Lysosomes - They destroy foreign materials like bacteria and virus which enters the cell and thus protects the cell from infection. They also remove the old, defective and worn out parts of the cell by digesting them. During breakdown of cell structure, when the cell gets damaged, lysosomes may burst and digest the entire cell, hence they are also known as suicide bags of the cell.
Mitochondria - Mitochondria are sites of cellular respiration. They are known as the powerhouses of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP molecules.