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Biological Molecules

  • Date Submitted: 05/18/2011 07:09 AM
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Biological Molecules

BIOCHEMISRTY

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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