. [ 1 [[ http://en.wikipedia.org/wiki/Lysosome#cite_note-0 |]]] At pH 4.8, the interior of the lysosomes is more acidic than the cytosol (pH 7.2). The lysosome's single membrane stabilizes the low pH by pumping in protons (H+) from the cytosol via proton pumps and chloride ion channels . The membrane also protects the