micro 020 LAB EXAM #1 QUESTIONS WITH CORRECT DETAILED ANSWERS SUCCESS GUARANTEED.

Aseptic technique includes... (a) sterilization of transfer tools before and after use (b) disinfection of bench tops (c) washing hands (d) all of the above - correct answers(d) all of the above Placing the cap of a broth cultures up on the bench top is acceptable True/False? - correct answers False Why is it important to allow the inoculating loop to cool prior to obtaining the inoculum? - correct answers to avoid frying the cell A pure culture can be prepared from a mixed broth or a mixed agar slant culture directly True/False - correct answers False Which of the following is a benefit of using the streak plate method for obtaining isolated colonies compared to the pour plate method? (a) the streak plate method allows you to observe colonies on the surface and deep in the agar (b) the pour plate method does not require serial dilutions (c) the streak plate method requires serial dilutions (d) the streak plate method does not require serial dilutions - correct answers(d) the streak plate method does not require serial dilutions When preparing a streak plate, it is important to only flame the loop before collecting a bacterial sample, not for every subsequent streak True / False? - correct answersFalse What is a bacterial colony? - correct answersa collection of bacterial cells that arose from a single cell Why is the use of oil immersion important when the 100x objective lens is in place? - correct answersit allows more light rays to enter directly into the objective lens to produce a clearer image Which part of the microscope magnifies the specimen at various magnifications? - correct answersobjective lens The ability to distinguish between two distinct points, which determines clarity of an image, is known as... - correct answersresolving power What property of the microscopes used in lab allows us to maintain coarse focus at 400x total magnification after having obtained focus a the lowest power objective? - correct answersparfocal When looking through the ocular lens, you will see... - correct answersthe field of views Which of the following is/are important when preparing a bacterial smear? (a) thin smears (b) complete air-drying prior to heat fixation (c) cleaning slides (d) all of the above - correct answersall of the above Mesophiles have an optimum growth temperature at around... (a) 25 C (b) 37 C (c) 60 C (d) 100 C - correct answers(b) 37 C Bacterial that are incubated below their optimum growth temperature would... - correct answersexhibit decreased growth rates Organisms that will only grow at temperatures above 50 C are classified as... - correct answersobligate thermophiles Which part of the following buffer systems is more likely to act like a weak base? (a) K2HPO4 (b) KH2PO4 (c) H+ (d) OH- - correct answers(a) K2HPO4 Proteins can act as natural buffers because of their amphoteric nature True/False - correct answersTrue The carboxyl end (-COOH) of amino acids are more likely to act like... (a) a weak base (b) a weak acid (c) a strong base (d) none of the above - correct answers(b) a weak acid Why is it important to incorporate buffers into media in which microorganisms are grown? (a) to prevent drastic changes in pH from acidic waste products (b) to prevent drastic changes in pH from basic waste products (c) to remove waste products and protect the microorganisms (d) a & b - correct answers(d) a & b When a bacterium is considered an aerotolerant anaerobe... (a) it preferentially grows in oxygen, but can also grow in the absence of oxygen (b) it does not use oxygen for growth, but is not harmed by the presence of oxygen (c) it can only grow in the absence of oxygen (d) it requires limited amounts of oxygen - correct answers(b) it does not use oxygen for growth, but is not harmed by the presence of oxygen Which medium did we use to determine oxygen requirements for microbial growth? - correct answers(c) fluid thioglycollate medium When a substrate is oxidized, it _____ electrons and _____ hydrogens. - correct answersloses; loses How does the GasPak provide an anaerobic environment to grow bacterial cultures? (a) H2 is added to the environment in the presence of palladium pellets to remove O2 and form H2O (b) CO2 is produced from the gas generator envelope and absorbs excess O2 (c) palladium is activated and actively converts O2 to CO2 (d) a candle is lit to consume all of the available oxygen - correct answers(a) H2 is added to the environment in the presence of palladium pellets to remove O2 and form H2O Which of the following steps would you have to perform prior to staining bacterial cells? (a) stain the cells in the broth cultures (b) prepare a bacterial smear (c) boil the cells to sterilize the broth culture (d) submerge the cells in 7.5% saline to allow swelling of the cells - correct answers(b) prepare a bacterial smear Why is the heat fixation step important? (a) to kill the cells (b) to adhere the cells to the slide (c) to allow greater staining (d) a & b - correct answers(d) a & b When the background is dark and the cells are unstained, this staining preparation is known as... - correct answersnegative staining When preparing a simple stain... - correct answersany basic stain can be used Which of the following is/are characteristics of differential staining? (a) the staining process includes multiple staining reagents (b) the staining process allows us to distinguish between cell types (c) the staining process allows us to distinguish between cellular structures (d) all of the above - correct answers(d) all of the above Basic stains are more effective than acidic stains for staining bacteria because... - correct answers(a) basic stains have positively charged chromogens that are attracted by cell surfaces What special stain is used to identify acid-fast bacteria as it is soluble in the lipoidal materials that constitute most of the mycobacterial cell wall? - correct answerscarbol fuchsin If you were given a fresh culture (after 24 hours of incubation) and an older culture (after 1 week of incubation), which culture should you use for the spore stain? (a) the fresh culture (b) the older culture (c) both cultures are good to use (d) neither culture - correct answers(b) the older culture Using gram staining, gram ____ bacteria would stain pink, while gram _____ bacteria would stain purple. - correct answersnegative; positive