Lysosomal proteins are often degradative enzymes. How does the cell keep these enzymes from degrading non-lysosomal cellular components on their way to the lysosome? Solution Answer: Lysosome contains more than 40 types of hydrolytic enzymes which includes proteases, nucleases, glycosidases, lipases, phospholipases, phosphatases etc. All are acid hydrolases.These enzymes show optimal activity in acidic environment and the lysosome provides this environment by maintaining a pH of about 5.0 inside it. In this way, the contents of the cytosol are highly protected against attack by the cell\'s own digestive system. The membrane of the lysosome normally keeps the digestive enzymes seperated from cytosol, but in case they leak out, they can only do very little damage at the cytosolic pH of about 7.2. lysosomes are synthesised in the rough endoplasmic reticulum (RER) and transported through the Golgi apparatus to the trans Golgi network. The transport vesicles that deliver these proteins to late endosomes (which later form lysosomes) bud from the trans Golgi network. Enzymes that are destined for a lysosome , specifically tagged with the molecule Mannose 6-phosphate, so that they are properly sorted into acidified vesicles. The vesicles subsequently deliver their contents to a late endosome. By this mechanism cells keep these enzymes from degrading non-lysosomal cellular components on their way to the lysosome..