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à Water is the basis of life on our planet, it exists in different physical states (solid, liquid, gas). Water makes up:-
à 70% of the surface of earth
à (65% - 90%) of the weight of living organisms
The importance of water
It plays an important role in all vital processes within living organisms.
The molecular structure of water
àwater molecule H2O is composed of one oxygen atom and two hydrogen ones, these atoms are bound covalently (by covalent bond).
àIn water molecule, hydrogen carries molecular negative charge, while oxygen carries molecular positive charge. Thus, water molecule is polar molecule because it has positive and negative poles.
Fig. (10) The molecular structure of water
à Close water molecules are attracted to each other by relatively low electric attraction (as negative hydrogen atoms attract positive oxygen atoms in another molecules). This bond is called Hydrogen bond
Fig. (11) Hydrogen bond diagram
à Water has unique properties because of its polarity and hydrogen bonds between its molecules
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| Proteins play an important role in life. | | | Water molecules are polar |