WGU: D311 (ENDOTOXINS AND EXOTOXINS)
COMPREHENSIVE QUESTIONS AND CORRECT
ANSWERS EXAM PRACTICE\PREPARATION [GET ALL
RIGHT] GRADE A+
What does the presence of a clear area around a cell stained with India ink
indicate about the cell?
The cell has a capsule.
How do basic stains work?
The positively charged stain is attracted to the negatively charged portion of the cell.
Which staining technique is used to distinguish bacteria based on their ability to
produce structures that can survive extreme heat stress?
Endospore stain
Which aspect of a staining protocol enables dye to penetrate an endospore?
Heat
Why are the relationships between pathogenic microbes and their hosts
considered parasitic?
The microbe benefits from the interaction while the host is harmed.
Which characteristic of dracunculiasis has been pivotal to the success of its
eradication campaign?
Dracunculiasis has no animal reservoir.
Which type of organism would be most likely to grow on food stored in a
refrigerator or freezer?
A psychrophile would be most likely to grow on food stored in a refrigerator or freezer as
these microorganisms thrive in cold temperatures.
bacteriemia
presence of bacteria in the blood
pyemia
the presence of pus-forming organism in the blood
Viremia
viruses in the blood
toxemia
toxins in the blood
septicemia
growth of bacteria in the blood
septic
patients with septicemia
shock
a life-threatening decrease in blood pressure (systolic pressure <90 mm Hg) that
prevents cells and organs from receiving enough oxygen and nutrients
Exoenzymes
extracellular enzymes that pathogens produce to invade deeper into host tissues
, glycohydrolases example (Hyaluronidase S in Staphylococcus aureus)
degrades hyaluronic acid that cements cells together to promote spreading through
tissues
nucleases example (DNAse produced by S. aureus)
degrades DNA released by dying cells (bacteria and host cells) that can trap the
bacteria, thus promoting the spread
phospholipase (Phospholipase C of bacillus anthracis)
degrades phospholipid bilayer of host cells, causing cellular lysis, and degrade
membrane of phagosomes to enable escape into the cytoplasm
proteases (collagenase of clostridium perfringens)
degrade collagen in connective tissue to promote spread
toxins
biological poisons that assist in their ability to invade and cause damage to tissues
Toxigenicity
ability to produce a toxin
Endotoxin
A toxic component of the outer membrane of certain gram-negative bacteria that is
released only when the bacteria die.
Exotoxin
protein molecules that are produced by a wide variety of living pathogenic bacteria
the majority are produced by gram-positive pathogens
exotoxin
much more specific in their action and the cells they interact with
exotoxin
remains stable at high temperatures and requires heating at 121°C (250°F) for 45
minutes to inactivate
endotoxin
By contrast, most exotoxins are heat labile because of their protein structure, and
many are denatured (inactivated) at temperatures above 41°C (106°F).
exotoxin
protease
degrade protein and antibodies to protect bacterium from phagocytosis
coagulase
an exoenzyme that promotes blood-clotting. protects from immune system by hiding.
Kinase
digests blood clots.
Enterotoxin
a toxin produced in or affecting the intestines, such as those causing food poisoning or
cholera.
Neurotoxins
toxins that damage the nervous system
3 classes of exotoxins
intracellular targeting toxins, membrane disrupting toxins, and superantigens
intracellular targeting toxins
comprise two components: A for activity and B for binding
Membrane-disrupting toxins
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