Lysosomes    

Lysosomes have  a  single  boundary membrane and it is are  found  only  in  animal  cells,. The internal pH of these organelles is mildly acidic (pH 4-5), and is maintained by integral membrane proteins which pump H ions into them. The lysosomes have a range of hydrolases that are optimally active at this acidic pH (and therefore are termed acid hydrolases)  but which are inactive at  the  neutral  pH  of  the  cytosol  and  extracellular  fluid.  These enzymes are involved in the degradation of host and foreign macromolecules into their monomeric subunits; lipases degrade lipids, proteases degrade proteins, phosphatases remove phosphate groups from phospholipids and nucleotides, and nucleases degrade RNA and DNA. In the degradation of extracellular  macromolecules Lysosomes  are involved  that have been brought into the cell by endocytosis  as  well  as  in  the  degradation   and  recycling  of  normal cellular components.