Constituents of Living Bodies
Living beings contain a large variety of chemical compounds. They mainly contain organic compounds (compounds of carbon) along with water and some inorganic compounds. Major organic compounds present in living bodies are carbohydrates, lipids, proteins and nucleic acids.
Some principles that are characteristic of living state are as follows:
1) All living organisms use same kind of building block molecules. Hence, they have a common ancestry.
(2) Biological molecules have a basic simplicity in their structures.
(3) All biomolecules have specific functions in cells.
(4) All living organisms are dependent on each other through exchanges of energy and matter via the environment.
(5) The energy needs of all organisms are provided by solar energy.
(6) Living cells act as chemical enzymes that function at constant temperature.
(7) The identity of each organism is preserved due to their distinctive sets of nucleic acids and of proteins.
Classification of Constituents of Living Bodies
Living bodies include animals and plants. The tissues of animals and plants are made up of water, organic compounds and inorganic compounds. The constituents of living bodies are mainly divided into two parts water and dry matters. Most of the plants do not have definite amount of water. It varies from 60-90%. The dry matters have organic and Inorganic components.
The classification of living bodies both plants and animals can be depicted in tabular form as below :
The various constituents of living bodies can be described as under :
Water is a most important constituent of living organisms. They contain 50-95% water. The percentage of water is not fixed but it varies in the living bodies. Plants have bout 75% water. Water algae contains water 95 to 98%.
The main functions of water are as under:
(i) Water acts as a universal solvent.
(ii) Water dissolves plant nutrients and carries them to different parts of the plants.
(iii) Water is required by the plants for making their food by photosynthesis. During photosynthesis green plant produce carbohydrates from water and CO2, in presence of sunlight.
(iv) Plants synthesis sugars, fats, proteins and other substances in presence of water. These substances form plant cells.
(v) Water controls the temperature of living bodies. It keeps the body temperature unchanged when there is a change in temperature of the environment.
(vi) It dissolves the waste and toxic substances and excretes from the body of the living beings.
(vii) It is a main constituent of protoplasm in the animal body. It is essential for proper functioning of muscles and joints.
(vii) It is essential for blood circulation in animals.
(ix) The actions related to sound transmission and vision take place in the presence of water in animals.
(x) Water taken with food decreases the growth of harmful bacteria in the body.
2. Dry Matters
Dry matters in the living bodies may be of inorganic as well as organic nature.
Animals and plants are found to contain inorganic elements such as N,P,K,Ca, Mg. S,Fe, Cu, Zn, Na, Mo, I and Cl. The bones and teeth of animals contain calcium and phosphorus. Plants too need Ca and P for their proper growth.
On burning dry matter of plants, organic matters are destroyed and plant ash is obtained. This ash contains the inorganic matters as nitrate, chloride, sulphate, phosphate, oxalate, citrate and tartarate salts.
The main functions of inorganic matters are as follows:
(i) Calcium and phosphorus are essential for the formation of bones and teeth in animals. They are also essential for plants.
(ii) Magnesium is the metal found in chlorophyll.
(iii) N, S and P are essential for the synthesis of amino acids.
(iv) Cobalt, Co is the metal found in vitamin B12.
(v) Iron, Fe is an integral part of haemoglobin in blood.
(vi) Oxygen gas is essential for respiration. (vii) CO2, and water form carbohydrates in plants by photosynthesis in the presence of light.
(viii) Some inorganic substances take part in metabolism in plants and animals. Potassium is required in protein synthesis.
The amount of organic matters in living beings is more than that in inorganic matters.The organic matters are of two types :
(i) Non-nitrogenous matters : They include carbohydrates, lipids, essential oil vitamins and pigments etc.
(ii) Nitrogenous matters : They include proteins, nucleic acids, enzymes, alkaloids and hormones etc.
1. Carbohydrates :Carbohydrates are found in large quantities in plants. They are found in plants as cellulose and in seeds as starch. Most of the carbohydrates have general formula Cx(H2O)y, Therefore, they were regarded as hydrates of carbon.
Glucose is present in all living cells. Lignin is found in cell wall in plants. Pectins which are colloidal polysaccharides with high molecular masses occur in plants and in roots, stems and fruits of trees. Glucose, sucrose, starch and glycogen are the carbohydrates which take part in metabolic reactions.
2. Lipids : Lipids are the triglycerides of higher fatty acids. They include oils, fats and waxes. Oils are liquid at 20° C Oils are found in oily seeds of mustard, coconut and linseed etc. Oils and fats are present in different seeds as stored food. The fat is constituted by three molecules of saturated higher fatty acids like palmitic acid (C15H33COOH) or stearic acid (C17H35COOH) and a molecule of glycerol but an oil is formed by three molecules of an unsaturated higher fatty acid like oleic acid (C17H33COOH) and a molecule of glycerol. Stearic acid part is found in most of the plant and animal fats.
Phospholipids, glycolipids and sterols are also found in living bodies. Plants contain the essential oils, resins and terpenoids.
3. Vitamins : Vitamins are the special type of chemical compounds synthesised by plants. These are quite essential for the proper growth of the body and maintenance of good health. Vitamins are of two types :
(i) Fat soluble Vitamins : Vitamin A, D, E and K.
(ii) Water soluble Vitamins : Vitamin B complex and vitamin C. Vitamins have limited functions in plants.
4. Pigments : Plants are known to possess some substance which are responsible for various colours. Such substances are known as plant pigments. Chlorophyll is mainly green pigment. It is essential for plants to make their food from CO2 and water in presence of sunlight due to photosynthesis.
The molecular formula of chlorophyll-a is C55H72O5N4 Mg and of chlorophyll-b is C55H70O6N4 Mg. Thus, chlorophyll has magnesium metal in its structure.
Carotenes and xanthophylls are the other pigments found in plants. a-carotene is found in carrots. Tomatoes are rich in lycopene.
Carotene is the precursor of vitamin A. The hydrolysis of carotene forms vitamin A in animals.
Xanthophylls are responsible for yellow colour. Maize is the rich source of Xanthophylls.
1. Proteins : Proteins are the main constituent found in living bodies. Proteins are a constituent of protoplasm. Proteins are synthesised by amino acids. Most of the proteins are made up of C, H, O and N. In some proteins, sulphur and phosphorus may also be found in small proportions. Pulses, milk, egg and meat are the rich sources of proteins.
2. Nucleic acids : These are long chain polymers of nucleotides.
Neucleotide = Base + Sugar + Phosphate
Since repeating units of nucleic acids are nucleotides, they are also called polynucleotides. Nucleic acids found in living bodies are of two types :
(i) DNA (Deoxyribo nucleic acid). It has deoxyribose as pentose sugar.
(ii) RNA (Ribonucleic acid). It has ribose as pentose sugar.
The bases present in nucleic acids are purines and pyrimidines. DNA molecules have the property to duplicate themselves. RNA molecules are responsible for the synthesis of proteins.
3. Enzymes : Enzymes are naturally occurring simple or conjugate proteins. They act as biocatalysts in cell processes in animals and plants. They are highly specific in their action. For example, invertase enzyme found in yeast converts sugar solution into glucose and fructose only. These are further converted into alcohol by zymase enzyme present in the yeast.
4. Hormones : Several types of hormones are found in plants and animals. Hormones are produced by ductless or endocrine glands. Plant hormones regulate the physiological process in plants. Insulin, thyroxine, adrenalin and ocytocin are important animal hormones. Auxins, gibberelins and cyctokinins are plant hormones. Most plant hormones are terpenoid compounds.
Besides the above compounds, plants are also found to contain alkaloids, chlorophyll and purines as nitrogenous compounds.