Biochemistry is a branch of biology, which deals with the study of chemical components and chemical processes in living organisms.
WATER (H2O)
MAIN CHARACTERISTICS OF WATER
* Chemically it is “Dihydrogen oxide”
* It is the most abundant component in living cell.
* Its amount varies approximately from 70 to 90% and life activities occur in the cell due to the presence of water.
* It is a polar molecule, means that it has a very slightly negative end (the oxygen atom) and a very slightly positive end (the hydrogen atom).
* Due to its polarity, H2O molecules form hydrogen bonds.
IMPORTANT BIOLOGICAL PROPERTIES OF WATER
(1) BEST SOLVENT
* Water is an excellent solvent for polar substances, when ionic substances dissolved in water, dissociate into positive and negative ions.
* Non-ionic substances, having charged groups in their molecules, are dispersed in water.
* Because of solvent property of water, almost all reactions in cells occur in aqueous media.
(2) HIGH HEAT CAPACITY
* Water has great ability of absorbing heat due to its high specific heat capacity.
* The specific heat capacity of water is the number of calories required to raise the temperature of 1g water through 1ºC.
* The thermal stability plays an important role in water based protoplasm of individual’s metabolic activities.
(3) HIGH HEAT OF VAPORIZATION
* Liquid water requires higher amount of heat energy to change into vapours due to hydrogen bonding which holds the water molecules together.
* It provides cooling effect to plants when water is transpired, or to animals when water is respired.
(4) ACT AS AMPHOTERIC MOLECULE
* Water molecule acts both as acid and a base. As acid, it gives up electron to form H+ ion, while as a base, it gains electron to form OH ions.
H2O ↔ H+ + OH-
* It acts as buffer and prevents changes in the pH of living body.
(5) PROTECTION
* Water is an effective lubricant...
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