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Introduction |
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Nutrition can be defined as the process by which an organism obtains food which is used to provide energy and materials for its life sustaining activities. |
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Carbohydrates |
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Carbohydrates are the chief energy providers of the organism. They are made up of carbon, hydrogen and oxygen. |
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Proteins |
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Proteins are the chief body builders of the body. They are complex molecules made up of carbon, hydrogen, oxygen and nitrogen (sometimes sulphur and phosphorus). Proteins are used to synthesize enzymes (e.g., pepsin, trypsin), hormones (e.g., insulin, adrenaline), carrier proteins (e.g., Haemoglobin), contractile proteins (e.g., myosin, actin), structural proteins (e.g., collagen) and protective proteins (antibodies). They also form skin pigments like melanin and nucleic acids of the genetic material, DNA and RNA - purines and pyrimidines. |
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Fats |
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Fats are the main energy storers of the body. On oxidation, fats give almost two and a half times the energy as that of glucose or glycogen. This makes it most suitable for energy storage. It, however, uses up more oxygen molecules during oxidation when compared to carbohydrates as it contains lesser oxygen. Fats are stored in adipose tissue in certain regions of the body like under the skin and between internal organs. In addition to storage, fats are also used to synthesize structural lipids such as those of membranes. |
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Vitamins |
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Vitamins are a complex group of organic compounds that are required in small quantities for regulation of various body activities. Though they are needed in small quantities, they are essential for our well being. Since most of them cannot be synthesized in the body, they must form a part of our diet. Lack of these vitamins in the diet results in deficiency disorders. |
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Minerals |
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Minerals are inorganic nutrients. They include both metallic and non-metallic elements, which are taken by the body in the form of salts. There are 24 elements that are used in our body. They have various functions such as formation of tissues such as the bone, conduction of nerve impulses, formation of RBCs, etc. There are eight major elements required by man and the others are needed in traces. The major elements are sodium, chlorine, potassium, calcium, phosphorus, sulphur and magnesium. Some of the trace elements or microelements are fluorine, zinc, copper, iodine, iron, manganese, chromium, cobalt, etc. However, they are all important for the well-being of the human body. All the minerals are basically obtained from the plants as they absorb these minerals from the soil. |
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Balanced Diet |
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The human body requires various types of nutrients in order to keep the body healthy and fit. These nutrients should be taken appropriately in our diet. The diet that we follow should be balanced. Balanced diet is a diet, which provides all the nutrients needed by the body in correct proportions. |
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Nutritional Disorders |
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Nutritional disorders occur due to malnutrition. Malnutrition refers to bad nutrition and can therefore be applied to both undernourishment and overeating. Undernourishment is a serious problem in developing countries with a large population being deprived of a balanced diet or even one full meal a day. Most affected are the children under five years. Undernourishment may be deficiency of proteins, vitamins or minerals. Deficiency of these nutrients leads to diseases, often serious and fatal. |
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Vitamin Deficiency Diseases |
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It is caused by the deficiency of vitamin A, affects the rod cells of the retina. This leads to poor adaptation of eyes to dim or night light causing night blindness. The cornea and the conjunctiva also become dry. This condition is called xerophthalmia (dry eyes). Severe deficiency results in keratomalacia in which ulcers develop on cornea, leading to blindness. |
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Mineral Salt Deficiency Diseases |
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It is caused due to the deficiency of iron. Iron is necessary for the production of haemoglobin, a protein that is an oxygen carrier in blood. When the level of haemoglobin drops in the blood it results in the person feeling tired easily, loss of appetite, loss of weight and pale appearance due to loss of oxygen in blood. This is called anaemia. It can be prevented and cured by having a diet rich in iron such as greens like spinach, liver, milk, apple, guava, etc. |
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Nutrition and Its Types |
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The term nutrition includes the way an organism obtains its food and also the processes by which the nutrients in the food are broken down to simpler molecules for the utilisation by the body. |
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Types of Heterotrophic Nutrition |
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Heterotrophic nutrition is broadly classified as holozoic, saprotrophic and parasitic. |
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Holozoic Nutrition |
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Holozoic animals are boradly classified into three categories based on their food habits. |
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Digestive System in Cockroach (Invertebrates) |
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Nutrition in cockroach is holozoic and it is an omnivore, feeding on different kinds of organic matter. It takes in pieces of food and has to grind them before digesting them. Thus its mouth parts are modified accordingly for chewing the food. |
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Structure of the Human Digestive System |
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The structure of the human digestive system is adapted to the omnivorous diet. The human digestive system consists of an alimentary canal, which is approximately 8 metres long. The alimentary canal carries out digestion, absorption and egestion. |
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Mouth Cavity |
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Mouth cavity is the anterior opening of the digestive system which ingests food. It has a muscular tongue on which are arranged the taste buds. There are two rows of teeth - upper and lower. |
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Pharynx |
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Pharynx is the portion of the alimentary canal after the mouth. It is a funnel-shaped passage common to air and food. |
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Stomach |
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The oesophagus opens into the stomach. The stomach lies on the left side of the abdomen. It is a sac-like organ, which is connected to the oesophagus at the anterior by a cardiac sphincter and to the small intestine at the posterior end by a pyloric sphincter. The stomach is an elastic organ with the wall having folds. These folds open out to accommodate more food. It serves to temporarily store the food (upto 4 hours). It has three layers of muscles, unlike the other regions of the alimentary canal, which help in the churning of food. |
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Small Intestine |
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Duodenum is a short portion of the small intestine which is looped and measures about 25 cm. |
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Large Intestine |
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Small intestine enlarges slightly to form a tubular large intestine which is 5cm wide and 2m long. |
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Digestive Glands and Their Secretions |
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It is the largest gland and is found in the upper part of the abdomen on the right side just below the diaphragm. Its secretion is called bile juice. It is alkaline and rich in organic (steroid) salts called the bile salts. The alkaline nature serves to neutralize the acidic pH of the gastric juice and creates the right environment for the intestinal enzymes to function. |
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Gall Bladder |
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It is a small sac-like elongated organ near the liver. The excess bile juice is stored in the gall bladder. It is connected to the liver by a duct called the cystic duct. If there is no food in the intestine, the bile juice flows into the gall bladder and is stored there. It is pumped out by the muscular contraction of the gall bladder wall when the food comes into the small intestine. The cystic duct opens into the common bile duct which opens into the small intestine. |
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Pancreas |
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It is a small sac-like elongated organ near the liver. The excess bile juice is stored in the gall bladder. It is connected to the liver by a duct called the cystic duct. If there is no food in the intestine, the bile juice flows into the gall bladder and is stored there. It is pumped out by the muscular contraction of the gall bladder wall when the food comes into the small intestine. The cystic duct opens into the common bile duct which opens into the small intestine. |
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Other Digestive Juices |
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It is present at the bend of the duodenum. It secretes pancreatic juice which has an almost neutral pH (6 to 7). This juice is secreted into the common bile duct and then into the duodenum. About 700cc of pancreatic juice is secreted everyday. |
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Mechanism of Digestion |
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Renin is present only in young children. It digests the milk protein, casein. Casein is hydrolysed into paracasein which gets precipitated as insoluble calcium paracaseinate. This is called coagulation. Renin secreted by the gastric mucosa of the calf is extracted to make rennet tablets used to commercially curdle milk. |
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Control of Digestion |
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The bolus is then passed into the pharynx by an involuntary swallowing action. It is made easier by the presence of mucus along the walls of the alimentary canal. |
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Hormonal Control of Digestion |
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Digestion is actually carried out by enzymes but the secretion of these enzymes is controlled by the nervous system and endocrine system. |
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Absorption |
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Digestion is also controlled by the secretion of organic substances called hormones by the endocrine glands. Each hormone has a specific target organ. The hormones reach the target organ through the blood stream. The hormones controlling digestion are secreted by the walls of the stomach and duodenum. |
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Assimilation |
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After the food is broken down into a soluble form, the intestinal walls of ileum absorb the nutrients and also water. Due to its larger surface area, thin wall lining the cavity and large number of finger-like projections, called the villi, maximum absorption takes place in this portion of the alimentary canal. The food that is absorbed passes through the epithelial cells of the villi and then into the blood capillaries in the villi. From the capillaries, the fat-soluble substances pass into the lymph. These substances are then transported throughout the body by the lymphatic system, which drains them into the blood near the heart. |
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Activities and Experiments |
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The food that is digested is absorbed into the blood and lymphatic systems. The lymphatic system carries the digested fats as fatty acids and glycerol into the blood vessel going into the heart. The digested food in the blood stream reaches the liver. Here, the excess glucose is stored as glycogen to be used in times of need. The cells take the glucose they need from the blood directly for respiration. Cholesterol is manufactured from some fatty acids. The amino acids are used to form required proteins. Excess amino acids are deaminated. This process produces ammonia as waste. This ammonia is converted into the less harmful urea. The latter is then transported through the blood stream to the kidney from where it is excreted as urine. |
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Summary |
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Boil egg white in distilled water till a cloudy suspension is obtained. Cool it and divide the mixture into five equal portions in separate test-tubes. Label them A to E. |
