BIOS 242 - Final Review Questions And Answers

BIOS 242 - Final Review Questions And Answers Three Domains - ANS Archaea, Bacteria, Eukarya Hierarchy - ANS Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species Zone of inhibition - ANS The clear region around the paper disc saturated with an antimicrobial agent on the agar surface. The clear region is an indication of the absence, or the effective inhibition, of microbial growth by the antimicrobial agent. Koch's Postulates - ANS 1. The suspected causative agent must be found in every case of the disease and be absent from healthy hosts. 2. The agent must be isolated and grown outside the host. 3. When the agent is introduced to a healthy, susceptible host, the host must get the disease. 4. The same agent must be found in the diseased experimental host. Scientists follow these basic principles when they try to identify the cause of an infectious disease. SEM Microscopy - ANS For this microscope, electrons don't pass through the specimen, but focus back and forth across the surface. Gives 3D images TEM Microscopy - ANS For this microscope, electrons passing through the specimen create image on a fluorescent screen. Bright Field Microscopy - ANS For this microscope, the background is illuminated. The light rays pass through the specimen into objective lens Dark Field Microscopy - ANS For this microscope, the light rays scattered by specimen enter the objective lens. The specimen appears light against a dark background Polarized Microscopy - ANS This microscope is built like regular optical microscope. Unlike regular microscopes which use normal light, this one uses polarized light to study specimens. Gram Stain components - ANS Primary stain (Crystal violet, methyl violet or Gentian violet) Mordant (Gram's Iodine) Decolourizer (ethyl alcohol, acetone or 1:1 ethanol-acetone mixture) Counterstain (Dilute carbol fuchsin, safranin or neutral red) Characteristics of Enzymes - ANS 1. Have a high molecular weight 2. Has an amphoteric nature - capable of ionizing either as an acid or as a base depending upon the acidity of the external solution. 3. They are colloid in nature due to which they present a large surface area for reactions to take place. 4. Enzymes are highly specific in