Lysosomes are membrane-bound organelles in a cell. A lysosome contains digestive enzymes, which are known as hydrolytic enzymes. This organelle functions to digest and remove waste materials. It plays a huge role in cell programmed death, known as apoptosis. Lysosomes are also helpful in destroying foreign bodies like viruses and bacteria. When a cell is damaged, it is moved to the lysosome, the lysosome opens up and engulfs of the damaged cell. Once inside the lysosome, the digestive enzyme begins to break down the damaged material. For the hydrolytic enzymes to work, they require an acidic (low PH) environment to function. After breaking down the material, the lysosomes expel the remains into a cell in the form of a vesicle. The vesicle is expelled from the cell through the cell membrane.