Primary lysosomes are small concentrated sacs of enzymes that are not digesting anything. Primary lysosomes fuse with a phagocytic vacuole to become secondary lysosomes or phagolysosomes where digestion begins. As the substances are digested the nutrients diffuse through the lysosomal membrane to the cytosol. Residual bodies are formed when indigestable things remain in the vacuoles. In cells with a long life span such as cardiac muscle cells, residual bodies are more numerous and are referred to lipofuscin or age pigment.
Lysosomes also participate in the turnover of cellular organelles.
Cytoplasmic components become enclosed in a membrane that fuses with a primary lysosome to become an autophagosome. In bone, the lysosomal enzymes are released from osteoclasts to digest surrounding bone during the process of remodeling. Lysosomal enzymes are also involved in the process of inflammation . Peroxisomes contain amino oxidases, hydroxyacid oxidase and catalase. Catalase protects the cell from hydrogen peroxide damage.