Micro 3050 Midterm EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED

Micro 3050 Midterm EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED Leave the first rating Terms in this set (61) Function of the Ocula eyepiece, magnification 10 x Function of the Objectives the three lenses that help to increase magnification - 10 x, 40 x, and 100 x Function of the Course adjusting knobs bringing objects into focus Function of the Fine adjusting knobs bringing objects into focus at higher objectives Function of the Stage adjustment knobs moves stage up and down to bring an image into focus Know how to use the microscope (adjusting for proper viewing, getting an image in focus, using oil immersion) and how to take care of a microscope. a. On lowest magnification - use course knobs to get image in view. This may entail raising or lowering the stage, moving the slide forward/backward or side to side, or opening the light more b. Once focused at the lowest level, then can increase the focus and use the fine adjustment know to focus more c. Can add oil and go right up to 1000 x magnification and it will increase the resolving power (clarity) d. Once all done, clean the lenses with the appropriate paper provided - always clean lenses before and after use Describe aseptic technique and understand why it is important. a. When getting a sample: flame oculating loop, open vial and flame top of that, stick loop into tube and then bring out. Flame tube again and then flame loop - stay in radius of the flame to limit cross contamination b. This technique is important because it limits cross contamination and assists the student in getting the most pure culture possible Compare and contrast how to make a bacterial smear from liquid media and solid media. a. Liquid Media: using aseptic technique - just put a loopful of bacteria onto the slide - let air dry after applying b. Solid bacteria - add a drop of water onto the slide and then add the bacteria - let air dry Explain the importance of heat fixing and air-drying specimens on slides. a. Heat fixing - kills the bacteria and allows for them to stay stationary to be able to observe them and stain b. Air drying - if heat fix before air drying, the bacteria will boil and the cell morphology will be lost Distinguish between acidic and basic dyes and when to use each. a. A basic dye has a positive charge and will bind to negatively charged organisms which is why it is perfect to dye bacteria with basic dyes b. Acidic dyes have a negatively charged and bind to positive organisms/cells which is why it is frequently used in staining animal cells (histology) Describe simple staining and what bacterial characteristics can be observed using this technique. This is the use of a single stain to identify an organism by making internal or external structures more visible by contrasting them with the background Characteristics seen in a simple stain i. Pleomorphism: irregular form ii. Palisade arrangement: parallel arrangement of rod shaped cells iii. Metachromatic granules: granules within a cell seen when simple stained Recognize the different bacterial morphologies. a. Cocci - sphere shaped i. Diplo and tetrads - two and four groups ii. Strept - chains iii. Staph - clusters b. Bacilli - rod shaped i. Vibrios - comma shaped ii. Spirilla - rigid iii. Spirochetes - flexible Understand the distribution of bacteria in our world. Found everywhere and are most abundant organisms in the world Compare and contrast gram-positive and gram-negative cells (what colors they stain using the Gram stain and how cell wall structure determines how they stain). a. Gram positive - stains purple because of the large layer of peptidoglycan b. Gram negative - stains pink because of thin layer of peptidoglycan and outer membrane Know all of the steps and stains used in a Gram stain. Know the purpose of each stain and how bacteria look at each step. Know which stain is the primary stain, counterstain, mordant, and decolorizing agent. a. Primary stain - crystal violet; on for 20 seconds i. All cells will appear purple ii. Wash with water afterwards b. Mordant - iodine; on for one minute i. Makes complexes with violet to make larger complexes ii. All cells still purple c. Decolorizer - ethanol; wash until flow is colorless i. Gets the violet out of cells that don't have a lot of peptidoglycan ii. Some cells colorless and others remain purple iii. Wash with water after d. Counterstain - safranin; on for 1 minute i. Stains the colorless cells pink, other cells are purple ii. wash after and blot dry Understand the purpose of a streak plate and how you would do one. a. Purpose: dilute cells to be able to get an isolated pure colony from a pure culture b. Done by streak plate technique to get one cell that divides to form a colony Define pure culture and pure colony. a. Pure culture: only a single kind of an organism b. Pure colony: formed from a single cell and can be used to further study that specific organism from the single cell