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MCB 100 Exam 2 Questions and Answers Graded A+
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Exam of 6 pages for the course MCB at MCB (MCB 100 Exam 2)
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MCB 100 Exam 2What is the basis for assigning organisms into the three different domains of life
(Bacteria, Archaea, and Eukarya)? - answer rRNA gene sequences
a chain of bacilli - answer
Biofilm formation begins with - answer free-floating cells attaching to a surface
Which of the following statements about biofilms is TRUE?
A. In a single-species biofilm, the interior environment is uniform throughout.
B. The environment of the biofilm matrix is not conductive to uptake of colored dyes.
C. Biofilms cannot continue to grow at low nutrient concentrations
D. In biofilms there is often metabolic cooperation among bacteria.
E. In biofilms all the bacteria are living, but those that die are released into the medium.
- answer D. In biofilms there is often metabolic cooperation among bacteria.
Biofilms can be found benefiting our bodies ____________ - answer in the intestinal
tract
Why do doctors caution patents who are pregnant to avoid deli meats, cold cuts, and
soft cheeses? - answer The Listeria bacteria can grow in them when stored in the
refrigerator
Which of the following statements about Gram-positive Listeria is TRUE?
A. They produce powerful toxins that lyse and kill eukaryotic cells.
B. They form resistant endospores that can withstand harsh chemical environments.
C. They can invade and live within cells to avoid the host's immune system.
D. They move rapidly through the body using multiple flagella called comet tails.
E. They resist most antimicrobial agents due to biofilm formation. - answer C. They
can invade and live within cells to avoid the host's immune system.
Gram-negative bacteria can attach to surfaces via their _____________ - answer
fimbriae
A strain of the Gram-negative bacterium Vibrio cholerae, which causes the diarrheal
disease cholera, has a mutation that has caused the bacterium to lose the ability to
produce fimbriae and so it has become less virulent as a consequence. What function
has this pathogen lost? - answer The ability to adhere to a host cell
, Pathogenic strains of Gram-positive staphylococcus aureus can spread along tissue
planes to cause blistering by producing and secreting
____________________________ - answer a protease called exfoliative toxin
Gram-negative Haemophilus influenzae bacteria, which cause respiratory and ear
infections, require heme for their growth because _________________________ -
answer They need heme to bind to iron so they can transport iron inside them
Which of the following is a primary advantage for a bacterium having the ability to
invade and reside inside host cells?
A. The bacteria do not need their flagella to move from one location to another
B. The bacteria can colonize and form biofilms inside the cell.
C. Multiple bacteria can use the host cell as a compartment to exchange DNA with each
other.
D. The host cell can shield the bacteria from viruses and parasites.
E. The bacteria can hide and be protected from antibodies and immune cells. - answer
E. The bacteria can hide and be protected from antibodies and immune cells.
A strain of the Gram-negative bacterium Shigella flexneri, which causes the disease
dysentery (bloody diarrhea), has a mutation that has caused the bacterium to lose the
ability to produce a pore-forming toxin that makes pores in phagocytic membranes and
so it has become less virulent as a consequence. What function has this pathogen lost?
- answer The ability to escape the phagosome and enter the cytosol
Lipid A is _____________ that stimulates the body to release hormone-like chemicals
(called cytokines) that cause fever, inflammation, diarrhea, hemorrhaging, shock, and
blood coagulation. - answer an endotoxin found in bacterial membranes
Which of the following bacterial virulence factors directly contributes to severe
inflammation?
A. A hyaluronic acid-degrading enzyme like hyaluronidase
B. A blood-clot-degrading protease like staphylokinase
C. A extracellular matrix-degrading protease like collagenase
D. A superantigen like toxic shock syndrome toxin
E. A membrane pore-forming toxin like hemolysin - answer D. A superantigen like
toxic shock syndrome toxin
Diphtheria toxin is ___________________ that _________________ resulting in
__________________. - answer An Ab-type toxin | ADP-ribosylates EF2 | stopping
protein synthesis
A-B toxins are very modular and in nature can swap parts of their genes to make
chimeric toxins with new hybrid properties.
Suppose you have two A-B type toxins, A-B and A'-B'. A-B binds specifically to intestinal
cells and blocks protein synthesis to kill the cells. A'-B' binds specifically to neuronal
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