NWHSU Microbiology Midterm Exam
Questions Correct Answers Current
Update (A+ Pass)
1. Which are cellular etiologic agents of infectious disease? - Answers -✔✔
"Eukaryotes (fungi, parasites) and prokaryotes (bacteria)"
2. Which are a-cellular etiologic agents of infectious disease? - Answers -✔✔ "Viruses,
virons, and prions"
3. Which groups of microorganisms are eukaryotic/prokaryotic? - Answers -✔✔ "a)
Eukaryotic: Protista -> Plantae, fungi, animalia b) Prokaryotic: Prokaryotae (monera)"
4. Name major differences between eukaryotic and prokaryotic cells. - Answers -✔✔
"a) Euk: Nucleus, nuclear envelope, more organelles, cytoskeleton (Plants and fungi
have cell walls) b) Prok: Nucleoid, cell wall, flagellum (Both have cytoplasmic
membrane, no cholesterol in prok.)"
5. What order of magnitude is the size of a bacterium? - Answers -✔✔ 10^-6 or micro
meters
"6. What is the structure and function of glycocalyces, flagella, fimbriae, pili?" - Answers
-✔✔ "Glycocalyx:Gelatinous sticky substance surrounding the outside of the cell,
composed of polysaccharides, polypeptides or both. 2 types exist: 1) A capsule acts as
camoflage (prevents bacteria from being recognized and slows down phagocytosis,
*virulence Factor. 2) Slime layer which is water soluble and allows prokaryotes to attach
to the surface, composes a biofilm. Flagella: motility, not present on all bacteria.
Fimbria: sticky bristle like projections, adherence to one another, host cells, and
environment. Shorter than flagella. Pili: hollow tubes used for DNA transfer
(Conjugation). Longer than fimbriae shorter than flagella. 1-2 per cell."
a. Which of these structures are known virulence factors? - Answers -✔✔
"Glycocalyces, flagella, fimbriae, pili"
b. Which of these structures contribute to biofilm formation? - Answers -✔✔
"Glycocalyx (slime layer), fimbrae"
c. Name the various types of flagella arrangements that can be used to identify bacteria.
- Answers -✔✔ "Monotrichous, amphitrichous, lophotrichous, peritrichous"
d. Which stain makes glycocalyces/capsules visible in the microscope? - Answers -✔✔
Gram stain?
, e. How do spirochetes move? - Answers -✔✔ Corkscrew motion
7. Name the major components of a gram-positive/gram-negative cell wall. What is the
appearance of gram-positive/gram-negative bacteria? - Answers -✔✔ "Gram positive
cell wall: Thick layer of peptidoglycan, containing unique polyalcohols called teichoic
acids. Gram stain appearance is purple. Gram negatice cell walls: Thin layer of
peptidoglycan, with an outer membrance containing proteins, and ippolysaccharides.
Produce endotoxins, and appear pink with the Gram stain. The endo toxin is a lipid A
molecule embeded in the outer membrane. "
8. What is the clinical importance of the difference between gram-positive and gram-
negative bacteria? - Answers -✔✔ "Gram positive bacteria are more resistant to
physical methods of control, which is important for clinical settings. Gram positive
bacteria are generally more suscetible to penicillin and bacteriostatic dyes. Gram
negative bacteria infections are more severe when the bacteria are killed or broken up
due to the production of endotoxins."
9. For which types of bacteria is the acid-fast stain used? Why is it needed? - Answers -
✔✔ "Organisms with a cell wall that is rich in lipids and waxes. The two general that
are acid fast include Mycobacterium and nocardia. The acid fast stain is used because
the walls are relatively impermeable, so heat is used to drive the stain into the cell wall.
The impermable wall also makes these organisms resilient to disinfectants. Extra care
must be taken when dealing with patients infected with acid fast genera."
11. How are cytoplasmic membranes of prokaryotes different from those of eukaryotes?
- Answers -✔✔ There's no cholesterol in the prokaryotic membrane
13. Compare aerobic cellular respiration and fermentation. - Answers -✔✔ See table
a. What gets recycled in fermentation for and for what purpose? - Answers -✔✔ NAD+
from NADH (NADH -> NAD+)
"b. What are some examples of non-medical applications of fermentation (industrial,
food,ƒ??)?" - Answers -✔✔ "CO2 and ethanol for wine and beer, acetone and is
propanol for nailpolish..."
"14. What are selective growth conditions (know MacConkeyƒ??s agar, as it is also
coming up in your lab final)" - Answers -✔✔ Media that allows the growth of certain
organisms while inhibiting others. Macconkeys agar is both selective and differential.
15. What are differential growth conditions? - Answers -✔✔ Media that differentiates
organisms with chemicals or certain dyes that cause organsims to product certain
characteristic changes or growth patterns.
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