROTEIN FUNCTION Hemoglobin transport of oxygen Keratinformation of nails and hairs Myosin formation of muscles Collagen formation of bones and cartilage Insulin VITAMINS Vitamins are group of chemical substances required in small amounts. They are required to regulate the maintenance and growth of the body, and to control metabolic reactions in cells. Vitamins cannot be synthesized in human body so they should be taken in diet. Lack of vitamins causes deficiency diseases. Some common characteristics of vitamin are as follows. They are not used as a source of energy. They do not make part of body structure. They are essential for normal health and are needed in small amounts. They usually work in association with enzymes. At least fifteen different vitamins have been identified and can be classified into two groups according to the substances in which they dissolve. Fat soluble vitamins; A, B, E and K. Water soluble vitamins; vitamin C and the vitamin B-complex. Vitamin A (Retinol) Functions It is required to make a substance called visual purple, which is formed in the retina of the eye to enable it to see in dim light. For the normal development of the epithelial tissue and the mucus membranes in the throat and the digestive, bronchial and excretory system, Vitamin A is needed. It also helps in the maintenance and development of skin. Children need it in sufficient amounts for their normal growth, particularly the bone and teeth formation. Sources Animal sources Being fat soluble it is found in fatty foods or products i.e. milk, cheese, eggs O-Level Biology Zaffar Sulehri 6 (yolk), butter oily fish e.g. herring, sardine, Liver, kidneys, and cod liver oil. Plant sources In plant foods it is present in the form of carotene that may be later converted into retinal in the human body. The plant foods like carrots, spinach, watercress, apricot, parsley, cabbage, tomatoes and plumes. Dietary guide for Vit.A As vitamin A is fat soluble, it is stored in the body. So it is not necessary to be taken in the daily diet. The excess of vitamin A in the body may be poisonous. It seriously affects the development of skin and joints. In the growing ages it is very essential to be taken in the proper amounts. In the pregnant women if they eat liver for vit. A supplies, it may seriously affect the developing babies. So they should avoid liver, instead they should eat sufficient fruits and vegetable that provide carotene. It does not lead to damage and defects in unborn babies. The people with their gall bladder removed are advised not to take fats in their diet. They lack vit. A in their diets. The others, who cannot adjust fats, should be given vit. A through injections. Deficiency of vitamin A Deficiency of vit. A leads to night blindness. In sever cases it causes total blindness. The skin and mucus membranes become dry and infected, and resistance to diseases is reduced. Growth of children is retarded. Vitamin C (Ascorbic acid) Functions It helps in the formation of connective tissue. It also assists the absorption of mineral iron from the small intestine after digestion. It is needed for the development of bones and teeth. Sources Vitamin C is a water soluble substance. It is mainly found in fresh fruits and vegetables, which include blackcurrants, green pepper, kiwi fruits, oranges, grape fruits, lemon, strawberries, cabbage, spinach, Brussels sprout, broccoli and potatoes. Dietary guide for vitamin C Although it is a water- soluble vitamin, it is stored in the body in the liver, adrenal glands and through out the body fluids and tissues. A healthy man has up to 1.5 grams of ascorbic acid stored in this way. Only 45 mg of it are used daily. A daily supply of vitamin C is needed to keep the store ‘topped up’. Cooking oxidizes vit. C C and being water soluble it may be lost during washing and cooking foods. So the fresh food should be used to avoid lack of vit. C Deficiency of vit. C The severe deficiency of it causes scurvy. The symptoms of scurvy include Bleeding of gums Loosening of teeth Impaired wound healing Anemia Heart failure Vitamin D O-Level Biology Zaffar Sulehri 7 It is required for proper development of bones and teeth. It also regulates the absorption of calcium from the gut. Sources It is a fat soluble vitamin and is found in good supply in liver, cod-liver oil. It is also found in milk and dairy products. An important source of vitamin. D is a precursor in the skin that is converted to vit. D by U.V light when exposed to sunlight. Dietary guide for vit. D If is a fat soluble and can be stored in the body. Most people make enough vitamin D from the action of sunlight on their skin. So it is not suggested to give addition vitamin D for school going children, adolescent and adults. Usually deficiency of vitamin does not occur, however in babies in cold winters when they are packed most of the time and their skin is not exposed to sun light, and the house bound people or those, whose cover their body as part of religious custom, are likely to be deficient. Excess of Vitamin D in the diet can be dangerous. It assists absorption of more calcium into the blood, if in excess may be deposited in the lungs or kidneys. Deficiency Deficiency of vitamin D causes weakening of the bones and bowlegs in children called rickets. In elderly people softening of bones occurs. So they become liable to fractures easily. This is called osteomalacia. MINERALS Human body consists of at least 20 different elements. Some of them i.e. C, H, O, and N make larger proportion in the body and their main sources are carbohydrates, fats and proteins. Seven of these minerals are needed in only trace amounts for good health, and these are known as trace elements. They include magnesium, copper, zinc and iodine Calcium Functions It is the part of mineral component of the bones and teeth. It is needed in addition to other substances to initiate blood clotting It is needed for muscular contraction and transmission of nerve impulse It play a part in permeability of cells Sources Milk is a good source of calcium. The other sources include cheese, bread, bone of canned fish and hard water. Dietary guide for calcium Adults need about 800 mg calcium each day, children, pregnant and lactating mothers even need higher amounts of calcium. Fe (IRON) Functions Iron is needed fro the formation of RBCs. It is an important component of hemoglobin. It is also needed for the formation of hydrogen acceptor system of the cells. Source Liver, kidney, corned beef, chocolate are good sources of iron. Eggs, spinach, dried fruits whole grain cereals also provide iron. Dietary guide Adults need about 15mg per day. Its absorption into the blood depends up vitamin c. Vitamin C increases iron absorption from plant sources. So to ensure iron absorption the O-Level Biology Zaffar Sulehri 8 foods contain iron should be taken along vitamin c. in growing children pregnant and nursing mother more iron is needed. Deficiency It leads to anemia, the deficiency of hemoglobin & shortage of RBC’s in the blood due to iron deficiency causes iron deficiency anemia. Energy Energy is needed when a person is awake for the physical activities and even when a person is asleep to carry on the vital processes of the body i.e. heart beat, breathing etc. all energy needed is provided by the food, that is oxidized to release energy in the cells after it is digested absorbed and carried to the tissues. Uses of energy in the body In the human body the energy is used in various forms. The primary source o fall these forms of energy is the sun light which converted into potential energy in food by a process called photosynthesis the food after it is eaten is digested, absorbed and transparent to the cells or tissues where it is oxidized to produce energy. The energy released may be used to maintain the body temperature or to make ATP. ATP is used to perform various activities in the body. Ti is converted to mechanical energy to bring about muscular movement or may be transformed into electrical energy for the transmission of nerve impulse. Energy Sources Various kinds of foods are initially the source energy for the body. The carbohydrates in our diet are the cheapest and readily available source of energy, proteins that should be an essential part of our diet are usually expensive and produce almost the same energy as provided by carbohydrates, fats are rich source of energy, they provide double of the energy released from carbohydrates or proteins. Energy Release in the body Oxidation of food releases energy. And will be discussed separately. Measurement of energy The amount of energy that can be obtained from food is measured in calories or joules. 1 cal = m4.2 joules the other conversions of these units are 1000 cal = 1 kilo cal and 1000 joules = 1 kilo joules 1 kilo cal = 4.2 kilo joules Kilo calorie Amount of heat energy needed to raise the temperature of one kilogram of pure water by 1 degree centigrade Measurement of energy content of a food provided In the living cells the energy is released during oxidation. However combustion of food releases energy in the form of heat. The energy value of any food can be measured based on an assumption, that the energy released during combustion is equal to the energy released during oxidation. The energy value is found using a food calorimeter Procedure A weighed sample of food is completely burned in an atmosphere of oxygen. The heat released by this combustion is transferred to a known volume of water, which rises in O-Level Biology Zaffar Sulehri 9 temperature as a result; the energy value of the food can be calculated as follows Energy value of food in calories per gram = Temperature rise (0C) Energy values of different foods The energy values of the organic components of food are given below Fats 3g kj/g or 9kcal/g Protein 17 kj/g or 4cal/g Carbohydrates 16 kg/g or 3.75 kcal/g Vitamins and dietary fibers are organic components of food but they do not release energy in the body. Energy requirement It requirements of an individual vary from that of the others. The factors that effect the energy requirement are explained below. Climate People living in colder regions tend to lose more heat to the atmosphere so they need more energy in order to maintain their body temperature. To conserve heat loss thick insulating layer of fats may be deposited under the skin Body size In similar climatic condition, the people of the same sex and age may have different body sizes and weights. Age Young children require more energy for their size than adults as they are growing rapidly and tend to be very active most of the time. With the increase in age the energy requirement decrease due to the slowing down of the body metabolism and reduced physical activity. Sex Men have bigger built than the women of the same age, the metabolism is higher in men so they need more energy Occupation and physical activity The amount of energy needed depends upon the basal metabolism and physical activity. Energy needed = BM + energy needed for physical activity The physical activity in the adults may be related to their work or occupation Sedentary office workers, drivers teachers, journalist, doctors, layers, shop workers energy needed 450 kJ Moderately active: light industry and assembly plants railway workers, postmen and women, plumber’s etc. 1500kj Very active coal miners, steel workers, army recruits, labours (2050kj) Pregnancy Pregnant women need extra energy for the growth of the baby, to hold or to carry the extra burden and the adjustments of the mother’s body to pregnancy. Balanced diet A balanced diet contains the right proportion of carbohydrates, protein, fats, vitamins, minerals, water and roughage to meet the daily requirements of the body O-Level Biology Zaffar Sulehri 10 A balanced diet varies from person to person, the proportion of the nutrients required in the diet is really affected by the life style, occupation, age, sex and state of the body of a person, and the food after it is eaten is digested and absorbed. It is oxidized to release energy and is metabolized for growth and repair of the body. As the energy requirements and growth state varies from person to person, the balanced diet for various categories may be discussed as below. Pregnancy The developing embryo in the wombs of a mother needs amino acids for building the proteins of its tissues, calcium for development of skeleton, iron for blood formation and energy to carry out all these metabolism activities, the developing embryo obtained all these substances from the blood of mother. So a pregnant woman should increase her protein, calcium and iron intake. She should also ensure various vitamins in her diet that are essential for normal development of the embryo. Lactation Milk production for feeding the baby is called lactation. Lactation means the production of breast milk for feeding the baby. The production of milk depletes protein and minerals from the mother’s body. So she should take extra amount of proteins and diet containing minerals especially calcium and iron. Age The young children require more energy for their active life and growth. So the food requirements of children in proportion to their body weight are more than adults. In the children formation of new tissues, blood and development of skeleton demands foods rich in proteins, iron and calcium. High carbohydrate food should be avoided in children. Great care should be taken, if vitamin A, D is to be given extra. Their too much amount may be poisonous however their adequate supply is very essential for normal growth in children. With the increase in age the growth rate slows down and in old age the people usually become less active. They lose their teeth and digestion becomes very slow so they take little food. It may result into lack of many essential amino acids, fatty acids and minerals and vitamins in their diet. They should be given food that can easily be chewed and digested and still provide low level of vitamins and minerals. Malnutrition Malnutrition means bad feeding. It could include Eating foods in the wrong proportions, for example very high fat content in the diet. For an adult the balanced diet on average provides almost 1200 kj of energy. Foods may be eaten more than it is needed. Eating too little food than is needed daily. Over nutrition If the diet contains more energy than needed by the body for basal metabolism and physical activities, the excess will be stored as glycogen or fat. However, body can store a limited amount of glycogen in the body and unlimited amount of fat under skin and round the vital organs. Its storage above a healthy limit causes obesity and the person is called obese. Obesity Obesity can be defined as a state of individual that has 20% more weight than the average for some one of its height and overall frame size. Causes of obesity O-Level Biology Zaffar Sulehri 11 The major factors that result into obesity are Eating more food Eating high energy food Genetic predisposition Physiological disorders Physically less active life Effects of obesity Obesity can lead to Cardiovascular diseases Diseases of the joints Diabetes Hernias Emotional problems Under nutrition Under nutrition is not a problem of most developed countries. In the developing countries like Pakistan, many people have diets, which bear neither adequate nor balanced. Their diets do not provide enough ener4gy for their metabolism and physical activity. Some people receive energy just to ‘stay alive’. Food may lack minerals, vitamins or even essential amino acids or fatty acids in their diets that result into various deficiency disease4s. Some of them are described below. Kwashiorkor The kwashiorkor literally means” the sickness the old baby gets when the new baby comes”. Causes of kwashiorkor As the meaning of kwashiorkor itself explains, its causes can be. The first child is removed from the breast milk that provides best food for the babies, and switched to starchy diet that results in protein deficiency. Signs and symptoms of this disease The child suffering from kwashiorkor show characteristic appearance. Hairs Hairs become white or red. They weaken and fall easily Moon-faced Swelling on the lower cheeks gives characteristic moon-faced appearance. Abdomen Abdomen swells and enlarges Skin The skin turns pale, scaly and rough. Lesions appear and wound healing is also reduced. Body size If the children suffering from kwashiorkor or not given proper treatment, die before the age of five. Their growth reduces and their muscles become thin. Treatment Protein rich diet, vitamin supplement and proper nursing can help to recover from kwashiorkor. O-Level Biology Zaffar Sulehri