What is Lock and Key hypothesis or model

Lock and key hypothesis :

It was proposed by the Emit Fischer, it depend upon the fact that only the specific key can open on the specific lock in same

Manner specific enzymes can transfer only the specific substrate into the product.

 According to this model active site of enzymes have  

the rigid structure and no change or the flexibility in it before, during or after the enzyme action.

The active site of enzyme is rigid and preshaped template where only specific substrate can attach, model does not give any scope for the flexible nature of enzyme Hans the model totally failed to explain many facts of enzymatic reaction.

Some postulates :

1. The substrate is drawn on to the active site of enzyme

2. The substrate shape  must be compatible with the enzymes active site in order to fit and  reacted upon

3. The enzyme modifies the substrate in this instance the substrate is broken down releasing products