lysosomes and peroxisomes

1. Lysosomes Dr.Sujit Ghosh

2. Introduction Lysosomes have been classically considered terminal degradative organelles, but in recent years they have been found to participate in many other cellular processes, including killing of intracellular pathogens, antigen presentation, plasma membrane repair, cell adhesion and migration, tumor invasion and metastasis, apoptotic cell death, metabolic signaling and gene regulation. In addition, lysosome dysfunction has been shown to underlie not only rare lysosome storage disorders but also more common diseases, such as cancer and neurodegeneration. 

3. An infected cell a pathogen is further challenged by intracellular defense Mechanisms. Prominent among these is the fusion of pathogen-containing vacuoles With lysosomal compartments. Activated-macrophages and dendritic cells, for example, provide the least hospitable environment while non-immune cells are more permissive. To avoid lysosomal fusion, a pathogen could potentially escape the membrane-bound vacuole. However, nod-like receptors (nlrs) and rig-like receptors (rlrs), recognize pathogen associated molecular patterns (pamps) in the cytoplasm and induce the production of proinflammatory cytokines and chemokines. These molecules influence adaptive immune response and can trigger host cell death via activation of the inflammasome , Additional antimicrobial responses include autophagosome formation on the surface of cytoplasm-exposed bacteria and their eventual fusion with lysosomes. Some pathogens like listeria and shigella have specifically adapted to life in the host cell cytoplasm by engaging in actin-based motility and by suppressing induction of autophagy

13. Peroxisome is shaped like a sphere and can be found in the Cytoplasm of a cell. It has a single membrane inside. The Lipid bi-layer separates the inside of peroxisome from the outer layer. 100-500nm in diameter A lipid bilayer surrounds the crystalline core Dense matrix present the inside of the core