BIOCHEMICAL PROPERTIES OF WATER .Raveesh.pptx

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1. KUVEMPU UNIVERSITY Sahyadri Science College, Shivamogga PG Department of Biotechnology SEMINAR TOPIC ON BIOCHEMICAL PROPERTIES OF WATER PRESENTED BY: Mr. Raveesha D 1 st Msc (1 st semester) Sahyadri science college Shivamogga UNDER THE GUIDANCE OF Dr. Pradeepa k Assistant Professor PG dept of biotechnology Sahyadri science college Shivamogga

2. contents Introduction Structure Biochemical properties of water Polarity of water Amphiprotic nature of water Anomalous behaviour of water Ionization of water P h Buffer conclusion

3. introduction Water is composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. The strucutre of the water molecule gives water its unique properties. These properties include its high polarity, solvent, cohesive, adhesive properties, high specific heat capacity, and its ability to ionize. These charateristics make water a universal solvent, facilitating biochemical reactions, maintaining cellular structures, and regulating temperature in living organisms. Each molecule of water consists of one atom of oxygen and two atoms of hydrogen, so it has the chemical formula H₂O.

4. Structure of water molecule Water consists of one atom of oxygen and two atoms of hydrogen which are held together by covalent bond, which is formed by sharing of 2 electrons. These bonds are formed because of higher electronegativity of oxygen atom. The oxygen atom attracts the shared pair of electrons of the covalent bonds towards itself than hydrogen atom. Has a result it has a region with a slight negative charge (the oxygen atom) and a region with a slight positive charge (the hydrogen atoms). The bond length between hydrogen and oxygen is 95.84 pm. It has bond angle 104.45’, with a bent shape.

5. biochemical Properties of water Solvent property : Water is the universal solvent most of biological activities and chemical reactions occur in aqueous (water- based) solutions. It is a polar molecule with partially positive and negative charges, it readily dissolves small non polar covalent molecules, ionic compounds, and other polar covalent molecules . Water soluble molecules are described as hydrophilic (water loving). Hydrophilic molecules dissolve in water. Those molecules that are not soluble in water are hydrophobic (water hating or fearing). Hydrophobic molecules repel water. Medium for chemical reactions- hydration/dehydration reactions.

6. Water in reactions When the ionic compounds are added to water, individual ions interact with the polar regions of water molecules during dissociation. Ex; Nacl crystals are added to water, it dissociates into Na+ and Cl - ions and the positively-charged sodium ion is surrounded by the partially - negative charge of the water molecule oxygen, the negatively-changed chloride ion is surrounded by the partially- positive charge of the hydrogen in the water molecule .

7. Polarity of water Water is polar molecule because oxygen and hydrogen have different electronegativity value. Here oxygen attracts shared pair of electrons towards itself than hydrogen atom. It forms polar covalent bonds. This creates a partial positive charge on hydrogen and a partial negative charge on oxygen atom. Water has a variety of unusual properties because of attractions between these polar molecules. The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond which is a weak bond. Water molecules attract each other through the special type of dipole-dipole interaction known as hydrogen bonding.

8. Amphiprotic nature of water Due to its highly polar structure, water can either act as an acid (by donating a proton to a base) or a base (by using a lone pair of electrons to accept a proton). As bases : When a strong acid like Hcl dissolves in water, it separates into chloride ions (Cl – ) and protons (H+). In turn, the proton reacts with a water molecule to form the hydronium ion (H 3 O + ). Hcl ( aq ) + H 2 O(l) → H 3 O + ( aq ) + Cl – ( aq ) The acid in this reaction is Hcl , and the base is water, which accepts an H + ion. As acids : Water can also act as an acid. H 2 O donates a proton to NH 3 , which acts as a base. In this equilibrium reaction:H 2 O( aq ) + NH 3 ( aq ) ⇆ (NH 4 ) + OH - Water is thus called amphiprotic because it can act as an acid or a base depending on the nature of the other reactant.

9. Anomalous behaviour of water . It is a abnormal property of water where by it expands instead of contracting when temperature goes from 4 degree Celsius to zero degree Celsius and it became less dense. Example : the density of ice is lower than water, so it floats on water. At about 4 degree Celsius water reaches its maximum density ,behind its temperature water will always expand whether it is being warmed up or cooled down . This characteristics of water plays significant role in sustaining marine life.

10. Cohesion -water molecules stick to each other which are held together by hydrogen bonds. Adhesion- water molecules stick to unlike surfaces such as glass or plastic due to hydrogen-bonds between water and other polar compounds. Surface tension -the property of the surface of liquid(water) that allows it to resist an external force due to the cohesive nature of its molecules. High specific heat- it takes a lot of energy to raise or lower the temperature of water. As a result, water plays a very important role in temperature regulation. High heat of vaporization- many hydrogen bonds must be broken before water can evaporate so it needs high heat.

11. Ionization of water The water molecule ionizes to form H + and OH - ions. The reaction in which a water molecule donates one of its protons to a neighboring water molecule, either in pure water or in an aqueous solution, is called the self-ionization of water. In an self ionization process, one water molecule can react with another to form an OH – ion and an H 3 O +  ion:

12. P h P H =potential of hydrogen, (negative log of the concentration of hydrogen ions). water ionizes, H + splits off from H₂O, leaving OH - If [H +] = [OH - ], water is neutral. Ph = 7. If [H + ] > [OH - ], water is acidic. Ph<7. If [H + ] < [OH - ], water is basic. Ph>7. P H scale measures the acidity or basicity of aqueous or other liquid solutions.

13. buffers Buffers are aqueous systems that resist Changes in P H when small amounts of a strong acid or base are added. Types of buffer solutions Acidic buffers :- These solutions are used to maintain acidic environments. Acidic buffer has acidic P H and is prepared by mixing a weak acid and its salt with strong base. The P H of this solution is below 7. Ex : Sodium acetate and Acetic acid.(P H 4.75). Alkaline buffers:- these buffer solutions are used to maintain basic conditions it is prepared by mixing week base and its salt with strong acid. P H of these solution is above 7. Ex: Ammonium hydroxide and Ammonium chloride (P H 9.25). • Control P H by buffers , reservoir of H + Donate H + when [H + ] falls, Absorb H + when [H + ] rises.

14. conclusion Water is an excellent solvent it has Unique ability to dissolve many polar and ionic substances it has unusual properties resulting from the water molecules polar structure that give rise to hydrogen bond. The biochemical properties of water play vital roles in various biological processes, including solvent action, temperature regulation, and participation in metabolic reactions. Its unique properties, such as high specific heat, cohesion, and universal solvent ability, make it indispensable for life as we know it. Further more, water's cohesive properties enable it to form hydrogen bonds.

15. reference Fundamentals of biochemistry, Dr. JL Jain, Dr. Sunjay Jain, Nithin Jain. S chand publications. Page no: 2-30. Biochemistry, SC Rostogi , Tata MC Grew hill publications. http:// biolibretexts.Org /courses—biochemical propreties of water.