TAMU BIOL 454 Questions and Answers correct

TAMU BIOL 454 Questions and Answers correct Endocytosis Substances are brought into cell & surrounded by a membrane Pinocytosis Performed by any eukaryotic cell (takes in fluids, cellular drinking) Phagocytosis ONLY SPECIALIZED cells can perform-takes in large particles Upon entry of a microorganism the phagocytic cells must: -find it -bind it -ingest it -digest it -present it Extravasation Cells leaving circulation to enter tissues to travel to site of infection/injury (following a chemical gradient) Find it -Extravasation -normally blood cells move rapidly down the center of the vessel -cells make their way to this site by CHEMOTAXIS Bind it -At infection site, phagocytes adhere to the microbes -Microbes try to counteract this step by the presence of a capsule -Opsonization Opsonization Host counteracts presence of the capsule by COATING the microbe with Abs or proteins of the complement system (enhances process of phagocytosis) Directly interact with pathogen surface? Mannose receptor, Dectin-1, scavenger receptors, lipid receptors How do macrophages bind to pathogen? Via opsonin (already bound to pathogen) Ingest it - Opsonization allows engulfment by phagocytes - Pseudopodia - Phagosome Pseudopodia Cell membrane of the phagocyte forms finger like extensions Phagosome Pseudopodia then fuse enclosing the microbe within a VACUOLE Digest it -Lysosome -Phagolysosome -Enzymes and toxic O2 byproducts kill and breakdown the microbe -Once the microbe has been digested= peptides (+ MHCII) and indigestible material (in residual body- cell membrane) Lysosome The Phagosome fuses with other organelles in the cytoplasm (bag of enzymes and other mediators) Phagolysosome Fused vacuole Oxygen dependent killing mechanism - Pathogen activated phagocytic cell Respiratory burse Oxygen dependent killing mechanism - activated membrane bound oxidase= NADPH oxidase complex - superoxide anion (O2-) O2- also generates other toxic O2 components (ROS) Oxygen dependent killing mechanism - ROS (reactive O2 species) • destroy CM - destroy cell • can also irreversibly damage proteins and DNA - influx in hydrogen ions - to neutralize superoxide anion (O2-) Oxygen dependent killing mechanism - acidic pH is also deleterious = activated hydrolytic enzymes (causes damage) The NADPH oxidase enzyme is composed of a number of different subunits 1) Inactive until assembled 2) Phagocytosis stimulates assembly process 3) GTPase activates assembled exnzyme complex 4) Some components are in the endosomal membrane and some are in the cytosol Class of mechanism (Oxygen dependent mechanism) - Acidification - Toxic oxygen-derived products (ROS) - Toxic nitrogen oxides (RNS)