Importance of hydrogen bonding in biological system.

What is hydrogen bonding ?

When a proton donor group interacts with an electron donor having a lone pair of electrons or a pi bond, a weak bond is formed represented by dotted line, known as hydrogen bonding. 

There are two types of hydrogen bonds.(I)Inter-molecular hydrogen bond and (II) Intra-molecular hydrogen bond which are shown below.

 Importance of hydrogen bonding in biological system.

Both intra-molecular and inter-molecular hydrogen bonding has a important role in biological system.

The long helical structure of protein molecules and double helical structure of DNA molecules are stabilised by the existence of H-bonding .

For example, a protein molecule contains a large number of  >C= O and  >N一H groups and hydrogen bonding occurs between these two groups are as follows.

A single protein molecule contains a large number of these hydrogen bonds.Although each of them is very weak yet the overall effect of all the hydrogen bonds is highly significant and brings stability to the molecule of protein.

The hydrogen bonding force in protein and cellulose makes them able to absorb dyes.



Summary


What is hydrogen bonding? 
importance of hydrogen bonding in biological system.

What is VSEPR theory?