1. Properties of WATER | Biochemistry | Notes and Practice Questions in description

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Complete Notes and Practice Question

A water molecule has 2 hydrogen atoms covalently bonded to one oxygen atom.
 Water is a bent molecule
o Its bent because of the 2 lone pair electrons present on the oxygen atom
 Water is a polar molecule
o It’s polar due to the presence of oxygen which is highly electronegative. Oxygen attracts the covalently bonded electrons and gets a partial negative charge and hydrogen gets a partial positive charge, leading to the formation of a dipole.
 Water forms intermolecular hydrogen bonds
o Due to partial +ve charge on hydrogen and partial -ve charge on oxygen
o This large difference in charge between hydrogen and oxygen cause force of attraction to act between them (opposite charges) and these forces of attraction are known by a special name “Hydrogen bonds”.
o Hydrogen bonds are not bonds actually they are interactions happening between two atoms with partial opposite charge.
o Similar interactions are also seen when hydrogen bonds with nitrogen and fluorine as both of these are highly electronegative.
 Ionic compounds dissolve in water because of interaction between anion and hydrogen atom or cation and oxygen atom
 Polar compounds dissolve in water as they have dipole-dipole interactions (Hydrogen bonds)
 Polar molecules are hydrophilic and non-polar molecules are hydrophobic.
 Ionic compounds are extremely polar and hence they are hydrophilic
 Non-polar compounds don’t dissolve in water as water is busy interacting with its own molecule by hydrogen bonds and hence these are called hydrophobic.
 As the number of polar groups increases in a compound the solubility of that compound in water increases.
 Certain compounds have both polar and non-polar regions in their structure and these are called amphipathic compounds. Eg. Soap molecule and phospholipids (present in the plasma membrane)

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