Lysosome is an organelle whose function is related to digestion within the cell(intracellular digestion)so it has 40 digestive enzymes or hydrolysing enzymes in it. When foreign materials enter in the cell it digests that material. But when the cell is old and function well,it is digested by lysosome releasing hydrolysing enzymes. It finishes its own existence by killing its own cell. So it is called " bag of suicide"or suicidal sac