HUMAN BIOLOGY AND HEALTH

ENDOCRINE GLANDS

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In the multicellular organisms, various types of glands are found that can be grouped into two types : Exocrine glands and endocrine glands.

a) Exocrine glands: the glands whose secretions are conducted through duct (duct bearing glands). These glands produce enzymes.

b) Endocrine glands: the glands which do not have ducts and whose secretions are poured directly into blood (ductless glands). Special chemical substances produced but they are termed as hormones. Endocrine glands together constitute the endocrine system.

The principal function of endocrine system is to control, co-ordinate and influence the various physiological processes and activities of the body.

Hormones: Hormones (Gr. Hormaein meaning, “to excite”) are the special chemical messengers secreted in restricted areas of body by endocrine glands. They influence the activity of various organs. They have following properties-

i. They are called the “chemical messengers” of the body.

ii. They are effective even in small quantities. Their small amount produces a marked effect.

iii. They are transported to the target organs by blood, not by duct.

iv. They are proteinaceous or steroids.

v. They cannot be stored as they are oxidized or destroyed easily.

vi. Excess or deficiency of hormones may results serious physiological disorders.

vii. They are soluble in water and blood can easily diffuse through the cell membrane.

History - first hormone secretion was discovered by the English physiologist William M. Bayliss and Ernest H. Starling in 1903. Starling coined the term hormone in 1905. Banting, isolated insulin hormone in 1920 and was awarded Novel Prize in 1923.

Functions of hormones – According to Scharrer and Scharrer (1963), hormones regulate or control the following activities-

1. Growth, maturation, and regeneration – hormones regulates growth, moulting, metamorphosis, regenerative activities, diapauses, etc.

2. Reproductive activities- hormones control gametogenesis, development and maintenance of secondary sexual characters and initiation of spawning and ovipositon.

3. Metabolism and homeostasis – these regulates the basal metabolism, maintain internal environment factors including regulation of temperature, water and ion balance, blood glucose level, etc.

4. Adaptation- Hormones make adaptations to external factors including visual adaptation to light intensities and control of physiological colour changes.

Types of hormones

Depending on their chemical structures, hormones may be of following types:

1. Proteinous or polypeptide hormones like insulin, glucagon, secretion, parathormone, oxytocni, etc.

2. Steroid hormones like androgens, oestrogens and adrenocorticiods.

3. Phenolic hormones (neither protein nor steroid) like thyroxine, adrenaline or epinephrine, etc.

4. Glycoproteinous hormones like thyrotrophic, FHS, LH etc.

Endocrine glands in human

In human endocrine glands are found in different parts of the body. These endocrine glands are:

1. Pituitary gland

2. Thyroid gland

3. Parathyroid gland

4. Pancreas

5. Adrenal gland

6. Thymus

7. Pineal gland

8. Sex gland

Pituitary (Hypothalamic) gland

It is most important endocrine gland in the body. Pituitary gland is also called “master gland” because many of its hormones control the functioning of other endocrine glands.

Location: it is found at the base of brain, specifically the diencephalon and is enclosed in a depression of the sphenoid bone of the skull. It is connected to the influndibulum by a short stalk. There is communication between the hypophysis and the pituitary gland by means of nerve fibers and complex arrangement of blood vessels which pass between them through infundibulm.

Structure: pituitary glands or hypophysis is the small endocrine gland. It is a small body about the size of large pea, weighs about 1gm. It is reddish-grey in color and roughly oval in shape.

Morphologically, pituitary glands is composed of three lobes

a) Anterior lobe,

b) Intermediate lobe (pars intermedia),

c) Posterior lobe.

Functionally, the anterior and intermediate lobes of the pituitary gland are collectively known as andenohypophysis, while posteriorlobe is known as neurohypophysis.

Hormones of adenohypophysis

Anterior lobe of the pituitary lobe secrets seven different hormones which are briefly described here:

i. Follicle-stimulating hormone (FSH) – It stimulates development and maturation of ovarian follicles to produce eggs in females and to promote spermatogesis in males.

ii. Luteinizing hormone (LH) – in females LH stimulates ovulation, formation of corpus luteum and secretions of secondary hormone called progesterone and oestrogen

MALNUTRITION

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For proper growth and development, every organism requires an adequate amount of nutrients in proper proportion in their diet. If a person takes excessive nutrition (over nutrition) or deficient nutrition (under nutrition), it causes nutritional deficiency disorders. The nutritional deficiency of a nutrient for a long period causes the structural and functional disorders of some body parts. Such disorders caused by under nourishment are called deficiency diseases.

There are two types of nutritional disorders like over nutrition and under-nutrition. The under nutrition also called malnutrition, which is characterized by nutritional deficiency which may be both quantitative and qualitative. Over-nutrition causes obesity and hypercholesterolemia.

1. Disorder due to under- nutrition: The protein nutrient deficiency in the diet causes the protein-energy malnutrition(PEM). It is characterized by dietary deficiency of proteins and total food calories. Infants and young children are especially susceptible, as they need sufficient nutrients to grow and develop normally. Malnutrition reduces the ability to combat other illness and infection. Malnutrition is most common in most part of rural areas. Two most commonly occurring diseases of infants and children due to PEM in poor families are:

· Kwashiorkor

· Marasmus

I. Kwashiorkor : This is the disease caused by continued deficiency of proteins in diet. It was first reported from Africa but now it is prevalent in many parts of the world. It is one of the most commonly found deficiency diseases which mainly occurs in children among the age of 1 to 3 years, especially belonging to poor families. Generally, a child getting less than 1 gm protein per kg body weight per day suffers from this disease.

Causes- Main causes of Kwashiorkor are:

a. Prolonged breast feeding by the mothers having in adequate proteins in their diet.

b. Diet mainly containing carbohydrates and fats.

c. Late intake of supplementary food.

Symptoms- This disease is characterized by following symptoms:

Loss of appetite and reduced vigour, poor physical and mental growth, anemia, protruded belly and bulging of eyes, repeated diarrhea, darkening of skin, atrophy of muscles and oedema of hands, feet and face, increased sensitivity to infections.

II. Marasmus: it is also most commonly in children below one year of age. It is caused due to simultaneous deficiency of proteins and total food calories due to prolonged starvation.

Causes- Main causes of marasmus are:

a. Early replacement of mother’s milk by other foods deficient in proteins and calorific value.

b. Less spacing between the children.

Symptoms- it is characterized by- Shriveled appearance of child, extreme thinning of limbs (emaciation), ribs become prominent as the fat layer below the skin disappear, retarded physical and mental growth, skin becomes dry and wrinkled, digestive disorders and repeated diarrhoea.

2. Disorders due to over- nutrition

i. Obesity – this is very common nutritional disorder in which there is accumulation of excess body fat in the body. It is caused by ingestion of greater amount of food than can be utilized by the body for energy i.e. when “energy input exceeds energy output”. Obesity causes the development of a number of diseases such as cardiovascular diseases, gallstones, osteoarthritis, diabetes, etc.

ii. Hypercholesterolemia- it is caused due to excess intake of saturated fats like butter, ghee, vegetable oils, red meat and eggs. These foods increase tremendously the level of cholesterol in blood. These cholesterol get deposited on the walls of blood vessels that may cause the development of symptoms like high blood pressure, various cardiovascular disorders, etc.

BALANCED DIET

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Proper quality and quantity of food is most significant basis of health, proper growth, normal activity, vigour and longevity. Human food should contain the various nutrients in such proportions as can satisfy all the various needs of body. Such a food is called balanced diet.

Balanced diet varies from person to person, age to age and sex to sex. A person generally obtains 4 calories of energy from 1 gram of carbohydrates and proteins, and about 9.3 calories from one gram of fat. I t has been discovered that, in our energy requirement, we obtain about 50% energy from carbohydrates, 35% from fats and 15% from proteins. Thus the daily dietary requirement of a normal man is about 400 to 500 gm of carbohydrates, 65 to 75 gm of proteins and 60 to 70 gm of fats.

Balanced diet chart

WATER

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It is a liquid compound made up of two part7s of hydrogen and one part of oxygen. It usually forms about 70% to 90% part of cytoplasm and 45% to 80% part of the whole body. It does yield energy, but it is vital in the maintenance of life.

Structure

The water molecule, H2O is formed by the combination of two hydrogen atoms and one oxygen. The molecule behaves as dipole, as oxygen atom shares two electrons with each of two hydrogen atoms. One end of water molecule is slightly positive and the other slightly negative. The electronegative oxygen atoms tend to attract the single electron of the hydrogen atom. Several water molecules tend to get attracted t each other, forming a Lattice Structure. These bonds are not strong and are called hydrogen bonds.

Biological function of water

i. i) Water act as a best solvent: it is the medium in which soluble materials are dissolved.

ii. ii) Water as a reagent: there are some reactions in the body which are ionic in nature and ionization takes place in water.

iii. iii) Water as a temperature stabilizer: it means large amount of heat can be lost with minimum loss of water. It causes elimination of excess heat by evaporation of sweat which gives a cooling effect.

iv. iv) Water as a high surface tension: Due to high surface tension and cohesion, conduction of water through xylem vessels in the plants is possible.

v. v) It is the medium of transport of some substances in the body like foods.

MINERALS

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Minerals are the elements which are present in small amounts about 4% of human body weight constitute minerals. They play important role in metabolism of body.

Categories of minerals: there about 25 types of element found in the body. On the basis of their amount required by body, these are grouped into 2 categories:

i. Macro elements: These are required in large amount (more than 1gm). These include Ca, Mg, K, Na, Cl, S & P.

ii. Micro elements: these are required only in small amounts (less than 1 gm). These are also called as trace elements. These includes Cu, Co, Cr, Zn, Se, Fe, Mn, I, F, etc.

Macro elements: Important macro elements are

a) Calcium- It is found mainly in dairy products, egg, wheat germ, and dark green vegetables. It is useful for the formation of bone and teeth. It help in blood clotting and keeps muscles and nerve activity normal. Its deficiency causes rickets and muscle spasms.

b) Magnesium- Its main sources are dairy products, cereals, green leafy vegetables, seafood, chocolate, and wheat germ. It helps in release of energy. It also acts as catalyst. It helps in muscle relaxation and keeps nerves relaxed. Its deficiency causes convulsion and hallucinations.

c) Potassium: It is found in most of fruits and vegetables, and wheat germ. It is important for normal muscle and nerve activity. It is an alkalinizing agent and hence prevents acidosis. Its deficiency causes muscle disorders including cardiac muscle and nerves.

d) Sodium- its main sources are table salt, food, and wheat germ. It works with potassium. It maintains pH balance of body fluid. It helps in muscle activity and transmission of nerve impulses. Its deficiency causes cramps, diarrhea and dehydration.

e) Chlorine- it is found in salt, seafood vegetables, and chlorinated water. It is essential for pH balance of body fluid.

f) Sulphur- its sources are meat, dairy products and eggs. It is essential for synthesis of vitamin B1 and essential for healthy for healthy hairs, skin, nails. Its deficiency may interfere with healthy growth of hair and nail.

g) Phosphorus- its sources are meat, fish, egg, dairy product and wheat germ. It is important for formation of bone, teeth, and biomembranes and it keeps muscles and nerve activity normal. It is a part of energy carriers (ATP, ADP, AMP) nucleic acids (DNA, RNA) and coenzymes (NAD, NADP, FMN, FAD). Its deficiency causes loss of bone minerals and many metabolic disorders.

Micro elements

a) Chromium- it is found in meats and animal proteins except fish, black gram, soybeans, carrots, brown nuts and tomatoes. It works with insulin in the metabolism of sugar. Its deficiency causes diabetes like problems.

b) Cobalt- it is obtain from milk, meats. It is a part of vitamin B12. It helps in erythropoesis and in the action of certain enzymes.

c) Copper- it occurs in peanuts, beet, barley, soybeans, peas etc. it promotes utilizations of iron in the hemoglobin. Its deficiency causes anemia.

d) Fluorine- it is found in fish, tea, most city water supplies. It maintains healthy teeth. Its deficiency causes weak teeth which are prone to decay.

e) Iodine- it is found in iodized salt, seafood, drinking water, and onions. Iodine is a component of thyroxin hormone of thyroid gland. Its deficiency cause goiter.

f) Iron- it is found in most meats, dried nuts, cereals, beans, honey, green leafy vegetables, etc. it is a component of hemoglobin. Its deficiency causes anemia.

g) Manganese- it is present in liver, nuts, legumes and wheat grams. It is important for normal reproduction, function of mammary glands and synthesis of hemoglobin. Its deficiency causes infertility. Spongy bones, menstrual problems and unpaired causes infertility, spongy bones menstrual problems and unpaired fat metabolism.

h) Molybdenum- it is present in wheat, black gram, peas, wheat, black grams, peas, bajra, cabbage etc. it is essential for the synthesis of hemoglobin and absorption of iron. Its deficiency causes some disturbances in iron metabolism.

i) Zinc- it is present in soybeans, black grams, wheat, groundnuts, coconut, onions, peas, almonds, milk and eggs. It’s very important mineral. It is a co factors of many enzymes such a carbonic anhydrate and alcohol dehydrogenase. It is also essential for metabolism of vitamin A and hastens healing of wounds. Its deficiency in diet causes poor growth, slow sexual development, impaired wound healing.

VITAMINS

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Vitamins are the organic compounds that always taken from outside the body along with food in small quantity. They are required in balanced amount and are very essential to metabolism of body. Their deficiency and excess both cause metabolic disorders. The earliest known vitamin is vitamin C but earliest extracted vitamin is vitamin B1.

Classification of vitamin – On the basis of solubility, vitamins are of two types-

(A) Fat soluble vitamins- They are insoluble in water but only soluble in organic solvents like chloroform or alcohol. They are oily in nature

(B) Water soluble vitamins- They are soluble in water.

(A) Fat soluble vitamins- Fat soluble vitamins are following types:

(a) Vitamin A (Retinol) or Antixeropthalmic vitamin- It is a fat soluble vitamin, exits in nature as such or in provitamin form and as carotene pigment mainly found in green pigment. This vitamin was recognized bat McCollum and Davis in1913.

This vitamin influences the growth of the body and protects from infections. Therefore, t is known as anti-infective vitamin and growth vitamin. It is also necessary for the maintenance of normal epithelial tissues of the organs including conjunctiva and cornea. Rational combines with posing protein to from rhodopsin (visual purple) of rod cells of retina. Thus it is essential for night vision.

Sources: Animal sources are fish, cod lever oil, egg yolk, butter, ghee, milk, etc. Plant sources are carotenoids (Provitamin A) found in green leafy vegetables, papaya, tomatoes, carrot, etc.

Deficiency or Avitaminosis: the deficiency of retinol causes permanent dryness of cornea of eyes called Xerophthalmia but extreme case it causes destruction of cornea called Keratomalacia. Deficiency of Vitamin A also results in the decrease of rhodopsin and thus person suffers from night blindness (Nyctalpin).

(b) Vitamin D (Calciferol) or Antirachitic Vitamin: This vitamin was also discovered by McCollum and his co-workers. Since its deficiency caused disease rickets in man, it is known as antirachitic vitamin. This vitamin plays important role in calcium phosphate metabolism. It controls the deposition of calcium and phosphorus in tissue. It is also essential for normal formation of bone and teeth.

Sources of Vitamin D: it is found in Fish liver, butter, eggs, and milk. The pro vitamin D (ergosetrol) is commonly found in plants (e.g. ergot and yeast) which are transformed into vitaminD under the influence of UV radiation in vegetables.

Deficiency of Vitamin D: Its deficiency causes rickets or rachitis in children in which proper calcification of bone does not occur. In adults, its deficiency leads to osteomalacea. It is characterized by the softening of bones specially pelvic girdles, ribs and femur leading to deformities in the body posture. (

(c) Vitamin E (Tocopherol ): This vitamin was discovered by Evans and Sure in 1922. This vitamin is also now as antisterilitic factor or beauty vitamin because it prevents sterility in females and maintains the normal health of the sex organs and ensures the normal condition.

Sources of Vitamin E: It is usually found in vegetable seed oils, corn oil and oil of wheat grains and green leafy vegetables.

Deficiency: Deficiency of vitamin E causes reversible sterility in females which is characterized by ovulation, fertilization and implantation but foetus resorbed in the uterus after sometime. In male its deficiency causes destruction of germinal epithelium of testes and thus failure to produce spermatozoa resulting sterility.

Vitamin K (Antihaemorrhagic) or Phylloquinone: This vitamin is necessary for the formation of Prothrombin in liver which participates in blood clotting. Dam 1934 discovered and named this vitamin K from the term koagulation it is available in two forms- K1 and K2. Both are the derivatives of naphthaquinone.

Sources: It is mainly available in vegetable sources like green leafy vegetables like, sunflower, spinach, etc. it is rich in animal sources like, liver, egg yolk, etc. it is also synthesized d by symbiotic bacteria of intestine (colon)

Deficiency: Deficiency of vitamin causes failure of blood clotting called hypoprothrombinaemia even after minor injuries resulting into profuse bleeding that is called haemorrhage.

VITAMINS and their characteristics

Name	Main occurrence	Effectiveness	Lack	Overdosing	Increased need	Characteristics	Daily need
Vitamin A(Retinol)	Cod-liver oil, liver, kidney, milk products, butter, yolk, as provitamine A in carrots	Normal growth, function and protection of skin, eyes and mucous membrane	Growth stop, night blindness	Impaired visions, headache, nausea, vomitus, tiredness, skin change	Smoker, vegetarian, in case of high alcohol consumption, intake of cathartic, birth control pill, antibiotics	Fat-soluble, light and oxygen-sensitively	approx. 1 - 5mg
Vitamin B1(Thiamin)	Wheat germs, wholemeal cereals, peas, heart, pork, barm, oatmeal, liver, brown rice	Important for the nerve system, liver damage, inefficiency, pregnancy, mosquito protection (high-dosed), production of energy, affects the carbohydrates metabolism, important for the thyroid function	Heavy muscle- and nerve disturbances, tiredness, dyspepsias, dropsy, cardiac insufficiency, cramps, paralyses, prickle in arms and legs	none	Diet, youth, pregnant and nursing women, alcohol consumption, intake of birth control pill, antibiotics, chemotherapye	Water-soluble, Thiamin gets destroyed by heat and long storage, but not by freezing. Daily intake of vitamin B1 is important, because the body can´t store B1, which comes over the food	approx. 2mg (At carbohydrates-packed nutrition some more)
Vitamin B2(Riboflavin)	Milk products, Meat, wholemeal cereal, cheese, eggs, liver, sea-fish, green leafy vegetables, whey powder	Important for body growth, untilization of fats, protein and carbohydrates, well for skin, eyes and nails, important energy bringer, oxygen transport	(rarely) skin inflammation, brittle nails, anaemia, callus attrition	not known	Pregnancy, intake of birth control pill and antibiotics, chemotherapy, fever, smoker, old people	Water-soluble, food with Vitamin B2 should be stored cool and dark.	approx. 2 mg
Name	Main occurrence	Effectiveness	Lack	Overdosing	Increased need	Characteristics	Daily need
Vitamin B3(Niacin, Nicotine acid)	Barm, peanuts, peas, liver, poultry, fish, lean meat	Building and degradation of fat, protein and carbohydrates, good sleep	Skin and mucosa inflammation, headache, trembling, vertigo, sleep disturbance, depressions, feeling of prickle and deafness in the limbs	(with over 100mg a day) pruritus, nausea, allergies	Labor, fever, nursing women	Water-soluble, effect is outweighed by sugar and alcohol	13 - 16 mg
Vitamin B5(Pantothen acid)	Liver, vegetable, wheat germs, asparagus, crabs, meat, sunflower cores, Pumpernickel	Against turning grey, hair loss, hair and mucous membrane illnesses, necessarily for the dismantling of fat, proteins and carbohydrates	Nerve malfunctions, bad healing of wounds, early turning grey, weakened immune system	Over urine excreted	Old people, pregnant and nursing women, burden, drinking much coffee an tea	Water-soluble, heat-sensitive	approx. 10 mg
Vitamin B6(Pyridoxin)	Bananas, nuts, wholemeal products, yeast, liver, potatos, green beans, cauliflower, carrots	Travel sickness, neuralgia, liver damage, premenstrual syndrome, digestion of protein, most important hormone in pregnancy together with folic acid, detoxication	(rather rarely) intestine problems, bad skin, tiredness, rough corners of the mouth	With intake of this for a longer time in form of tablets it can deposit in the body tissue and lead to nerve damages.	Period of growth, intake of birth control pill, cortisone, during physical and mental load, before the menstruation	Water-soluble, neither heat nor light-resisting	approx. 2 mg
Name	Main occurrence	Effectiveness	Lack	Overdosing	Increased need	Characteristics	Daily need
Vitamin B7(Biotin, Vitamin H)	Liver, cauliflower, champignons, wholemeal products, eggs, avocado, spinach, milk	Skin deseases, loss in growth of hairs, liver damage, assists metabolism, carbohydrate and fatty acid activity, together with vitamin K it is needed for building up the clotting factors	States of exhausting, skin inflammations, muscular pains, hair loss, nausea	not known	Intake of birth control pill, antibiotics and cathartics	Water-soluble	approx. 0,5 mg
Vitamin B9(Folic acid, Vitamin M)	Liver, wheat germs, cucurbit, champignons, spinach, avocado	Liver damage, cell division, healing and growth of muscles and cells, protein metabolism	Anaemia, digesting disturbances, disturbances of hair -, bone and cartilage growth	Allgergies, sleep disturbances and bad moods (with more than 15 mg a day)	Pregnant and nursing women, smoker, youth	Water-soluble, do not tolerate with heat, light or oxygen	approx. 160 µg
Vitamin B12(Cobalamin)	Liver, milk, yolk, fish, meat, oysters, quark, barm	Building substance of cytoblast and erythrocyte, nerve pains, skin and mucosa inflammation, liver damage	Aenaemia, nerve disturbances, nervous disturbances, changes in the lung and the spinal marrows	Not possible, because it will be excreted by the body	Diabetics, pregnant and nursing women, vegetarian, vegan, intake of birth controll pill, antibiotics and anti cramp means, chemotherapy	Not water-soluble, heatproof	approx. 5 µg
Name	Main occurrence	Effectiveness	Lack	Overdosing	Increased need	Characteristics	Daily need
Vitamin C(ascorbic acid)	Dogroses, sea buckthorn, citric fruits, black currants, potatoes, paprika, tomatoes, collard, spinach, vegetables, radish	Inflammation and bleeding-restraining, assists the body's defences, protects cells against chemical destruction, activates enzymes, structure of connective tissue, bones and dental enamel, faster healing of wounds, stabilisation of psyche	Gum-bleed, tiredness, joint pain and headache, bad healing of wounds, lack of appetite, scurvy, inefficiency	In the case of overdosing in form of powder and pills nausea, vomiting and urine stones can be the result.	Smoker, pregnant and nursing women, older people, diets, alcohol consumption, intake of birth control pill, antibiotics, cortisone, analgesics and barbiturates	Water-soluble, oxygen and dryness-sensitively, not for a long time store	approx. 75 mg - 200 mg
Vitamin D(Calciferol)	Cod-liver oil, liver, milk, yolk, butter, sea fish, herring, champignons, avocado	Regulation of calcium- und phosphat household, structure of bone, assits admission of calcium	Bone curvature and softening, increased infection sensitivity, amyasthenia	(only with man-made Vitamin D) Calcium deposists in bones, heart muscle, blood vessels, stomach, headache, vomiting, swindle, gastro-intestinal diseases	Babies, older humans, intake of birth control pill, cathartic, antibiotics, barbiturate	Fat-soluble, light sensitively, heatproof	approx. 5 µg
Vitamin E(Tocopherole)	Sunflowers -, corn -, Soja and wheat germ oil, nuts, flaxseed, salsify, peperoni, collard, avocado	Stabilization of the immune system, anti-inflammatory, cell replacement, protection from radicals, modulates cholesterol level and hormone household, important for blood vessels, muscles and reproduction organs	(rarely) amblyopia, tiredness, amyotrohia, dislike, reproduction problems	(particularly by synthetically manufactured caps) bad healing of wounds, deficiency symptoms, swindle, nausea	intake of cathartics and blood-fat-lowering medicines, high consumption of alcohol	Fat-soluble, it is destroyed by open storage, deep-freezing or cooking with much fat	10 - 30 mg (with fat-enrich nutrition more)
Vitamin K(Phyllochinone)	Eggs, liver, green collard, green vegetable, bulbs, oatmeal, kiwi, tomatoes, cress	Necessary for formation of the blood clotting factors	High doses of vitamin A and E work against vitamin K.	With intake for a longer time, it can become toxid, bleedings, hot flashes, renal diseases	Babies, high consumption of alcohol, intake of birth control pill, antibiotics and carthartics	Fat-soluble, food with Vitamin K schould be stored darkly	approx. 2 mg

LIPIDS or FATS

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Lipids are the group of fats and fat like substances. They are the compounds of carbon, hydrogen and oxygen but they differ from carbohydrates in that the hydrogen and oxygen are not in the same proportions as in water. They are insoluble in water but soluble in organic solvents like acetone, ether, alcohol, etc.They needs a large amount of oxygen for their oxidation to release energy. True lipids are esters of fatty acids and an alcohol.

Sources of fats – the principal sources of fats in our diet are cooking oil, butter, ghee, oil seeds, milk, mutton, cheese, eggs, etc.

Classification of lipids – lipids are grouped into three categories:

(a) Simple lipids

(b) Complex lipids

(a) Simple lipids – these are various types of fats, oils or waxes.

(i) Fats: These are esters of fatty acids and glycerols. These are also called as triglycerides. Each molecule of glycerol can react with three molecules of fatty acids. Depending upon number of fatty acids attached they are called mono, di or triglycerides.

· Monoglyceride- one molecule of glycerol + one molecule of fatty acid.

· Diglyceride- one molecule of glycerol + two molecules of fatty acids.

· Triglycerides- one molecule of glycerol + three molecules of fatty acids.

(ii)Oils: These are fats, which are rich in unsaturated fatty acids (fatty acids with more than one double bond)

Importance of oils – Because of the presence of unsaturated fatty acids they are recommended to people who are suffer from high blood cholesterol of cardio- vascular diseases, they tend to lower the high blood cholesterol without raising the fat. The cholesterol leads to thickening of arteries, which became a cause of high blood pressure.

(iii) Waxes – These are esters of long chains fatty acids and long chains alcohol other than glycerol. They are mainly protective in functions and form water soluble coating on hair and skin in animals and on stems, leaves and fruits of plants.

(b) Complex lipids – These lipids are complex as they are formed in association of either of carbohydrates or phosphates or proteins.

(i) Glycolipids – These are formed by association of lipids with carbohydrate molecules. These are found in membranes.

(Glycolipids = lipids +carbohydrate)

(ii) phospholipids- These are lipids containing a phosphate group.(phospholipids= lipids + phosphate)

(iii) Lipoprotein – These are lipids associated with proteins molecules.(lipoproteins = lipids + proteins molecules)

c. Derived lipids – These include hydrolyzed products of simple and complex lipids.e.g. – Steroids (cholesterol).

Steroids - Steroids are composed of fused hydro- carbon rings and a long hydrocarbon chain.e.g. Cholesterol, Diosgenin.

Importance of cholesterol - It is a steroid lipid. It is said to create abnormal thickening of walls of arteries. It can raise blood pressure and hence may lead to circulatory problems. It is said that is not bad but not useful as well.

Importance of steroids –

(i) Cholesterol is a precursor molecule of many sex hormones like progesterone, testosterone and adrenocortico- tropic hormones.

(ii) Cholesterol on irradiation by ultraviolet rays forms vitamin D necessary for growth of bones.

(iii) Diosgenin is used in the manufacture of anti- fertility pills.

Function of lipids

· Lipids as rich source of energy – Lipids provide the energy fuel. The caloric value of 1gm of fats is 9.45 k cal while the physiological fuel value of 1 gm of fats is 9.0 k cal.

· As heat insulator – Fats are deposited in the subcutaneous tissues. These acts as insulator.

· As food reserve – Triglycerides stored in adipose tissue as principal food reserve.

· As solvent – Lipids acts as a solvent for fat- soluble vitamins like- A, D, E and k.

· Acts as cushions – They absorb mechanical impact around organs like eyeball.

· Phospholipids- They form constituents of membranes of various organs.

· Glycolipids- They form components of cell membranes and myelin of nerve cells.

PROTIENS

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Proteins are made up of large number of amino acids linked together chemically.

Proteins are most complex chemical compounds formed of C, H, O,N, S, P. The characteristic element is the nitrogen . All the reactions in the body are controlled by proteins, known as enzymes.

Proteins are made up of some 20 different naturally occurring amino acids linked together chemically. They are polymers made up of chains of amino acids. These amino acids are linked by peptide bond or peptide linkage. During digestion, these proteins are broken down into amino acids and absorbed through the intestinal wall.

Sources of Proteins- Principal sources of proteins are pules, meat, fishes,eggs, milk soya bean, cereals, etc.

Daily Requirements- An adults person needs on an average about 70-100gm of proteins per day. The growing children and protein. Approximately 15% of proteins should be present in human diet.

Categories of proteins: On basis of chemical nature, proteins are divided into three categories -

(a) Simple proteins - These are formed of peptide chains ans yield only amino acids on hydrolysis. examples are albumin, globulin, histones, protamines, etc.

(b) Conjugated proteins - These are the proteins formed in combination with glucose (glycoproteins), lipid(lipoproteins), phosphate (phosphoprotein0, etc. examples are casein, blood antigens, haemoglobin of RBCs, etc

(c) Derived proteins - These are the protiens which are formedby partial hydrolysis of simple proteins. examples are peptones, proteoses, etc.

AMINO ACIDS- Proteins are the polymers made up of chains of amino acids. Thus amino acids are building blocks of protiens. many amino acids are linked one another to form protein. hence, amino acids are called monomers of proteins. It consists following characteristics:

These are the basic units of protiens.
All amino acids have at least one acidic caboxylic group (- COOH) and one basic amino group(-NH2).
These are colorless, crystalline solids.
These are soluble in water and insoluble in organic solvents.

Examples of amino acids are alanine, glycine, serine, leucine, isoleucine, etc. the simplest amino acid is glycine.

Formation of peptide bond: A peptide bond is formed when two amino acids are joined together by a peptide bond. A polypeptide is formed when numbers of successive amino acids are joined together in a long chain of peptide bond.

Categories of amino acids : There are 20 types of amino acids. on tha basis of nutritional value, they are divided into two categories.

(i) Essential amino acids : These are the amino acids which are not synthesized in the body. therefore, they must be included in diet. These are leucine, isoleucine, lysine, phenylalenine, trytophan, valine, methionine, and threonine. These are eight in number.

(ii) Non essential amino acids - These are the amino acids which are synthesized in the body. they may or may not be present in the diet. These are alanine, serine,glycine, glutamine, tyrosine, asparatic acid, cysteine, arginine, histidine, proline, glutamic acid and asparagine.

Functions of protein: Proteins as building blocks- Many proteins act as structural proteins ans take part in building and repairing of the body tissues. Therefore, these are essential for the growth.

Proteins as energy - Proteins provide energy fuel. The caloric value of 1 gm of protein is 5.654 kcal while the physiological fuel value of 1gm of proteins is 4.0 kcal.
Proteins as enzymes - These act as enzymes or bio-catalyst which regulate life processes. Nearly 2000 different kinds of enzymes are known as far.
Protein as hormones - Some hormones are proteins, such as insulin (a hormone regulating glucose balance).
Protein as defensive - Some proteins are antibodies or immunoglobins. They neutralize the foreign bodies and develop immunity.

5. Thrombin and fibrirogen cause blood clotting.

Diseases due to protein deficiency - The proteins are essentials for the body growth. their deficiency in the diet causes retardation of physical growth and mental growth. Deficiency of proteins causes two diseases in infants; marasmus and kwashiorker.

CARBOHYDRATES

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           There are mainly compounds of carbon, hydrogen and oxygen. Hdrogen and oxygen are generally occuring in the ratio of 2:2, thus known as hydrates of carbon (CH2O). The general formula of carbohydrates can be written as Cn(H2O)n.

Sources of Carbohydrates: Carbohydrates are found in wide variety in wide variety of foods. Its important sources are cereals (wheat, maize, rice), potatoes, sugarcane, fruits, breads, milk, etc.
Daily Requirement- A healthy adult person requires on average 500g carbohydrates per day. Approximately 55-75% of total food calories should be taken in form of carbohydrates. Carbohydrates requirements may be more for athletes, mountaineers, labourers, etc.
Categories of Carbohydrates- Carbohydrates are classified according to the complexity of chemical substances of which they are formed. They are grouped into:
              (a) Monosacccharides
              (b) Disaccharides
              (c) Polysachharides
(a) Monosaccharides
(i) These are chemically simplest forms of carbohydrates in which carbohydrates can exists.
(ii) They cannot be hydrolyzed into smaller carbohydrates.
(iii) Common examples are glucose, fructose, and galactose.
(iv) They are simple sugars, composed of 3-7 carbon atoms
(v) They are classified according to number of carbon atoms.

NUTRITION

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The sum total processes of taking in, digestion, absorption, and assimilation of food are known as nutrition. It is important because-
(i) it provides energy to the body to perform various activities,
(ii) it provides essential materials for growth,
(iii) it maintains the body temperature.

Types of Nutrition
There are two main types of nutrition:
(a)Autotrophic or holophytic nutrition: It is the process by which organisms can synthesize their food by process of photosynthesis. It is found in green plants. The green plants possess chlorophyll pigment. It helps plants to trap solar energy and manufacture the food (in form of simple sugar) by utilizing simple inorganic materials of nature . Such organisms are known as autotrophs.

(b)Heterotrophic nutrition: It is the process by which organisms cannot synthesis their food by themselves. They are dependent on autotrophs directly or indirectly. They are found in all animals and non-green plants like fungi and bacteria.Such organisms are known as heterotrophs . Depending upon the mode of feeding, there are three types of heterotrophic nutrition:
(i) Holozoic nutrition- organisms like man depend on solid food materials.
(ii) Saprozoic nutrition- organisms like fungi, some bacteria, etc.
(iii) Parasitic nutrition- organisms like Ascaris, tapeworm, etc. depend either or completely on their hosts. They are called parasites.

Nutritional Requirements
Before discussing the digestive system, it is necessary to have an understanding of the body regarding nutrition i.e. the dietary constituents and their functions within the body.

Food and Nutrients- Food can be defined as any essential substance that when absorbed into the body tissues, yields material for the production of energy, growth and repair of tissues and regulation of life processes.

Functions of food

acts as a fuel to provide energy,
promotes body function,
provides essential materials for growth and reproduction,
helps in repair of body tissues,and
develops immunity against diseases.

Components of food
The food of an animal consists of mainly six types of food components-

(1) Carbohydrate    (2) Proteins

(3) Fat                     (4) Vitamins

(5) Minerals           (6) Water