Introduction to Natural Sciences

Introduction to Natural Sciences Dr. Shwetha S Durgad Assistant Professor Christ Univeristy  Biochemical evolution Life appeared after a period of chemical reactions according to physical and chemical laws. It is presumed that the universe came into existence with a s...

Introduction to Natural Sciences Dr. Shwetha S Durgad Assistant Professor Christ Univeristy  Biochemical evolution Life appeared after a period of chemical reactions according to physical and chemical laws. It is presumed that the universe came into existence with a single titanic explosion called the “big bang” about 15000 million year ago. The fragments of the fireball expanded and cooled to give rise to many celestial bodies. The earth originated about 4.6 billion years ago. Earlier life was taught to be created from some super natural power.  Origin of life ❖ Origin of life on earth is called as protobiogenesis. ❖ It is clear that life came to existence from non-living substance or primordial earth about 3 billion years ago. ❖ There are many theories for the origin of life: Theory of special creation Cosmozoic theory Theory of spontaneous generation of abiogenesis theory Theory of biogenesis Modern self assembly theories  Theory of special creation According to this theory all the livings on earth are created by god or by some super natural power. Cosmozoic theory Life on earth came from different planet in the form of spores or microorganisms. This is called as cosmozoa or panspermia, which were preserved inside meteorites. These meteorites struck into a barren earth to release cosmozoa and help in development of various creature. Theory of spontaneous generation/theory of abiogenesis It is also a called auto biogenesis. Greek philosophers in 600BC Life originated from non-living thins spontaneously, without any interruption. Louis Pasteur and others disprove this theory and gave the scientific explanation that life originated only from the pre-existing life or biogenesis. Theory of Biogenesis Francisco redi, Spallanzani and louis Pasteur. This theory could not explain first life on earth but able to explain continuity of life. Living organisms are always produced from pre-existing living forms by reproduction and not from non-living or lifeless matter.- Spontaneous generation, a persistent idea  Modern self assembly theories Modern self assembly theory holds that protobiogenesis occurred due to inherent property of chemical molecules of self organization or self assembly. This theory include conversion of micro molecule into macro molecules to cell like microsystem. First demonstration was provided by Schmitt (1956) who has synthesized collagen from simple micro molecules. Reed (1967) demonstrated a inter macromolecular assembly by assembling two protein molecules which resulted into enzymatically active complexes. The accepted model of protobiogenesis suggested that information flowed from amino acid in geochemical matrix to protein in first organism. First life came into existence by combination of chemical compound by constant chemical reaction over long period of time. This is known as chemical evolution of life or self assembly theory of origin of life or biochemical origin of life or molecular evolution. This theory was formulated by Haeckel but developed by Oparin and Haldane.  Oparin theory of chemical evolution The Russian scientist Alexander Ivanovich Oparin (1924) - “Primeval soup Theory” Process of chemical evolution can be divided into three step. Step 1: Origin of earth and primitive atmosphere Step 2: Formation of ammonia, water and methane Step 3: Synthesis of simple organic compound: Step 1: Origin of earth and primitive atmosphere When earth was broken from sun, it was a glowing fire and a rotating cloud of hot gases, vapors of various elements, pieces of rocks and metals called nebulous. As earth was moving away from sun, the temperature slowly decreased. This led to condensation of gases. The heavy elements (iron, nickel) sank to the centre and form solid core of earth. Lightest elements (He, H, O, N, C) occupied atmosphere of the earth  Step 2: Formation of ammonia, water and methane The earth was very hot initially and so the atoms could not combine with each other easily. It contains H, O, N and C. Hydrogen was very reactive it combine with nitrogen to form ammonia, with oxygen to form water, with carbon to form methane. As temperature was high ammonia and methane remained as gas and water as steam As temperature decreased steam condensed to water which results in rain and earth become cold. Water gradually accumulated and this led to the formation of rivers, sea lakes etc. Thus the first chemicals formed on the earth were water, ammonia, methane etc.  Step 3: Synthesis of simple organic compound: Next step is formation of micro molecules. When temperature of earth gradually cooled down then the highly reactive free radicals CH and CH2 condensed to form variety of saturated and unsaturated hydrocarbon. Hydrocarbon, ammonia, water show condensation, polymerization, reduction and oxidation. This results into formation of various biologically active molecules like monosaccharides, amino acids, purines, pyrimidines, fatty acids and glycerol etc. Haldane theory of chemical evolution British scientist J.B.S Haldane (1929) described the sea containing molecules of organic substances in abundance as “ the hot dilute soup or primitive broth”. Process of chemical evolution can be divided into five / six step. Step 1: Formation of complex organic compounds Step 2: Formation of Nucleic acids Step 3: Formation of protobionts or precells Step 4: Formation of first cell Step 5: Biological evolution Step 1: Formation of complex organic compounds The hot dilute soup was sterile and oxygen free. Simple organic compound come together, form colloids to form complex compound like polysaccharides, proteins, nucleosides, fats and nucleotides. The protein molecules formed by polymerization of amino acids (protoprotein). The formation of protein molecules is considered as a land mark in the origin of life. Step 2: Formation of Nucleic acids Step 3: Formation of protobionts or precells: The nucleic acid along with inorganic and organic molecules formed the first form of life precells or protobionts. Proteins formed colloidal hydrophilic complexes surrounded by water molecules. Oparin and Sidney Fox demonastrated the formation of this aqueous suspension of polymers. Oparin called these aggregates as cocervates, while Sidney fox called them Protenoids or Microspheres. Step 4: Formation of first cell This was significant steps in transformation of precells into cells. Step 5: Biological evolution The first cell or primitive cells were marine and hetrotrophic in nature. Growth and multiplication of these cells caused depletion of food and increase in CO2 due to fermentation. This led to development of chromophores. This event help to transform heterotrops to autotrophs. Due to release of oxygen as a byproduct of photosynythesis, the primitive reducing atmosphere was slowly and gradually converted into oxidizing atmosphere Miller- urey experiment (or Urey-Miller experiment) The Miller- urey experiment (or Urey-Miller experiment) was an experiment that simulated the conditions thought at the time to be present on the early earth, and tested for occurrence of chemical origins of life. They specifically tested the theories of Alexander Oparin’s and J.B.S Haldanes hypothesis which emphasized that the conditions on the primitive earth favured chemical reactions that synthesized more complex organic compounds from simpler organic precursors. This experiment is considered to be classic experiment concerning the experimental abiogenesis, it was conducted in 1953, by Stanley Miller and Harold Urey at the university of Chicago and later the university of California, San Diego.  The chemicals (H2O, CH4, NH3 & H2) were sealed inside a sterile glass flask, and flasks wee connected in a loop, with one flask half- full of liquid water and another flask containing a pair of electrodes. The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.  Observation: Within a day, the mixture had turned pink in colour, and at the end of two weeks of continuous operation, miller and urey observed that as much as 10-15% of the carbon within the system was now in the organic compounds. Two percent of the carbon had formed amino acids that are used to make proteins, in living cells, with glycine as the most abundant. Sugars were also formed. Nucleic acids were not formed within the reaction. 18% of the methane-molecules became bio-molecules. The rest turned into hydrocarbons like bitumen. Summary: How did Life originated??? - Is it really originated??? The first 'modern' model for the origin of life was presented in the 1923 independently by the Russian biochemist A. I. Oparin and later supported by the British evolutionary biologist J. B. S. Haldane in 1928. The Oparin and Haldane theory is known as biochemical theory for the origin of life. Miller–Urey experiment Prebiotic earth Conditions of the primitive earth was not the same as those present today. No spontaneous generation of life today (pasteur), because the necessary conditions no longer exist. Abiogenesis: “Primeval soup theory”. “The hot dilute soup or primitive broth”. Pre RNA world : Organic compounds including glycine found… From monomers to polymers – Amino acids Polypeptides, could have occurred when dry or highly concentrated monomers are heated. Condensation reactions take place forming peptide bonds between amino acids or phosphodiester bonds form between nucleotides. Early Catalysts: As molecules absorb to the clay mineral particles they become concentrated (stick to the surface of clay particles). Clay particles (Cocaervates) may have been essential catalysts in the formation of polymers. RNA world The first polynucleotides: Polynucleotides show a tendency to copy themselves using complementary base pairing. This was probably catalyzes by the presence of clay particles and metal ions. These single stranded polynucleotides would have been the equivalent of RNA. The first hereditary information: RNA was probably the first hereditary molecule having the ability to copy itself. RNA shows enzymic (catalytic) properties – called ribozymes.Polynucleoties are very good molecules at storing and transmitting information but they lack the versatility for all the chemical functions of a cell. A great partnership: Polypepides can form complex 3- dimensional structures (proteins), Polypeptides much better at complex cell functions. A partnership must have formed between the polynucleotides and the polypeptides. The polynucleotides directed the synthesis of the polypeptides. Today it is clear that information only flows from polynucleotides to polypeptides. Translation had started. First DNA The origin of DNA: ❖ Hereditary information was probably stored in the form of DNA later, DNA is more stable than RNA. ❖ The passage of information from RNA to DNA is possible in nature. ❖ The reverse transcriptase enzyme of the retro viruses shows this. The first membranes, the first cells: ❖ If a piece of RNA codes for a particularly good protein then there is nothing to stop that protein being used by other RNA molecules. ❖ If, however, the RNA is enclosed in a membrane then it can keep its protein to itself and it gains a selective advantage. ❖ So membranes probably pushed evolution by natural selection forwards. Membranes defined the first cell: The phospholipids form lipid bilayers when they are surrounded by water. All the components of a simple prokaryotic cell were now assembled. They diversified in their metabolism. By 2 billion years age free oxygen was appearing in the atmosphere due to the activity of photosynthetic bacteria. Diversity of Life Origin of life  Introduction to Cell Dr. Shwetha S Durgad Assistant Professor Christ Univeristy Endosymbiosis theory of eukaryotic cell Curious fact: Carl Sagan was husband of Lynn Start of colony life- Emergence of multicellular organisms Unicellular organism to multicellular organisms Characteristics of Life Cell is a transient dynamic system Animal cell Cell division  Footprints in embryonic development Germ layers Division of labour in cells - formation of tissue Human body is made up of 1 trillion cells and every day about 300 billion cells are produced as well as die every day. About a 60000 cells are shed of from the skin alone. Structural organization of human body (cell to organ systems) Biochemical origin of life Dr Shwetha S Durgad Chemical reaction Why??? How???  Define a chemical reaction? A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), & can often be described by a chemical equation. Thus, chemical reaction a process that involves rearrangement of the molecular or ionic structure of a substance, as distinct from a change in physical form or a nuclear reaction. What happens during a chemical reaction ? No new atoms are created, & no atoms are destroyed. In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, & atoms rearrange & form new bonds to make the products. What do you understand by a chemical bond ? A chemical bond is a lasting attraction between atoms that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between atoms with opposite charges, or through the sharing of electrons as in the covalent bonds. What do you understand by symbols of chemical elements? The symbols of chemical elements are abbreviations used to denote them. The symbols of the elements given in the question are as follows: 1. Carbon – C: The symbol of carbon is the first letter of its name. 2. Calcium – Ca: The symbol of calcium is derived by taking first two letters from it name. 3. Copper – Cu: The symbol of copper is derived from its latin name (Cuprum). 4. Chlorine – Cl: The symbol of chlorine is taken from the first letter & the letter that we predominantly pronounce while reading its name. 5. Cobalt – Co: The symbol of cobalt is derived by taking first two letters from its name. 6. Hydrogen – H 7. Nickle – Ni 8. Magnesium – Mg 9. Oxygen – O 10. Ferrous (Iron) - Fe Chemical reactions Saturated Solution Definition: A saturated solution contains the maximum amount of salt (NaCl) that can be dissolved in water at a specific temperature. Characteristics: Any additional salt added will not dissolve and will remain as solid crystals at the bottom. The rate at which the salt dissolves is equal to the rate at which it crystallizes, resulting in a dynamic equilibrium. Example: If you add salt to a glass of water & stir, a point where no more salt will dissolve, & some salt will settle at the bottom. At this point, the solution is saturated. Unsaturated Solution Definition: An unsaturated solution contains less salt than the maximum amount that can be dissolved in water at a specific temperature. Characteristics: More salt can be dissolved in the solution until it reaches the saturation point. There is no precipitate in an unsaturated solution. Example: If you add a small amount of salt to a glass of water & stir, all the salt dissolves completely. This means the solution is unsaturated. Supersaturated Solution Definition: A supersaturated solution contains more salt than what can typically be dissolved in water at a specific temperature. Characteristics: Supersaturated solutions are unstable and can precipitate the excess salt if disturbed or if a seed crystal is added. They are usually prepared by dissolving the salt at a higher temperature and then slowly cooling the solution without disturbing it. Example: To create a supersaturated solution, you can heat water and dissolve a large amount of salt in it. Oh! You mean Hydrogen Bond aka H-bond!!! Amino acid Thank You