Chemical Basis of Life PDF

Biology Chemical Basis of Life 01 The bodies of all organisms are composed of variety of chemical compounds. These chemical compounds are formed by the bonding of naturally existing elements in different ways. There are on...

Biology Chemical Basis of Life 01 The bodies of all organisms are composed of variety of chemical compounds. These chemical compounds are formed by the bonding of naturally existing elements in different ways. There are only about 25 elements in the living body out of the 92 elements present in nature. They are present at different locations in the body in different forms. The most common 4 elements in the living body are Carbon, Hydrogen, Oxygen & Nitrogen. Other than above Sulphur, Phosphorous, Sodium, Potassium, Calcium, Magnesium, Iron and Chlorine are essential for the survival of organisms. The below diagram 1.1 shows the percentages of main elements in the human body. 3] 4] 10] Oxygen Tlaiscka 18] Carbon ldnka 65] Hydrogen yhsv%cka Nitrogen khsg%cka Others fjk;a Fig. 1.1- percentages of 4 common elements in the human body (mass basis) Chemical compounds that build up living matter can be divided into two categories as orgonic compounds and inorganic compounds. Compounds which contain carbon are known as organic compounds and compounds which do not contain carbon are known as inorganic compounds. Those organic compounds that build up the living body or living matter are known as biological molecules.There are four types of biological molecules. They are: ² Carbohydrates ² Proteins ² Lipids ² Nucleic acids 1 For free distribution Water, minerals and gasses are some of the inorganic molecules that are essential for the maintenance of life. For extra knowledge Element Percentage Locations present in human body based on mass% O 65 All fluids,tissues, bones, proteins C 18 everywhere in the body H 10 All fluids,tissues,bones,proteins N 3 All fluids,tissues,proteins Ca 1.5 Brain, lungs, kidneys, liver,heart,tyroid gland,muscles,bones P 1.0 Urine,bones K 0.35 Enzymes S 0.25 Proteins Na 0.15 All fluids,tissues Mg 0.05 Brain, lungs, kidneys, liver,heart,tyroid gland,muscles š Cl Fe Micro elements I 1'1 Carbohydrates This is the most abundant organic compound on earth. They are produced during the photosynthesis of green plants. Potato, sweet potato, grains, sugar, flour are examples for foods which contain carbohydrates. The main elemental composition of carbohydrates is Carbon (C), Hydrogen (H) and Oxygen (O). Hydrogen and oxygen combine in 2:1 ratio in carbohydrates. Common molecular formula Cx (H2O) y 2 For free distribution ² Monosaccharides Type of Location it's Other facts monosaccharide present 3 For free distribution ² Disaccharides Two Monosaccharides join to form a Disaccharide. During this process a water molecule is released. In the same way relevant Monosaccharides can be obtained by hydrolyzing Disaccharides. Disaccharides are sweet, water soluble crystals. 2 C6H12O6 C12H22O11 + H2O Maltose,Sucrose and Lactose are examples for disaccharides. The characters of disaccharides are discussed in the table below. Table 1.2 Characters of different types of disaccharides Type of Location it's Other Facts disaccharide Present Maltose Germinating Union of two glucose molecules seeds forms a Maltose molecule. Glucose ¬ Glucose Maltose ¬Water An intermediate product of starch hydrolysis Sucrose White & brown Union of a Glucose molecule with a Fructose Sugar molecule forms a Sucrose molecule Sugar cane & Glucose ¬ Fructose Sucrose¬Water Beet Some fruits Phloem sap Lactose In dairy products Union of a Glucose molecule with a Galactose molecule forms a Lactose molecule Galactose ¬ Glucose Lactose¬Water The only sugar that is absent in plants Not sweet as Sucrose The percentage of Lactose in cows milk according to the composition is 4% - 6% The percentage of Lactose in human milk according to the composition is 6% - 7% 4 For free distribution ² Polysaccharides Polymerisation of a large number of monosaccharides form a polysaccharide molecule. Hydrolysis of Polysaccharide results relevant monosaccharides. Insoluble in normal water. They are not crystals. Cellulose, starch and glycogen are examples for polysaccharides. The structural unit of cellulose, starch and glycogen is glucose , but their properties are different according to the number of glucose molecules and how they are bound with each other. The characters of polysaccharides are discussed in the table below. Table 1.3 - Characters of different types of polysaccharides Type of Location it's Other Facts polysaccharide Present Cellulose Cell wall of No nutritional value, as it is not digested plant cells in the human digestive system. Therefore In fibers it helps to avoid constipation Starch Grains, Yams, The type of carbohydrate that stores in Jak, Bread plants is starch Fruit Glycogen Animal liver & yy The type of carbohydrate that stores in muscles animal body is Glycogen For extra knowledge Fig.1.2 - Structure of a glucose molecule 5 For free distribution ² Significance of Carbohydrates yy As an energy Source The main source to obtain energy for the activities of organisms is the carbohydrate.The Monosaccharides (Glucose) produced due to hydrolysis of those compounds release energy during oxidation. yy As storage compound yy As a structural component in organism yy As a constituent of Nucleic acid Tests to identify Carbohydrates The below mentioned tests can be conducted to test Starch, Monosaccharides & Disaccharides which are some of the identified Carbohydrates. Starch test yy Obtain small amount of food & grind well with water. yy Add a drop of Iodine solution to the above solution. Observation (- Purplish blue colour appears Test for Monosaccharides & some Disaccharides yy Obtain a solution of Gluscose, into a test tube. yy Add few drops of Benedict solution to the above solution. yy Immerse the above solution in a water bath and heat. yy Can observe colour change as below. (- Blue Green Observation Green Orange Brick red yellow precipitate Disaccharides (Sucrose) yy Obtain a sucrose solution into a test tube. yy Add few drops of Benedict solution to it. yy Immerse the test tube in a water bath & heat it. yy No colour change. yy Then add few drops of diluted Sulphuric acid (H2SO4) & heat. (- Blue Green Observation Green Orange Brick red yellow precipitate 6 For free distribution 1.2 Proteins Protein is an essential constituent in all living cells. Carbon(C) Hydrogen (H), Oxygen (O) & Nitrogen (N) are always present in proteins. Sometimes Sulphur can also be present. 17% of the mature human body is composed of proteins. Protein is a complex molecule made up of polymerized amino acid molecules. Meat,fish,egg white cereals are some of the foods rich with proteins. For extra knowledge yy Amino acids Below is the structure of a typical amino acid molecule. R weuhsfkda ldKav Amino Carboxyl ldfndla is,a ldKavh NH2 C COOH group group H R-represents a group containing both Carbon (C) and Hydrogen (H). Due to the change in R group, 20 different amino acids are present. All proteins present in organisms from bacteria to human are made up of these 20 different amino acids combined in different sequences. The simplest Amino acid is Glycine. Here Hydrogen (H) is present as the R group. H H C NH2 COOH Some amino acids cannot be synthesized within the body. So they have to be taken from outside with food. Therefore they are known as essential amino acids. , 7 For free distribution  For extra knowledge Significance of Proteins yy As an energy source When energy supply from Lipids and Carbohydrates is not sufficient protein is used in energy generation. yy To make structural components Proteins are important components in making cell membrane. Other than that collagen protein is a component of connective tissues in animals. Hairs & feathers also contain keratin protein. yy As enzymes All the bio-chemical reactions take place in organisms are catalyzed by enzymes. The enzymes are proteins. yy As hormones Some hormones are proteins which involve in homeostasis & coordination of organisms. Eg : Insulin, Growth hormone yy As antibodies The antibodies that are produced in the body to protect the body against microorganisms that enter into the body are proteins. 8 For free distribution Test to identify proteins Biurette test ŒŒ Obtain a solution made by grinding dhal or an egg yolk into a test tube. ŒŒ Add an extra amount of Sodium hydroxide (NaOH) and then add few drops of Copper Sulphate (CuSO4) Observation - Solution turn to pinkish purple or dark purple colour Enzymes The special proteins (organic catalysts) that are produced within the organism to increase the rate of bio- chemical reactions are known as enzymes. For example to convert sucrose into Glucose, sucrose has to be heated with a dilute acid. But the enzymes present in the digestive system do the same reaction at a low temperature. Therefore the activity of enzyme is to catalyze the bio- chemical reactions. Activity - 01 Activity of Amylase on starch Method yy Put 2ml of starch solution into a test tube. yy Add 2ml of amylase into it and mix well. yy Get a drop from the solution after 2 minutes and place it on a white porcelain tile and add a drop of iodine onto the drop of mixture. yy Continue same procedure for about 20 minutes in 2 minute intervals. Observation The blue colour of the drop obtained from the mixture gradually reduces with time and finally obtains the colour of Iodine (yellow /brown colour) That is due to Moltose produced in starch hydrolysis with Amylase enzyme. Starch gives black blue colour with iodine but it does not give colour change with iodine after 20 minutes as there is no starch there.That is because starch is changed into another compound by Amylase. 9 For free distribution 1'3 Lipids Fats & oils belong to this group. (Lipids which are solid at room temperature are called fats and liquids are called oils.) Similar to carbohydrates, fats also contain Carbon, Hydrogen & Oxygen as constituent elements. But the ratio of hydrogen to oxygen in fats are very much higher than carbohydrates. Lipids are insoluble in polar solvents including water. They are soluble in organic solvents. Ground nut, coconut, gingelly, butter and margarine are examples for foods which contain lipids. Fatty acids & glycerol react to form Lipids. Fatty acids ¬ glycerol Lipids ¬ Water Significance of Lipids yy As an energy source Lipids act as an energy source as carbohydrates & proteins. More energy is produced during burning of lipids. yy To form different structural components Lipid is one of the most important compounds in cell membrane. (Specially phospho lipids & cholesterol) yy For conservation of water The wax known as cutin present on the surface of the plant body conserve water. Most animals' body covering also contains wax which helps to avoid desiccation as it is impermeable to water. yy To maintain the body temperature Warm blooded animals such as birds and mammals possess a hypodermal fat layer which acts as a thermal insulator. It helps to maintain their body temperature. yy To protect internal body organs The fat layer surrounds the organs & structures in the body and absorbs external shocks. Thereby provides protection. yy To synthesize some hormones Some Hormones of vertebrates (Oestrogen, testosterone, Cortisol) are lipid compounds. 10 For free distribution Test to identify lipids Sudan III test Put some amount of gingelly oil or coconut oil into a test tube. yy Add sudan III reagent into it. Observation - Appearance of red fat globules Conclusion - Lipid present in that food For extra knowledge Fatty acids can be divided into two groups as follows. fatty acids saturated fatty acids unsaturated fatty acids Saturated fatty acids fatty acids where the Carbon atom contains the maximum number of Hydrogen atoms are called saturated fatty acids. Saturated fatty acids exist in room temperature as solids or semi-solids. Unsaturated fatty acids fatty acids where the Carbon atom does not contain the maximum number of Hydrogen atoms are called unsaturated fatty acids. Unsaturated fatty acids exist in room temperature as liquids. 1'4 Nucleic Acids Nucleic acid is the most important molecule out of the main biological molecules in living matter in genetical aspect. It is a linear polymer made up of large number of nucleotides. It contains Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) and Phosphorous (P). 11 For free distribution Each nucleotide is made up of 3 components.They are; 1. Nitrogenous base 2. Pentose sugar group fmdia f*aÜ Phosphate 3. Phosphate group Nitrogenous base khsg%ckSh NIa uh Pentose fmkaSuger fgdaia groupe iSks Fig. 1.3 - A nucleotide Nucleic acids are mainly of two types. DNA - Deoxy ribo Nucleic Acid RNA - Ribo Nucleic Acid DNA The structural unit of DNA is Deoxy ribo Nucleotide. DNA transfers genetic chracteristics from generation to generation RNA Except DNA, the other nucleic acid present in organisms is RNA. The structural unit of RNA is Ribonucleotide. Protein synthesis is the function of RNA. Fig.1.4- The structure of a DNA molecule Significance of Nucleic acidI yy Important in storage of genetic information of organisms. yy Important in transferring genetic information from generation to generation. yy Important in protein synthesis process. yy Important in controlling all cellular activities in a cell. The information to control cellular activities is present in DNA. yy RNA is important in storing genetic information of some viruses. yy The variations occur in DNA due to mutations are important in evolution. 12 For free distribution The above biological molecules contain mainly Carbon (C), Hydrogen (H),Oxygen (O) & Nitrogen (N). We will conduct below mentioned activities to confirm the presence of those elements. Activity - 02 Identification of water as a constituent in food Materials required Meat, Egg shell, Plant leaves, Crucible Method yy Grind /crush meat, egg shell, and leaves separately. yy Put them into crucible & heat them separately till they burn. yy During burning, hold a glass sheet above the crucible. yy Use cobalt chloride to identify whether the liquid drops on the glass is water. Observation yy Blue coloured Anhydrous cobalt chloride turn to pink Can confirm that water is formed on the glass sheet. Therefore the food that is used for the experiment contains water as a constituent. Activity - 03 Identification of presence of Carbon(C) in bio-molecules Materials required yy Several crucibles, plant leaves, piece of fish, rice. Method yy Make pulps by crushing all above materials separately. yy Put them separately into crucibles and heat well. yy The final residue obtained should be rubbed against a white paper. Observation yy Get lines drawn due to coal Can confirm the food that is used for the experiment contains Carbon (C). 13 For free distribution  Activity - 1'4 Identification of presence of Nitrogen(N) in bio-molecules Materials Required Two test tubes, solution of sodium hydroxide, solution of copper sulphate, egg white, piece of fish. Method yy Crush fish thoroughly, add water and mix well. Filter the solution. yy Put 2ml of the fish extraction and egg white in to separate test tubes. yy Add equal volume of sodium hydroxide. yy Add few drops of copper sulphate to it. Observation yy Purple colour appears in the solution The above observation confirms the presence of protein in food. As Nitrogen is a constituent of proteins,it is confirmed that the above tissues contain Nitrogen. 1'5 Water The highest proportion of the body mass of living organisms is composed of water which is an inorganic compound. 2/3 rd of the body weight of most of oranisms is by water. water is an essential medium for the maintenance of living matter. The table below, shows the specific properties of water and contribution of them to the maintenance of life. Assignment - 1.1 Collect information about water using internet, news papers and other journals. Present those information about water to the class. 14 For free distribution  Table 1.4 - Specific properties of water and its contribution for the maintenance of life Specific Property The contribution for the maintenance of life A good solvent yy Provides a medium for bio-chemical reactions in the cells of organisms. yy The main constituent in the extra-cellular fluids of organisms. yy Facilitates removal of excretory material & fecal matter of animals. Act as a respiratory yy Important in respiration of aquatic medium organisms as Oxygen (O2) is soluble in water. Helps to regulate body yy Due to high specific heat capacity the body temperature. temperature does not fluctuate quickly with changes in the environment. As a transport yy Being the main constituent of blood,it helps medium to transport nutrients, vitamins & hormones to relevant locations. yy Transports water to the upper parts of the plant due to high cohesive & adhesive force of water molecules As a living yy Density of water is higher than density of environment for ice. When ice is formed they come to top organisms layers of water keeping water as it is in the bottom. This provides living environment for aquatic organisms. 1'6 Minerals Minerals are important as a nutrient constituent to maintain the life processes of organisms. They are absorbed as trace or macro elements into the body. The elements needed in higher amounts are known as macro elements and the elements needed in small amounts are known as trace elements. 15 For free distribution 7% of the body weight is by minerals. ¾ th of the above amount is by Calcium and Phosphorous. Other than that Potassium, Iron, Magnesium, Copper & Chlorine are also included. The elements are required in small amounts. But when they are not present in correct amounts, plants and animals show deficiency symptoms. Table 1.5 - Functions of minarals in human body and deficency symptoms of them Element Functions Deficiency Symptoms Controls the ionic balance of the fluid in the cell For the activity of heart and Weakening of muscles Potassium muscles Psychological disorders Transmission of nerve impulses Activates enzymes Constituent of digestive juice Respiratory disorders Sodium To maintain constant osmotic Cramps pressure in cells Nausea Transmission of nerve impulses Diarrhoea Magnesium Constituent of bones and teeth High heart beat To control nerve activity in Nerve irritability skeletal muscles Help in metabolic activities Calcium Growth of bones & teeth Rickets Blood clotting Weakening of bones & Proper function of nerves teeth Milk production Growth disorders Absorption of Vitamin B 16 For free distribution  Phosphorous Growth of bones & teeth Weakening of bones & As a constituent of nucleic become fragile acid For carbohydrate & fat metabolism Instant release of energy in muscles & nerves Iron Synthesis of haemoglobin Anaemia Storage of oxygen in muscles Sleepiness As a constituent of enzymes Hypoactive nature weakness in psychological development Iodine Synthesis of Thyroxin Affects development of hormone intelligence Lethargic attitude towards studies Limits body height Functions of minerals in plants & deficiency symptoms of them are mentioned in the following table. Table 1'6 - Functions of minerals in plants & deficiency symptoms of them Element Functions Deficiency Symptoms As a constituent of amino acid, proteins, Retardation in growth Nitrogen nucleic acid and chlorosis in leaves chlorophyll Retarded growth of roots Phosphorous As a constituent of nucleic acid & ATP Red and purple patches on leaves Protein synthesis Chlorosis in leaves Potassium Opening & closing of Yellow or brown patches in stomata leaves As a constituent of Chlorosis in veins & areas Sulphur amino acids & proteins between veins. 17 For free distribution  Synthesis of chlorophylls Iron Synthesis of respiratory Chlorosis in tender leaves enzymes Component of cell wall To maintain the structure Death of tissues and tips of the Calcium & functions of plasma leaves membrane For the Activity of enzymes For the activity of most Dead cells & tissues Zinc enzymes Synthesis of throughout the plant. Extra chlorophyll thickness in leaves Nitrogen deficiency symptoms Zinc deficiency symptoms Phosphrous deficiency symptoms Potassium deficiency symptoms Calcium deficiency symptoms Fig 1.5 - Deficiency symptoms in plants Assignment 1.2 Observe a field or a farm & collect different parts of plants with different deficiency symptoms. Identify the deficient element for the relevent disease condition. (Make sure not to harm the cultivation) 18 For free distribution 1'7 Vitamins They are organic compounds important in bio chemical reaction. Vitamins can be classified into 2 groups according to the solubility in water. Vitamin B & C are water soluble and A, D, E, & K are insoluble in water. But these are fat soluble. The vitamins are needed for activities of human body, Their uses and deficiency symptoms are given in the table below. Table 1.7 - Uses of vitamins and their deficency symptoms Type of Use Deficiency Symptoms Vitamin Vitamin A Night blindness Formation of visual Bito patches in the eye pigments Dryness in the skin important in eye vision Blisters on knees & elbow To keep skin healthy & fair Diseases associated with respiratory tract Vitamin B Maintenance of nerves Beri beri To maintain a healthy Anaemia skin Dryness in skin Formation of bone change in complexion marrow Reduction in antibody production Maturation of RBC Antibody production Vitamin C To keep skin healthy Weakening of gum To form enamel. Internal bleeding To synthesize collagen Delays recovery from diseases fibers. Scurvy Vitamin D Controls absorption of Tooth decay calcium & phosphorous Osteoporosis Vitamin E Growth of tissues & Premature births cells Increase rate of breaking down of red blood cells Weaknesses in cell division Weaknesses in reproduction 19 For free distribution Vitamin K To produce components Delays blood clotting needed for blood clotting For knowledge Vitamin B is a complex vitamin. There are vitamins as B1" B2, B6, B12 in that complex' these are obtained through food and some vitamins are synthesized by bacteria living in human intestine. Vitamin A deficiency symptoms Vitamin B deficiency symptoms Vitamin D deficiency Vitamin C deficiency symptoms symptoms Fig 1.6 - Deficiency symptoms of vitamins 20 For free distribution  Summary yy The main substances that form the living body are carbohydrates, proteins, lipids & nucleic acids. They are known as biological molecules belong to living matter. yy Beside organic compounds, inorganic compounds such as water, mineral salts also play an important role in living systems. yy Main elements found in biological molecules are C,H,O,N. yy The proteins that catalyze biochemical reactions are enzymes. yy Although Minerals & vitamins are needed in small amounts, when they are deficient in supply, organisms show deficiency symptoms. yy The specific properties of water are highly important in maintenance of life. Exercises 01. Select the most appropriate answer. (1) The food that contains highest amount of starch is 1. Potato 2. Peanut 3. Cucumber 4. Gotukola (Centella) (2) Which belongs to monosaccharide? 1. Fructose 2. Sucrose 3. Maltose 4. lactose (3) A carbohydrate specially found in plants is 1. Glycogen 2. Lactose 3. Pectin 4. Cellulose (4) A Vitamin that helps in blood clotting is 1. Vitamin A 2. Vitamin D 3. Vitamin C 4. Vitamin K (5) Not an organic compound present in living body, 1. Proteins 2. Water 3. Carbohydrates 4. Lipids 21 For free distribution 02. Below mentioned deficiency symptoms were identified at a health clinic conducted for grade 6 students in a particular school. Identify the relevant vitamin for the deficiency symptoms. yy Weaknesses in eye sight & bito patches in eyes.………………………….. yy Weaknesses in growth of teeth & tooth decay.………………………….. yy Bleeding gum ………………………….. yy Wounds at ends of mouth ………………………….. yy Anaemia ………………………….. (03) State 3 specific features of water. Explain one briefly mentioning how it helps in continuation of life. (04) “It is important to contain fibres in food” give the reasons for it. Technical terms Biological molecules - ffcj wKq - E°›¯À ‰»UTÖ Enzymes - tkaihsu - ö|õv¯® Catalysts - W;afm%arl - FUQ 22 For free distribution