Question

why lylosomes are called sucidial bags of cell

Answer 1

1 Lysosomes contain the destructive enzymes. 
2 thus the enzymes normally do not come in contact with the rest of the cell parts.
3 The materials that need to be destroyed are transported to lysosmes.
4 At time the lysosomes burst and the enzymes are released to digest the cell.

Answer 2

The lysosomes contain several digestive enzymes which when released bring about the breakdown of various cytoplasmic structures. If these enzymes are released freely in the cell, they would result in autodigestions of the cell itself.They digest the stored food during starvation.
Therefore, they are referred to as the suidide bags of the cell.