Exam 1 Chapter 3 Observing Microorganisms Through a Microscope

1) Which of the following is NOT equal to 1 mm?

D) 100 μm

2) What structure does light pass through after leaving the condenser in a compound light microscope?

C) specimen

3) Which of the following pairs is mismatched?

D) basic dye — negative stain

4) Which of the following places the steps of the Gram stain in the correct order?

1-Alcohol-acetone

2-Crystal violet

3-Safranin

4-Iodine

C) 2-4-1-3

5) Which of the following pairs is mismatched?

C) safranin — acid dye

6) Which of the following is NOT true regarding the acid-fast stain?

C) If cells are acid-fast, they are gram-negative.

7) The purpose of a mordant in the Gram stain is to

D) prevent the crystal violet from leaving the cells.

8) Which of the following places the steps in the correct sequence?

1-Staining

2-Making a smear

3-Fixing

C) 2-3-1

9) The negative stain is used to

D) visualize capsules.

10) Simple staining is often necessary to improve contrast in which microscope?

A) compound light microscope

11) Which microscope is used to see internal structures of cells in a natural state?

B) phase-contrast microscope

12) Which microscope uses visible light?

B) differential interference contrast microscope

13) Which microscope achieves the highest magnification and greatest resolution?

E) electron microscope

14) In using this microscope, the observer does NOT look directly at an image through a lens.

E) electron microscope

15) This microscope produces an image of a light cell against a dark background; internal structures are NOT visible.

C) darkfield microscope

16) A virus measures 100 nm in length. What is its length in μm?

C) .1 μm

17) Which of the following is NOT useful for observing living cells?

D) scanning electron microscope

18) A microorganism measures 5 μm in length. Its length in mm would be

E) 0.005 mm.

19) Which of the following correctly traces the path of light through the compound microscope?

A) light source; condenser; specimen; objective lens; ocular lens

21) Which microscope can be used to visualize DNA or botulinum toxin?

C) scanning tunneling microscope

22) Which microscope is used to observe a specimen that emits light when illuminated with an ultraviolet light?

D) fluorescence microscope

23) Which microscope is most useful for visualizing a biofilm?

D) scanning acoustic microscope

24) Which microscope takes advantage of differences in the refractive indexes of cell structures?

B) phase-contrast microscope

25) You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the first dye. What is the appearance of the bacteria at this point?

A) purple

26) You are performing a Gram stain on gram-negative bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point?

A) purple

27) You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point?

C) colorless

28) You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the counterstain. What is the appearance of the bacteria at this point?

A) purple

29) Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection?

C) Gram stain

30) Which of the following pairs is mismatched?

C) fluorescence microscope —uses a fluorescent light

31) What is the total magnification of a specimen viewed with a 10x ocular lens and a 45x objective lens?

E) 450x

32) You are studying a cell structure that is approximately 100 nm in size. Which of the following provides the lowest magnification you can use to see this structure?

E) scanning electron microscope

33) Which microscope uses two beams of light to produce a three-dimensional color image?

D) DIC microscope

34) Which microscope is used to see intracellular detail in a living cell?

B) two-photon microscope

35) Which microscope is used to observe viruses and the internal structure  of thinly sectioned cells?

A) transmission electron microscope

36) Which microscope is used to see detail of a 300-nm virus?

E) electron microscope

37) Assume you stain Bacillus by applying malachite green with heat and then counterstaining with safranin. Through the microscope, the green structures are

C) endospores.

38) Which step in the Gram stain is the critical step in differentiating gram-positive cells from gram-negative cells?

B) alcohol-acetone

39) You find colorless areas in cells in a gram-stained smear. What should you apply next?

D) an endospore stain

40) Which microscope is best used for observing the surfaces of intact cells and viruses?

E) scanning electron microscope

41) Bacterial smears are fixed before staining to

A) affix the cells to the slide.

42) The resolution of a microscope can be improved by changing the

C) wavelength of light.

43) A student is looking at a bacterial specimen using the oil immersion lens, but has forgotten to put immersion oil on the slide. The specimen will appear

C) somewhat fuzzy and have poor resolution.

44) The purpose of the ocular lens is to

B) magnify the image from the objective lens.

45) )  In microscopy, the term resolution

A) refers to the ability to distinguish fine structure and detail in a specimen.