Water makes up 50-95% of living organisms and 56% of humans. Two-thirds of the body's water is intracellular fluid containing mainly potassium, magnesium, and phosphate, while one-third is extracellular fluid containing mainly sodium, chloride, and bicarbonate. The water molecule consists of two hydrogen atoms bonded to one oxygen atom, with the oxygen carrying a partial negative charge and hydrogens carrying a partial positive charge, giving water strong polarity and allowing it to be a universal solvent.

1. WaterWater
**Forms from 50% to 95% of the body of the organismsForms from 50% to 95% of the body of the organisms
**Forms about 56% of the body of the adult humansForms about 56% of the body of the adult humans
**2/32/3of it is found in the forms of intracellular fluids whichof it is found in the forms of intracellular fluids which
contain mainly K, M, Pocontain mainly K, M, Po44 and 1/3 of it is found in the form ofand 1/3 of it is found in the form of
extra cellular fluids contain mainly Na, Cl, HCOextra cellular fluids contain mainly Na, Cl, HCO33

2. Structure of WaterStructure of Water
**The water molecule consists of 2 hydrogen atoms and oneThe water molecule consists of 2 hydrogen atoms and one
oxygen atom. Each hydrogen atom is linked to the oxygenoxygen atom. Each hydrogen atom is linked to the oxygen
atom by a covalent bondatom by a covalent bond
**Oxygen carries partial negative charge but hydrogen carriesOxygen carries partial negative charge but hydrogen carries
partial positive chargepartial positive charge
**Water is a strong dipole and it is the universal and idealWater is a strong dipole and it is the universal and ideal
biological solventbiological solvent

3. Non covalent bondNon covalent bond
**Hydrogen bond:Hydrogen bond: formed by sharing of hydrogen atomformed by sharing of hydrogen atom
between hydrogen donor and hydrogen acceptor and is usedbetween hydrogen donor and hydrogen acceptor and is used
to determine: 1- viscosityto determine: 1- viscosity
22--surface tensionsurface tension
33--boiling pointboiling point
**Ionic bond:Ionic bond: formed between oppositely charged groupsformed between oppositely charged groups
**Vander wall forces:Vander wall forces: formed between transial dipoleformed between transial dipole
**Hydrophobic interaction:Hydrophobic interaction: formed between non-polar groupsformed between non-polar groups