Lysosomes

Lysosomes are membrane bound vesicles that contain more than 40 hydrolytic enzymes that can digest most biological macromolecules. These organelles function vitally as the sites of intracellular digestion that are more numerous in cells performing phagocytosis. The restrictive membrane keeps the digestive enzymes separate from the cytoplasm. The most common lysosomal enzymes are acid phosphatase, ribonuclease, deoxyribonuclease, proteases, sulfatases, and lipases. The enzymes function the best at pH 5 and are mostly inactive at the pH of the cytosol. This taken with the limiting membrane allows the cell to not digest itself. Lysosomal enzymes are made on the rough ER, then transferred to the Golgi apparatus for modification and packaging. The cellular machinery attaches a directional signal to the enzymes that allows the ER and Golgi to sort these proteins and, then via a receptor mediated process, segregate them to form lysosomes.