Nutrition and Disorders
Nutrition
The substance used for nutrition are called nutrients. Nutreology is the study of food and their use in diet and therapy.
Types of nutrition
(1) Autotrophic / Holophytic : The individuals, which synthesizes their own food. It can be grouped into two following categories –
(i) Photoautotrophs : The individual, which synthesizes their own food from CO2 and H2O in presence of sunlight. Examples – Green plants, euglena, green sulphur bacteria, chlorobium.
(ii) Chemoautotrophs : The individuals which synthesizes their food with the help of chemical. Examples – Sulphur bacteria, nitrite bacteria, nitrate bacteria, nitrosomonas, nitrifying bacteria– nitrosomonas, nitrobacter etc.
(2) Heterotrophic : The animals derive organic food materials by consuming bodies or products of other living or dead plants or animals. Heterotrophs are of following three types on the basis of their mode of feeding.
(i) Holotrophic or Holozoic : These individuals ingest mostly solid food. Example – Animals.
(ii) Saprotrophic or Saprobiotic : They feed on dead organic matter. They absorb food through their body surface, organic fluids formed due to putrefaction of dead organism. Example – Bacteria, fungi, some protozoans etc.
(iii) Parasitic : These individuals derive their food from the body of their host. These may live inside or upon the bodies of their hosts, or may only periodically visit them for feeding. e.g., Ectoparasites (Lice) and endoparasites (Ascaris, Taenia solium).
(3) Myxotrophic nutrition : They carry out autotrophic as well as heterotrophic nutrition. Example – Euglena.
Modes of animal nutrition
On the basis of food, holozoic or holotrophic or ingestive nutritionally animals are classified into following –
(1) Herbivorous : The animal which exclusively feeds on plants. Their length of alimentary canal is more as compared to others. Examples – Tadpole larva of frog, rabbit, cow, horse, sheep etc.
(2) Carnivorous : The animal which kills and feeds on other animals. The length of their alimentary canal is minimum. Examples – Tiger, lion etc.
(3) Omnivorous : The animal which can take both plant and animal product as food. They have maximum type of digestive enzymes. Example – Human, Dog, Prawn.
(4) Insectivorous : The animal which feeds on insects. Example – Frog, Common bats, wall lizards.
(5) Sanguivorous : The animal which feeds on blood of other animal. Examples – Leech, body louse, mosquito, vampire bat etc.
(6) Carrion Eaters (scavengers) : They feeds on dead animals also termed as scavengers. Examples – Hyaena, neltura, kites etc.
(7) Cannibalus : Organisms which feeds on its own species. Examples – Cockroaches, some fishes, frog, snakes etc.
(8) Detritus : Animals feed chiefly upon organic matters present in the humus. Examples – Earthworm.
(9) Coprophagus or pseudorumination or refection : Animals which feeds on their own faeces. Example – Rabbit, Guinea pig
(10) Larvivorous : Feeds on larva. Example – Gambusia (mosquito fish) and Dragon fly.
(11) Frugivorous : Feeding on fruits. Example – Parrot, Bat, Squirrel.
(12) Food robbers : Feed upon food formed in alimentary canal. Example – Ascaris, Taenia solium.
(13) Filter feeder : Paramecium, Unio, Sponge.
Feeding mechanism
(1) Feeding mechanism in liquid feeders (fluid feeders) are as follows –
(i) Diffusion : Many parasitic organisms (protozoans, tapeworm) absorb the dissolved organic food through general body surface.
(ii) Pinocytosis (cell drinking) : Ingestion of liquid food by invagination through surface of body. Pinocytosis channels are formed at body surface to enclose the fluid food from surrounding medium. Lower ends of channels are pinched off as pinocytic vesicle or pinosomes.
(iii) Blood sucking : Their mouthparts are modified for sucking blood. Examples – Vampire bat, mosquito etc.
(2) Feeding mechanism in microphagus animals (filter feeders) : The food of such animals (paramecium, sponges, corals, bivalves, tadpole etc.) is suspended in water fluid and they have filtering devices (clusters of pseudopodia, cilia, flagella, sheets of mucous etc.) or feeding on small microscopic animals like – Amoeba, Paramecium etc.
Nutritional requirements
(1) Food : All living organism needs food, animal are unable to synthesize their own food hence they obtain it from outside sources. Animals require food for three main purposes, such as food as a fuel which provides energy and material for body maintenance, food for movement of body includes muscles contraction etc., food for growth as well as for the synthesis of body substances.
(2) Components of food : These are following types –
(i) Carbohydrates : They are made up of C : H : O, having H and O in the ratio of 2 : 1 and the general formula is (CH2O)n. They are the chief source of energy. The source of carbohydrates in our food is cereals and pulses.
Specific features
(1) Storage amount : 900 gm approx.
(2) Storage site : Chiefly liver and muscles.
(3) Daily requirement : 500 gm approx.
(4) Source : Chiefly cereals (rice, wheat, maize), pulses, potato, fruits, sugarcane, milk, honey, sugar etc.
(5) Caloric value : 4.1 k cal./gm
(6) Physiological value : 4.0 k cal./gm
Functions of carbohydrates
(1) Carbohydrates, especially glucose, are the main respiratory fuels.
(2) Ribose and deoxyribose sugars are components of nucleic acids (DNA and RNA). Galactose is a structural component of medullary sheath.
(3) Monosugars act as monomers for the formation of disaccharides and polysaccharides.
(4) Starch and glycogen, serve as reserve fuel.
(5) Excess of glucose may also be changed into fats (lipogenesis) and stored in liver, adipose tissue and mesenteries.
(6) Glucose has antiketogenic role as it prevents the incomplete oxidation of fats and formation of ketonic bodies in the blood.
(7) Glucose spares the amino acids for protein synthesis.
(8) Sucrose is the major form in which sugar is transported in the plant body. Sucrose is storage sugar of sugarcane and sugar beet.
(9) Cellulose, hemicellulose etc. are the main components of cell wall of plants.
(10) Chitin is main component of cell wall of fungi and exoskeleton of crustaceans.
(11) Heparin prevents the blood clotting inside the blood vessels (Anticoagulants).
(12) Glycoproteins form a protective layer, glycocalyx, on intestinal cells.
(13) Hyaluronic acid acts as a lubricating fluid in the synovial joints between the limb bones.
(14) Blood antigens like A, B and Rh-factor are glycoproteinaceous and provide immunity to the individual.
(15) Sugars are also important components of some glycoproteinaceous hormones like FSH (Follicular stimulating hormone), LH (Luteinizing hormone) etc. FSH controls gametogenesis while LH controls the ovulation and formation of corpus luteum.
(16) Carbohydrates may be changed into amino acids.
(17) Oligosaccharides of cell membrane help in cellular recognition.
(18) Cellulose forms roughage of food which stimulates the secretion of digestive juices. It also helps in peristalsis.
(19) Cellulose nitrate is used in explosives.
(20) Carboxy-methyl cellulose is used in cosmetics and medicines.
(21) Cellulose acetate is used in preparing cellulose plastics, shatter-proof glass, fabrics etc.
(ii) Lipids and fats : Fats and all fat like substances are called lipids. They are composed of C, H and O. They are insoluble in water but soluble in ether, alcohol, chloroform etc.
Specific features
(1) Source : Butter, ghee, liver oil, vegetable cooking oil etc.
(2) Daily requirement : 50 gm.
(3) Storage site : Subcutaneous fat, adipose cells.
(4) Caloric value : 9.45 k cal/gm.
(5) Actual value : 9.0 k cal/gm.
Functions of lipids
(1) The fats acts as concentrated fuel. The caloric fuel value of 1 gm of fats is 9.45 kcal, while the physiological fuel value of 1 gm of fats is 9.0 kcal (37 kJ), which is about 2.25 times more than the energy provided by same amount of glucose.
(2) The fats are also highly suitable for storage as the reserve food material. It is mainly stored in the liver, beneath the skin, in the brown deposits and in the fat bodies. Normally, the fats constitute about 4% of liver by weight.
(3) Fats stored in the subcutaneous tissue insulate the body against the loss of heat energy, so conserve the body heat. Thus, fats help in homeothermy.
(4) Medullary sheath is formed of white fatty substance, myelin, which insulates the nerve fibres and prevents the loss of energy.
(5) Fats from the protective shock absorbing cushions around a number of organs like the eye balls, kidneys (renal fat), ovaries, etc.
(6) These help in the absorption of fat-soluble vitamins like A, D, E and K.
(iii) Proteins : They are composed of C. H. O. N and some of in addition contain S and P. They are complex, versatile, macromolecules with very high molecular weight. Their unit is amino acids. Out of the 20 amino acids, required in human to build proteins, half of them are essential and rest are non-essential amino acid. Essential amino acids are those, not synthesized by human body and are present in food. The non-essential amino acids are those which can be synthesized by human body.
Arginine and histidine are considered semi indispensable amino acids. These two are not essential in the adult organisms.
Classification of proteins : They are following types –
(1) On the basis of structure of molecules
(i) Fibrous : Examples – Collagen, myosin, keratin, fibrin of coagulated blood etc.
(ii) Globular : Examples – Albumin, globulin, haemoglobin, enzymes, snake venom etc.
(2) On the basis of their chemical nature : The proteins are divided into three categories –
(i) Simple proteins : These are formed of peptide chains and yield only amino acids on hydrolysis. On the basis of shape, these may be fibrous proteins e.g. collagen of white fibres, elastin of yellow fibres, keratin of exoskeletal structures like nails, horns, hoofs, hair, feather etc. globular proteins e.g. albumins and globulin of blood plasma, protamines, histones, glutelins etc.
(ii) Conjugated proteins : These are formed of a proteinaceous and a non-proteinaceous prosthetic group. These include nucleoproteins (of chromosomes-DNA and proteins and ribosomes-RNA and proteins), glycoproteins (of blood-antigens), phosphoproteins (casein of milk), lipoproteins (lipovitellin of egg-yolk), chromoproteins (haemoglobin of RBCs), haemocyanin, rhodopsin (visual purple), iodopsin (visual violet), cytochromes), metalloproteins (carbonic anhydrase enzyme with Zn2+) etc.
(iii) Derived proteins : These are formed by the partial hydrolysis of simple proteins and include peptones, proteoses etc.
Specific features
(1) Source : Chief source is pulses, egg, milk, meat, fish, leafy vegetables, soyabean, groundnut etc.
(2) Daily requirement : 70-100 gm.
(3) Caloric value : 5.6 k cal/gm.
(4) Physiological caloric value : 4 k cal/gm.
(iv) Nucleic acids : These are compounds of carbon, hydrogen, oxygen, nitrogen and phosphorus. These occur in all body cells and transmit coded informations of all morphological and functional hereditary characteristics from one generation to the next. The molecules of nucleic acids are long-chain polymers of nucleotide monomers. These megamolecules are called polynucleotides. These are the largest and most complex molecules of nature.
Nucleic acids are of two types – Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Only nine types of nucleotide monomers occur in cells only four of these link by “phosphodiester bonds” forming polynucleotide chains (megamolecules) of DNA and another four of RNA. Each nucleotide is itself a complex molecule formed by linking of a nitrogenous base, a pentose sugar and a phosphate group. “Phosphodiester bonds” are also dehydration or condensation linkages. Hence, in digestion, nucleic acids of food are hydrolysed first into nucleotides. Then the nucleotide molecules are further degraded to their component nitrogenous bases, pentose sugars and phosphate groups.
(v) Water : Water is an essential constituent of protoplasm, which forms the physical basis of life, though it does not yield any energy. The water is an inorganic compound, composed of hydrogen and oxygen in the ratio of 2 : 1. Protoplasm has nearly about 70-90% water, but the human body has approximately 60�% of water.
Specific features
(1) Sources : Metabolic water, liquid food and drinking water.
(2) Daily requirement : 5- 6 glasses (4-5 litre).
Functions
(1) Water act as a best solvent.
(2) Involve in so many metabolic process.
(3) Act as temperature stabilizer.
(4) Remove excess of body heat through sweating.
(5) It also act as dispersion medium ioniser, diffusion medium.
(vi) Vitamins
Historical review
N. I. Lunin (1881) discovered vitamins. The term ‘vitamin’ was first used by Funk in 1912. Hopkins and Funk (1912) propounded a ‘vitamin theory’.
Definition : Vitamin are complex organic compounds needed daily in minute quantities and act as growth and metabolic regulatory substances.
Sources : Vitamins can only be synthesized by green plants, hence animals depend for their vitamin requirement upon the plants. Human body manufactures vitamin D using ultraviolet rays of sunlight and can store A, D, E, K and B12. The chemical compositions of vitamins are known and it is possible to synthesize them.
Importance : The vitamins are not a sources of energy. They regulate the various metabolic processes. They mostly act as the constituents of coenzymes in the cells.
Types : Vitamins are divided into two groups –
(a) Fat soluble vitamin : A, D, E and K.
(b) Water soluble vitamin : B complex and C.
(vii) Mineral elements : They forms approximately 4% of body weight. They are essential to regulate the various metabolic activities of the animals. The various types of mineral are group into two categories as minor element. Examples – Ca, S, P, Na etc. and trace element examples – Cu, Zn, Mn etc. Some of these minerals are described as follows –
Nutritional imbalances and disorders
ꂺlanced diet : The diet which contain the various nutrients in such proportions as can satisfy all the various needs of our body, is called a �lanced diet”. The proportion of carbohydrates, proteins and fats into fulfill energy requirement is 4 : 1 : 1 i.e. 65% of energy is obtained from carbohydrates and 10�% each from proteins and fats. This amount of energy is fulfilled by intake of 400� gm of carbohydrates, 80� gm of proteins and 50� gm of fats. The balanced diet must also contain sufficient amount of minerals and vitamins.
Metabolic rates
(1) Basal metabolic rate : Amount of energy required daily by a person to maintain its basal metabolism and is about 1600 k cal/day.
(2) Routine metabolic rate : Amount of energy required daily by a person to do his routine work. It is about 2800 k cal/day for males and 2300 k cal for female.
(3) Active metabolic rate : Amount of energy required daily by a person to maintain its high metabolic rate during heavy physical work and is about 4000 to 6000 k cal/day for males and 4500 k cal for females. It has been scientifically determined that a child of 4𠄶 years approximately requires 1500, a child of 13� years requires 2500 and a youth of 16� year requires 3000 k cal of energy per day.
Nutritional disorders : Every organism requires an adequate supply of nutrients in proper proportion in their diet for proper growth and development. There are two types of nutritional disorders
(1) Diseases due to over nutrition
(i) Fluorosis : Caused due to excess of fluorides. It results in tooth and bone decay.
(ii) Obesity : This is over–nutritional disorder. It is caused when 𠇎nergy inputs exceeds energy output”. It results in deposition of excess fat in the body.
(iii) Constipation : Slow movement of faeces down the large intestine causes accumulation of dry and hard stool is colon. It is generally caused by irregular bowel habits.
(iv) Diarrhoea : Rapid movement of faecal matter down the large intestine causes loose stools called diarrhoea. It may be also caused by viral or bacterial infections of intestinal tract, particularly of large intestine and by nervous tension.
(v) Piles or haemmorhoids : Enlargement of the anal veins. It may be either hereditary or may be caused due to rapid changes in the diet.
(vi) Hypercholesterolemia : Caused due to excess of saturated fats like butter, ghee, hydrogenated vegetable oils and eggs etc. It results in increased level of cholesterol in blood, arteriosclerosis, coronary thrombosis, heart attack etc.
(vii) Hypervitaminosis A : It results in loss of appetite, body hairs, painful swelling etc.
(viii) Hypervitaminosis D : It results in deposition of calcium ion in the soft tissues of the body.
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