Lysosomes are speciallised cell organelles present in the cytoplasm. These common in animal cells but are also found in plant cells. It is surrounded by a single umit membrane, which encloses a dense stroma and a large vacuole, which contains about 50 hydrolytic enzymes. These enzymes can digest most of the biological substances. Lysosomes exist in four forms, such as primary lysosomes, secondary lysosomes, residual bodies and autophagosomes.