HW CHAPTER 3 Flashcards
(256 cards)
1
Q
Which of the following is more likely to cause urinary tract infections?
Fimbriated strains of Escherichia coli
Nonfimbriated strains of Escherichia coli
Both fimbriated and nonfimbriated strains of Escherichia coli
None of the answers are correct.
A
Fimbriated strains of Escherichia coli
2
Q
The major site of protein binding in DNA is the major groove. Why is this a good site for binding?
The major groove has lower frequencies of inverted repeats; this lower frequency of inverted repeats makes binding easier.
Because the minor groove is wider, it is more accessible to binding proteins.
Because the major groove is wider, it is more accessible to binding proteins.
The major groove has a more heavily methylated base composition, which aids in the binding of proteins.
A
Because the major groove is wider, it is more accessible to binding proteins.
3
Q
Regulation by induction and repression are called negative control because __________.
Transcription proceeds in the absence of the repressor protein.The organism wants transcription to occur only when the substrate (the activator protein) of the gene product is present.
Translation proceeds in the presence of the repressor protein.
Transcription proceeds in the presence of the repressor protein.
Translation proceeds in the absence of the repressor protein.
A
A
4
Q
Short regions at the beginning and end of gene sequences are not translated into proteins.
true/ false
A
true
5
Q
One way that regulation is often studied is by examining the effects of mutations. For example, mutations within the parts of the lac operon have been well studied. Which of these mutants would be considered a constitutive mutant?
a mutation that disables the promoter for the operon
a mutation in the gene for beta-galactosidase
a mutation in the gene for beta-galactosidase permease
a mutation that disables the repressor
A
a mutation that disables the repressor
6
Q
Which type of regulator(s) specifically binds to operator regions of DNA?
repressors and corepressors
repressors
activators and inducers
activators
A
repressors
7
Q
Some proteins that bind to DNA block transcription, whereas other proteins activate transcription
true/false
A
true
8
Q
Which of the following is an example of negative control using an inducible system?
The maltose operons in E. coli are turned off by defaul……
Glucose inhibits the synthesis of cyclic AMP and stimulates cyclic AMP ……
the trp operon in E. coli is turned on by default….
The lac operon in E. coli is turned off unless lactose is present……..
A
\
The lac operon in E. coli is turned off unless lactose is present……..
9
Q
The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur.
positive / inducer
negative / inducer
positive / activator
negative / activator
A
negative /inducer
10
Q
________ pathways typically rely on ________ proteins to inhibit mRNA synthesis.
Anabolic; repressor
Anabolic; activator
Catabolic; repressor
Catabolic; activator
A
A
11
Q
Which statement best explains why positively controlled genes have weak promoters and need an activator protein to help the RNA polymerase bind?
The organism wants transcription to occur only when the substrate (the activator protein) of the gene product is present.
The organism only wants translation to stop when the substrate (the activator protein) of the gene product is present.
The organism wants transcription to stop when the substrate (the activator protein) of the gene product is present.
The organism only wants translation to occur when the substrate (the activator protein) of the gene product is present.
A
A
12
Q
Enzyme repression typically affects catabolic pathways.
True
False
A
False
13
Q
The function of a kinase is
methylation.
glycosylation.
response regulation.
phosphorylation.
A
D
14
Q
Bacteria can regulate gene expression due to changes in the environment. How are these changes communicated to the cell?
A sensor kinase in the cytoplasm recognizes a change and transfers the information to a response regulator on the cell membrane.
A sensor kinase on the cell membrane recognizes the change and transfers the information to a response regulator in the cytoplasm.
A sensor kinase on the cell membrane recognizes the change and transfers the information to the repressor or inducer molecule, which then binds to DNA.
A response regulator on the cell membrane recognizes the change and transfers the information to a sensor kinase in the cytoplasm.
A
B
15
Q
Quorum sensing is a regulatory system that requires a certain cell density to work effectively. Each of the following activities utilizes quorum sensing EXCEPT
Staphylococcus aureus infection.
light emission by Aliivibrio fischeri.
transition of Candida albicans from budding yeast to elongated filaments.
flagella synthesis in Proteus vulgaris.
A
D
16
Q
A bacterium that either partially or fully catabolizes an acyl-homoserine lactone will likely disrupt
chemotaxis.
endospore formation.
quorum sensing.
attenuation.
A
C
17
Q
Quorum sensing relies upon a large cell population which then turns on transcription.
True
False
A
true
18
Q
Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________.
adenylate cyclase / transcriptional activation
cAMP receptor protein (CRP) synthase / catabolite repression
cAMP receptor protein (CRP) synthase / transcriptional activation
adenylate cyclase / catabolite repression
A
D
19
Q
Which of the following examples describes a type of catabolite repression?
View Available Hint(s)for Part A
Allolactose binds to a repressor, preventing it from binding to the operator of the lac operon.
The presence of abundant tryptophan inhibits the trp operon.
A mutation in the promoter of the lac operon prevents the expression of the genes needed for the bacterium to utilize lactose.
When glucose is present, the lac operon is inhibited.
A
D
20
Q
In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription?
The inducer binds to the operator.
The inducer causes the repressor to bind to the operator.
The inducer prevents the repressor from binding to the operator.
The inducer does not bind to the operator.
A
C
21
Q
A mutation in the gene encoding the lactose repressor (LacI) that prevents lactose from binding to the LacI protein would result in
constant repression of the lac operon in the presence of lactose.
constant expression of the lac operon in the presence of lactose.
constant expression of the lac operon in the absence of lactose.
constant repression of the lac operon in the absence of lactose.
A
A
22
Q
The preferential use of glucose over other available carbon substrates for growth is mechanistically explained by catabolite repression.
True
False
A
TRUE
23
Q
The synthesis of β
-galactosidase is regulated by __________.
View Available Hint(s)for Part A
induction
catabolite repression
repression
induction and catabolite repression
A
D
24
Q
Cyclic AMP (cAMP) is involved in the global regulation of catabolic pathways in Escherichia coli, including the lac operon. A high activity of the enzyme adenylate cyclase, which makes cAMP, is suggestive of catabolite repression.
True
False
A
FALSE
25
All of the following are functions of heat shock proteins in bacteria EXCEPT
degradation of denatured proteins.
responding to exposure to high levels of ethanol.
stimulation of binary fission.
prevention of inappropriate protein subunit aggregation.
C
26
The most frequent way in which small regulatory RNA molecules exert their effects is by
binding to a repressor and repressing enzyme transcription.
base pairing with other RNA molecules that have regions of complementary sequence.
signal transduction.
acting as an inducer that then binds to an activator protein to allow transcription to proceed.
B
27
How would you design an sRNA to bind to a sequence?
take the complementary sequence of 200 continuous nucleotides
select 200 continuous nucleotides from the sequence
select six continuous nucleotides from the sequence
take the complementary sequence of six continuous nucleotides
A
28
Attenuation is a type of regulation that can control
translational activity exclusively.
allosteric enzyme activity.
transcriptional activity exclusively.
both transcriptional and translational activity.
C
29
Which regulatory mechanism does NOT depend on a conformational change in protein/enzyme structure to change activity?
feedback inhibition
attenuation
negative control
catabolite repression
B
30
Which of the following is a characteristic of an isoenzyme?
The same reaction can be catalyzed by multiple enzyme variants.
More than one gene makes the same enzyme.
Multiple binding sites on the same enzyme enable multiple regulation mechanisms.
More than one enzyme is regulated by the same mechanism.
A
31
Regulation of enzyme activity occurs
at the start of transcription.
posttranslationally.
at the start of translation.
at any point on the enzymatic production pathway
B
32
mutant that has a nutritional requirement for growth is an example of a(n)
heterotroph.
auxotroph.
autotroph.
organotroph.
Auxotrophs
33
Selective pressure must be maintained on a cell for that cell to retain its plasmid.
True
False
True
34
Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?
silent mutation
missense mutation
frameshift mutation
nonsense mutation
silent
35
Microinsertions and microdeletions often result in ________ mutations.
auxotrophic
silent
advantageous
frameshift
frameshift
36
Consider the following experiment. First, large populations of two mutant strains of Escherichia coli are mixed, each requiring a different, single amino acid. After plating them onto a minimal medium, 45 colonies grew. Which of the following may explain this result?
The colonies may be due to back mutation (reversion).
The colonies may be due to recombination.
The colonies may be formed either due to back mutation (reversion) or recombination.
The colonies may be formed neither due to back mutation (reversion) nor recombination.
C
37
If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium without ampicillin, it may
gain resistance to other antibiotics.
undergo a reversion mutation.
transfer resistance to other cultures in the laboratory.
lose the plasmid because there is no selection for ampicillin resistance.
D
38
The killing of cells by UV irradiation involves
formation of purine dimers.
formation of pyrimidine dimers.
absorption at 260 nm by proteins only.
absorption at 260 nm by RNA only.
B
39
When damaged or single-stranded DNA activates the RecA protein, the RecA protein stimulates the cleavage of LexA. This results in
derepression of the SOS system.
repression of polymerase V and activation of endonuclease.
increased transduction and recombination.
activation of the Hfr system.
A
39
Horizontal gene transfer
is common and may sometime occur between unrelated organisms.
does not provide an advantage to organisms.
is rare and only occurs between closely related strains.
only occurs in prokaryotes.
A
40
The production of a functional gene product by transforming bacteria that lack a lacZ gene with a plasmid containing a lacZ gene is known as
complementation.
mitosis.
reversion.
transfection.
Complementation
40
Which of the following is NOT required for homologous recombination?
an Hfr chromosome
RecA
proteins having helicase activity
endonuclease
A
41
The uptake of free DNA from the environment is referred to as ________, while the transfer of DNA with cell-to-cell contact is known as ________.
transformation / transduction
transduction / conjugation
transformation / conjugation
conjugation / transformation
C
42
Toxigenicity in Corynebacterium diphtheriae is due to phage conversion.
True
False
TRUE
43
Which process listed below allows genetic material to be transferred from a virus-like particle that lacks genes for its own replication?
gene transfer through a gene transfer agent
conjugation of an F+ plasmid
transduction by a dsDNA phage Mu
transformation of a linear piece of DNA
A
44
F+ strains of Escherichia coli
do not have an F factor.
have an integrated F factor.
have the F factor as a plasmid.
transfer the F factor to recipient cells at a high frequency.
C
45
The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA.
transformation
transduction
pili
SOS repair
C
46
All Hfr strains integrate into the chromosome at
the same locus.
several specific sites.
the same locus most of the time, although there may be some variation.
loci that cannot be accurately determined.
B
47
Transposons can be found on many genetic elements, including plasmids, chromosomes, and viral genomes.
True
False
T
48
The CRISPR system
recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.
synthesizes gene transfer agents during stationary phase.
repairs DNA and increases DNA damage tolerance during times of stress.
facilitates homologous recombination through a complex system of proteins and clustered repeats.
A
49
Insertion sequences are found on both ends of transposons and encode for transposase.
True
False
TRUE
50
Compared with pure cultures grown in the lab, microbes in nature usually experience a wider range of environmental conditions, more variation in conditions over time, and more contact with other organisms. Therefore, the same organism in nature will __________.
carry out completely different metabolisms than in pure culture
typically grow faster than in pure culture
typically grow only on surfaces
typically grow slower than in pure culture
D
51
According to ecological theory, each organism has one place where it will be most successful, called the __________.
fundamental niche
guild
realized niche
microenvironment
C
52
Microbial diversity in an ecosystem can be expressed as the number of different species present, which is termed __________.
microbial community
species abundance
microbial population
species richness
D
53
All of the following are true of biofilms EXCEPT that __________.
View Available Hint(s)for Part A
biofilms form on virtually all submerged surfaces in nature
biofilm formation and dispersal are regulated processes
biofilms are composed of only one species at a time
biofilms protect organisms from antibiotics
C
54
One characteristic of a biofilm is __________.
View Available Hint(s)for Part A
the presence of a cellulose matrix to hold the organisms together
the presence of one or more species of bacteria
bacteria do not have to be attached to a surface
a single layer of cells
B
55
Bacteria will benefit as part of a biofilm because __________.
it allows all compounds in the environment to diffuse to the organism's location much faster
it allows them to remain in a favorable niche
it allows them to live separated from other bacteria
it allows them to be phagocytosed easier
B
56
Organisms that grow best under elevated pressure like you would find in the deep ocean are __________.
piezophiles
compressionphiles
tensionphiles
barometric
A
57
he rhizosphere is __________.
the surface of the roots of a plant
the top inch of soil that contains a large number of microorganisms
the soil immediately surrounding the root of a plant
all of the microorganisms living in soil
C
58
A small farm pond containing many species of microorganisms (bacteria, cyanobacteria, algae, and protozoa) was perturbed when runoff from a manure pile entered the pond. The added nutrients soon turned the water green due to a bloom of cyanobacteria. How did this affect the microbial community in the pond?
View Available Hint(s)for Part A
Species richness increased and species abundance increased.
Species richness increased and species abundance decreased.
Species richness decreased and species abundance increased
.
Species richness decreased and species abundance decreased.
C
59
In a body of freshwater, the transition between the warmer upper layers and the colder lower layers of water is called the __________.
planktonic
thermocline
hypolimnion
epilimnion
B
60
If the biochemical oxygen demand (BOD) of a lake is very high, how will that affect the aquatic life in the lake?
There will be less oxygen available for the aquatic life due to the microbial activity.
There will be more oxygen available for the aquatic life but much less oxygen available to the microbial populations.
The BOD does not have an impact on available oxygen in the lake.
There will be more oxygen available for the aquatic life due to the microbial activity.
A
61
Given the extremely low concentrations of nutrients in the open ocean, most marine Bacteria typically need all of the following adaptations EXCEPT __________.
proteorhodopsins
many periplasmic binding proteins
high surface area-to-volume ratios
large cell size
D
62
While most of the oil spilled into the Gulf of Mexico from the Deepwater Horizon drilling rig in 2010 has disappeared, some of the oil spilled from the Exxon Valdez oil tanker into Prince William Sound, Alaska, in 1989 still remains in the coastal sand and sediments. What possible differences in these two spills could account for the different rates of petroleum degradation?
the amount of oil spilled and the seawater salts composition
seawater salt composition and types of bacteria
ambient temperatures and the types of hydrocarbons present
the types of bacteria present and the amount of oxygen in the water
C
63
Based on your knowledge of hydrocarbon degradation, what is one factor that most likely limited the rate of petroleum degradation after the Exxon Valdez oil spill off the coast of Alaska?
Salt concentration
Inorganic nutrient concentrations
Chemical dispersants
O2 concentration
B
64
Compounds that are NOT produced by organisms anywhere in nature are called __________.
View Available Hint(s)for Part A
foreign
xenobiotic
xerobiotic
abiotic
B
65
The type of wastewater treatment that would be used to reduce the BOD (biological oxygen demand) of liquid waste would be __________.
View Available Hint(s)for Part A
advanced tertiary treatment
primary treatment
aerobic activated
sludge
anaerobic digestion
C
66
Microbes are sometimes used in secondary treatment of wastewater to
convert heavy metals into carbon dioxide.
remove large particles.
remove organic matter.
convert heavy metals
into carbon dioxide,
remove organic matter, and remove large particles.
C
67
With increased levels of oxidizable materials, the biochemical oxygen demand (BOD) will
remain the same.
increase.
decrease.
increase or decrease depending on the nature of the materials involved.
INCREASE
68
Which treatment method(s) are used in primary wastewater treatment?
Chemical only
Biological only
Physical separation only
Biological, chemical, and physical separation
C
69
Aerobic secondary treatment is usually best for ________ wastewater.
chemical
residential
industrial
agricultural
B
70
During secondary aerobic wastewater treatment, some of the activated sludge goes ________ while the rest goes ________.
back to the primary system / to the tertiary digester
back to the primary system / to the aerator
to the anoxic digester / back to the primary system
back to the aerator / to the anoxic sludge digester
D
71
Effluent water is wastewater
that has undergone anoxic secondary wastewater treatment.
discharged from the wastewater treatment facility.
discharged from the pharmaceutical, plastics, and petrochemical industries.
that is imported to the wastewater treatment facility for treatment.
B
72
Microbes are involved in which step(s) of wastewater treatment?
primary and secondary
secondary and tertiary
secondary only
primary only
B
73
The goal of wastewater treatment is to
remove pathogens from wastewater before it is released.
produce potable water.
reduce organic and inorganic materials in wastewater to a level that no longer supports microbial growth.
remove pathogens from wastewater to produce potable water.
C
74
The goal of tertiary wastewater treatment is to sharply reduce the levels of ________ from the final effluent.
organic compounds
heavy metals
methane
inorganic nutrients
D
75
Physical separation of solids and organic and inorganic particulates from sewage is termed __________.
sand filtration
tertiary wastewater treatment
secondary wastewater treatment
primary wastewater treatment
D
76
dvanced wastewater treatment includes __________.
View Available Hint(s)for Part A
removing additional suspended solids
adding organic matter
adding inorganic
nutrients for microbial growth
removing only organic matter
A
77
Why are bioactive pollutants like prescription medications a challenge for wastewater treatment?
Degradation produces chemicals that are more harmful to the environment.
They are only occasionally found in treated sewage
.
They may not support microbial growth.
They are present at high concentrations toxic to microorganisms.
C
78
Which product of anoxic sewage treatment can be used to heat and power an entire water treatment facility?
O2
CO2
H2
CH4
D
79
An engineer working for the Peace Corps is helping a small town in Africa design a drinking water purification system. The raw water supply from the nearby river has high levels of suspended solids, dissolved organic carbon, and bacterial load. What would be the most effective order for the water treatment processes?
View Available Hint(s)for Part A
sedimentation, coagulation, filtration, disinfection
filtration, coagulation, sedimentation, disinfection
disinfection, sedimentation, coagulation, filtration
sedimentation, disinfection, coagulation, filtration
A
80
To further reduce the possibility of biological contamination, most treatment plants treat the effluent with
fluorine.
extreme heat.
chlorine.
ozone.
C
81
The use of ________ to treat drinking water, which began in 1913, reduces the incidence of waterborne diseases.
coagulation
chlorination
UV irradiation
filtration
B
82
There is a large plastic container of water by the soccer fields. It is labeled not potable. Should the soccer players drink this water?
It depends on the color of the water.
It depends on the turbidity of the water.
No; it is not safe to drink.
It is safe to drink if it doesn't smell funny.
C
83
Which choice provides the steps in drinking water treatment in the correct order?
View Available Hint(s)for Part A
filtration, sedimentation, coagulation, disinfection, storage
sedimentation, coagulation, filtration, disinfection, storage
filtration, disinfection, coagulation, sedimentation, storage
coagulation, sedimentation, filtration, disinfection, storage
B
84
BOTH physical and chemical methods are used to treat and purify drinking water.
True
False
T
85
Potable water is NOT safe for human consumption.
True
False
F
86
In water, most taste- and odor-producing compounds are inorganic in nature.
True
False
F
87
Which of the following bacterial pathogens is found in water distribution systems?
Vibrio cholerae
Legionella pneumophila
Enterobacter aerogenes
Klebsiella pneumoniae
B
88
Water distribution systems contain
biofilms that may harbor opportunistic pathogens.
no microbial growth substrates.
sediment and flocs.
very few bacteria or other microorganisms.
A
89
Opportunistic pathogens such as Legionella, Pseudomonas, and Mycobacterium species have the ability to grow within ________, which may enhance their ability to survive in water distribution systems.
UV irradiated water
fish
human saliva
protists
PROTISTS
90
Which of the following can be completely degraded to carbon dioxide by microorganisms?
Inorganic pollutants
Xenobiotics
Uranium
Petroleum
D
91
Which of the following hydrocarbon compounds are most recalcitrant to degradation during bioremediation, meaning that they stay in the environment longer than the others?
straight-chain hydrocarbons
natural gases such as ethane and propane
polycyclic hydrocarbons
methane
C
92
Organisms that degrade hydrocarbons in crude oil are ubiquitous in the environment and have evolved special strategies, such as surfactant production, that allow them to readily use hydrocarbons as electron donors and carbon sources.
True
False
T
93
Why are some xenobiotics biodegraded slower than crude oil and petroleum products?
Xenobiotics were designed to inhibit microbial growth.
Only cometabolic microbial processes degrade xenobiotics
.
Microorganisms have not yet evolved to effectively degrade novel xenobiotic compounds.
Chlorinated compounds are so toxic that biodegradation is not possible.
C
94
Microbial plastics are composed of
polyhydroxyalkanoates (PHAs).
xenobiotics.
polysaccharides.
polyaromatic hydrocarbons.
A
95
Reductive dechlorination is important in the breakdown of chlorinated xenobiotics because
reductive dechlorination breaks down all halogen compounds.
these compounds do not leach into groundwater or sediment.
anoxic conditions develop rapidly in polluted habitats.
aerobic breakdown of xenobiotics is not possible under any circumstances.
C
96
Reductive dechlorination is a process in which
halogenase enzymes remove chlorine from chlorinated compounds.
carbon dioxide is the primary end product.
only dichloro compounds can be degraded.
oxygenase enzymes add oxygen to chlorinated compounds.
A
97
Synthetic plastics are
more expensive than microbial plastics.
constructed from PHAs.
oxidized completely to carbon dioxide after a few years under aerobic conditions.
slower to degrade than microbial plastics.
D
98
Chlorinated xenobiotics can ONLY be degraded aerobically, thus making them very recalcitrant if they accumulate in anoxic environments.
True
False
F
99
Most wastewater treatment facilities employ methods designed to detect each pathogenic organism that may be present in a given sample.
True
False
F
100
Water leaving an efficient wastewater treatment facility ideally has a biochemical oxygen demand (BOD) between ________ units.
5 and 25
25 and 50
50 and 100
0 and 5
D
101
How do treatment systems select for granular sludge formation?
By using phosphorus-accumulating organisms to generate PHA
By a series of grates and screens
By spraying wastewater over bed of rocks
By removing suspended floc material that does not settle rapidly
D
102
What is the advantage of enhanced biological phosphorus removal (EBPR) over chemical precipitation?
EBPR removes significantly more phosphorus than chemical precipitation.
Chemical precipitation produces sludge containing arsenic.
EBPR is a more stable process.
Significantly, less sludge is produced by EBPR compared to chemical precipitation.
D
103
The cost of reactive nitrogen removal can be decreased by promoting nitrite oxidation.
True
False
F
104
Tertiary wastewater treatment may use both aerobic and anaerobic processes.
True
False
T
105
What is necessary in a side stream brine in order to use the anammox process for nitrogen removal?
Enhanced biological phosphorus removal
Chlorination
Partial nitration
Trickling filter
C
106
Which process produces a gaseous product that can be used as fuel to provide heat or power for a wastewater treatment plant?
Primary wastewater treatment
Anaerobic sludge treatment
Aerobic sludge treatment
Trickling filter secondary wastewater treatment
B
107
Treatment of drinking water by UV irradiation is effective at ________, but is less effective at ________.
killing viruses / killing bacteria and eukaryotic pathogens
killing bacteria and viruses / killing eukaryotic pathogens
killing bacteria and some cysts / killing viruses
removing odor- and taste-altering organic compounds / killing bacteria
C
108
Secondary disinfection of drinking water is necessary to
completely prevent the formation of biofilms on pipes in the water distribution system.
maintain sufficient residual in the water distribution system to inhibit microbial growth.
kill Cryptosporidium and other resistant pathogens.
neutralize taste- and odor-producing organic compounds.
B
109
Chlorine is consumed when it reacts with organic materials.
True
False
T
110
Water disinfection agents such as chlorine can easily kill Cryptosporidium.
True
False
F
111
It is possible to completely eliminate microorganisms from water distribution systems if sufficient amounts of chlorine are used.
True
False
F
112
Subway air and water distribution systems harbor dangerous levels of pathogenic microorganisms.
True
False
F
113
How does the diversity of bacteria and fungi differ between outdoor and indoor environments?
There is a greater diversity indoors than outdoors.
It depends on the local geography.
There is a greater diversity outdoors than indoors.
While the species differ, the diversity is similar.
A
114
An increase in childhood allergies and autoimmune disorders in developed countries has been linked to reduced exposure to microbes in the indoor environment.
True
False
T
115
The best choice for estimating the viable cell number of a water sample would be the __________.
View Available Hint(s)for Part A
spectrophotometric method
agar dilution tube method
most probable number technique
streak plating method
C
116
Fluorescent in situ hybridization (FISH) can be used to determine __________.
View Available Hint(s)for Part A
how many Salmonella typhimurium cells are present in a sample of unpasteurized apple juice
whether a specific piece of mRNA is being produced
the phylogenetic diversity of an environmental sample
all of the listed conditions
D
117
The phylogenetic diversity analysis of complex microbial communities often targets small subunit (SSU) ribosomal RNA genes. This is because rRNA is found in all organisms and __________.
View Available Hint(s)for Part A
is made by cells only at certain times
is highly conserved over evolutionary time
has more genes than mRNA
is easier to extract from samples
B
118
Genes that retain their function yet change over evolutionary time as organisms diverge are called orthologs. Organisms with identical or very similar orthologous genes belong to the same __________.
phenotype
genotype
phylotype
ribotype
C
119
Phylogenetic analysis of microbial communities in nature using various PCR techniques has revealed that only a minority of phylotypes have been cultured from the environment and the most common phylotypes have not been grown in in the laboratory. This is due in part to __________.
View Available Hint(s)for Part A
lack of sufficient sampling of the community
poor technique
the uncultured organisms' being rare in the community
enrichment bias
D
120
Select the option that lists the steps necessary for PCR analysis of a microbial community in the correct order.
View Available Hint(s)for Part A
microbial sample collection; PCR of target genes; DNA extraction; sorting by electrophoresis; analysis
PCR of target genes; microbial sample collection; DNA extraction; sorting by electrophoresis; analysis
microbial sample collection; sorting by electrophoresis; analysis; DNA extraction; PCR of target genes
microbial sample collection; DNA extraction; PCR of target genes; sorting by electrophoresis; analysis
D
121
Microarrays that have been designed to screen samples for specific groups of bacteria are called __________.
View Available Hint(s)for Part A
biochips
phylochips
microchips
phytochips
B
122
Metagenomics involves the analysis of a microbial community by __________.
generating a phylogenetic tree based on all of the versions of a gene in an environment
sampling and sequencing all of the genes in an environment
generating a complete sequence of the genomes of all of the organisms in an environment
sequencing all of the community RNA in an environment
B
123
Metagenomics is a more sensitive analysis of community diversity than rRNA-based analyses because __________.
View Available Hint(s)for Part A
the extraction of the DNA from the environmental samples is more efficient
rRNA genes are not found in all of the organisms present in the environment
genes do not have to be amplified by PCR before being sequenced
more clone libraries can be assembled
C
124
By isolating total community RNA, using reverse transcriptase to make cDNA copies of it, and then sequencing the cDNA, ecologists can __________.
View Available Hint(s)for Part A
determine the community genomic potential at the moment of sampling
determine the community genome expression at the moment of sampling
determine the community metabolic activity at the moment of sampling
determine the community genome translation at the moment of sampling
B
125
Which definition is NOT correctly matched to the genomic field of study?
View Available Hint(s)for Part A
metagenomics: study of the DNA sequences found in a microbial community
metaproteomics: study of the diversity and abundance of proteins in a microbial community
metaproteomics: study of the abundance of proteins in a microbial community
metatranscriptomics: study of the RNA sequences found in a microbial community
C
126
What is the process that will amplify DNA from a single cell isolated from a natural microbial community?
View Available Hint(s)for Part A
polymerase chain reaction
multiple displacement amplification
polymerase chain amplification
You cannot amplify the DNA from a single cell isolated from an environmental sample.
B
127
When a DNA gel is run, a standard sample with fragments of known size is often run in one well. Why is it important to use a standard sample?
View Available Hint(s)for Part A
The standard sample helps to make the other samples more visible.
When an electrophoresis gel is run, small differences in the environment (e.g., the gel composition and current) can influence how far the fragments travel. Having a standard sample allows one to compare the test fragments with fragments of known size that have been run under the same conditions.
The standard sample is used to make sure that the electrical current is working properly.
The standard sample is used to demonstrate that the apparatus is working properly; it is a control.
B (long ash)
128
What might be a reason that a researcher would decide to use Northern blotting instead of Southern blotting?
View Available Hint(s)for Part A
to determine whether gene amplification was used to increase transcription of a gene in a particular organism
to determine the extent to which a gene is being transcribed in a particular tissue
to determine the extent to which a gene is being translated in a particular tissue
to compare the proteins present in different cells
B
129
Which of the following is true about hybridization?
View Available Hint(s)for Part A
DNA strands that differ in a few bases may still be able to hybridize
When used as probes, DNA can hybridize only with DNA, and RNA can hybridize only with RNA.
DNA strands must be completely complementary in order to hybridize, although RNA strands can hybridize with DNA or RNA even if there are some differences in the base sequences.
RNA strands must be entirely complementary in order to hybridize, although DNA strands can hybridize with DNA or RNA even if there are some differences in the base sequences.
A
130
What is the most important advantage of Pfu polymerase over Taq polymerase?
It is from a bacterium, not an archaean, so it is more effective for replicating eukaryotic DNA.
Unlike Taq polymerase, Pfu polymerase functions well at relatively high temperatures.
Pfu polymerase removes the need for primers during PCR.
Unlike Taq polymerase, Pfu polymerase has proofreading activity.
D
131
Which time period(s) during PCR thermocycling is/are hottest in temperature?
During primer annealing
During DNA denaturation
During primer extension/elongation
Both the first and last cycles are hotter in temperature than all other cycles.
B
132
Electrophoresis can be used to separate molecules by size, shape, and charge. When DNA samples are run in an electrophoresis gel, the different bands produced generally represent fragments of different sizes. Why is the size of the fragment the most critical factor in determining how far it migrates on a gel when DNA fragments are compared?
View Available Hint(s)for Part A
The shape of the DNA fragments has an even greater effect on movement than size or charge, so charge is relatively unimportant.
The charge on DNA is so small that it has a minimal effect on movement in the gel.
A special type of gel is used for DNA electrophoresis to minimize the effects of charge.
DNA moves toward a positive charge due to the negative charge on its phosphate groups. The charge is consistent because all DNA nucleotides have a single phosphate group rather than having more diverse patterns of charges. Because the charge is relatively consistent, size is the most important factor determining how far fragments move.
D
133
Restriction endonucleases are found in nature. They are extremely useful for genetic engineering. Why do organisms produce them?
View Available Hint(s)for Part A
Because they cut only at specific sequences in DNA, they are useful in cutting harmful DNA (such as viral DNA) without harming the organism that produces them (which can protect those sequences in its own DNA).
They are involved in DNA replication in prokaryotes.
They are part of the viral life cycle and help in the assembly of new viruses.
Organisms produce them as a way of allowing new genetic material to be inserted.
A
134
Which of the following sequences is a palindrome, characteristic of many recognition sequences for restriction endonucleases?
GGGGGGG
CCCCCCCC
TTGCCGA
AACGGCT
GTAATG
CATTAC
GAATTC
CTTAAG
D
135
Which of the following is NOT a common step in molecular cloning using plasmids?
Ligate DNA into vectors.
Fragment DNA into small segments.
Insert the vectors into a host.
Hybridize DNA sequences with slightly mismatched oligonucleotides.
D
136
Cloning vectors can be distinguished from expression vectors by
having a multiple cloning site (MCS).
lacking a promoter site upstream of the insertion site.
carrying ori genes for replication of the cloned sequence.
having a high copy number per cell.
B
137
Which choice below lists the steps necessary for genetic cloning in the correct order?
View Available Hint(s)for Part A
isolate DNA of interest; fragment the DNA; insert DNA into vector; insert vector into host; host replication of recombinant vector
isolate DNA of interest; fragment the DNA; insert vector into host; insert DNA into vector; host replication of recombinant vector
isolate DNA of interest; fragment the DNA; host replication of recombinant vector; insert DNA into vector; insert vector into host
fragment the DNA; insert DNA into vector; insert vector into host; host replication of recombinant vector; isolate DNA of interest
A
138
Cells that have "insertional inactivation" of the lacZ gene are
white.
yellow.
blue.
fluorescent green.
white
139
Expression vectors are designed to ensure that ________ can be efficiently ________.
mRNA / translated
DNA / transcribed
mRNA / transcribed
DNA / translated
C
140
Strong promoters used for genetic manipulation are usually regulated by specific molecules.
True
False
T
141
One method to circumvent issues with introns when expressing a eukaryotic gene in a bacterium is to simply clone the mature transcript.
True
False
T
142
What makes eukaryotic transcripts easier to isolate than bacterial transcripts?
Transcripts are the most abundant RNAs in eukaryotes.
mRNA is polyadenylated in eukaryotes.
Eukaryotic transcripts are not methylated but their genes are often methylated.
Larger transcript size in eukaryotes enables easy size-selection methods.
B
143
High expression levels of a eukaryotic gene in a bacterium such as Escherichia coli cannot be accomplished due to the presence of introns.
True
False
F
144
A common reporter protein is green fluorescent protein (GFP).
True
False
T
145
The lacZ gene is commonly used as a reporter gene because its substrate, lactose, is well known and easily measured.
True
False
F
146
Green fluorescent protein (GFP) is used for detecting translational activity of a fused protein, whereas lacZ reporters are used to detect transcriptional activity of a fused gene.
True
False
F
147
Reporter genes can be used to __________.
View Available Hint(s)for Part A
detect the presence of a genetic element
detect if DNA was inserted in a vector
detect the absence of a genetic element.
All of the listed responses are correct.
D
148
The Ti plasmid is best suited for genetically manipulating
fish.
viruses.
Agrobacterium spp.
plants.
plants
149
The principle underlying how salmon were genetically engineered to grow faster is the
resistance to bacterial infections which waste metabolic energy in the salmon to fight off.
removal of a gene responsible for feeling full after eating.
addition of genes to enhance blood circulation and tissue development.
replacement of inducible to constitutive hormone production.
D
150
Recognizing pathogens that contain multiple unique proteins which enable the human immune system to recognize just one and mount an effective response has opened the door on development of some vaccines only being
subunit vaccines.
attenuated carrier viruses.
monovalent.
purified protein administered.
A
151
Genetically engineered vaccines can be created by __________.
View Available Hint(s)for Part A
removing virulence genes from a pathogen
purifying a specific subunit of a pathogen
adding virulence genes from a pathogen to a non-virulent organism
All of the listed responses are correct.
D
152
The term "phage" is generally reserved for the viruses that infect
plants.
animals.
bacteria.
multiple species.
bacteria
153
When a virus enters a host cell in which it can replicate, the process is called a(n)
prophage.
excision.
infection.
insertion.
C
154
Enveloped viral membranes are generally ________ with associated virus-specific ________.
protein bilayers / lipids
lipid bilayers / proteins
glycolipid bilayers / phospholipids
lipid bilayers / phospholipids
B
155
egarding the viral membrane of an enveloped virus, the lipids are derived from the ________, and the proteins are encoded by ________.
host's cell membrane / host's genes
virion / host's genes
virion / viral genes
host's cell membrane / viral genes
D
156
All viral particles
are smaller than bacterial cells.
contain an envelope to prevent its degradation outside of a host.
are metabolically inert.
exhibit cell lysis under a particular condition.
C
157
Viral size is generally measured in
centimeters.
nanometers.
picometers.
micrometers.
b
158
which statement is TRUE?
The origins of the nucleic acid polymerases used by viruses are eukaryotic.
All viruses contain their own nucleic acid polymerases.
RNA viruses contain their own nucleic acid polymerases.
Viruses do not contain their own nucleic acid polymerases.
C
159
Reverse transcriptase is a(n)
RNA-dependent RNA polymerase.
RNA-dependent DNA polymerase.
DNA-dependent RNA polymerase.
DNA-dependent DNA polymerase.
B
160
Which of the following enzymes would you expect to find in the virion of a retrovirus, but NOT in a bacteriophage?
lysozyme
methylase
restriction enzymes
reverse transcriptase
D
161
When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus
concatemer.
envelope.
nucleocapsid.
capsid.
C
162
Which of the following are the hosts for most enveloped viruses?
animals
fungi
Archaea
Bacteria
A
163
Virus assembly requires host cell mediated reactions.
True
False
f
164
The size and shape of viral particles is largely governed by the size and packaging of the viral
enzymes.
envelope.
genome.
prophage.
C
165
Rod-shaped viruses have icosahedral symmetry while spherical viruses have helical symmetry.
True
False
F
166
The growth of viruses in a culture is described as a one-step growth curve, because
the eclipse phase prevents the plating and enumeration of virions although new virions are produced at a steady rate during the eclipse phase.
there is only one step in the viral life cycle which leads to only one replicative cycle in a culture.
virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.
assembly and release actually occur in one step.
C
167
When a solution composed of bacteria and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.
insertion sequences
plaques
prophages
colonies
B
168
Viruses infecting ________ are typically the easiest to grow in the laboratory.
prokaryotes
animals
plants
fungi
A
169
Viral replication is
dependent on the host cell's DNA, RNA, enzymes, and metabolism.
independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.
dependent on the host cell's DNA and RNA.
independent of both the host cell's DNA and the host cell's enzymes and metabolism.
B
170
Viral replication occurs
extracellularly.
intracellularly.
both intracellularly and extracellularly.
either intracellularly or extracellularly, depending on the virus involved.
B
171
A cell that allows the complete replication cycle of a virus to take place is said to be a
permissive host.
lytic cell.
viral cell.
dead cell.
A
172
For bacteriophages and animal viruses ________ is the step in the viral life cycle that determines host cell specificity.
assembly
synthesis
attachment
penetration
C
173
Penetration requires that the entire virus is inserted within the host.
True
False
F
174
The latent phase in the viral growth curve and the lag phase of the bacterial growth curve are equivalent and represent the time it takes for the virus or bacterium to adapt to the culture conditions and begin growing.
True
False
F
175
Retroviruses are medically important viruses because
they include the poliovirus.
they include some viruses that cause cancer and HIV.
they include all human pathogenic viruses.
they include the influenza virus.
B
176
The majority of many important human viral diseases are caused by
ssDNA viruses.
dsRNA viruses.
ssRNA viruses.
dsDNA viruses.
C
177
What are the possible consequences of viral infection of an animal cell?
lysis or lysogeny
lysogeny followed by eventual lysis
rapid lysis or latent infections
Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer.
D
178
For a virus to cause a latent infection, it must possess
dsRNA.
ds DNA.
ssDNA.
Any type of viral genome can lead to a latent infection.
dsDNA
179
Budding of virions from an infected host results in enveloped virus.
True
False
T
180
The genome of a retrovirus consists of dsRNA.
True
False
F
181
Lysogeny is unique to bacteriophages; similar relationships have not been found among the animal viruses.
True
False
F
182
Influenza virus targets
throat epithelium.
respiratory epithelium.
gastrointestinal cells.
oral cavity cells.
B
183
An outer coat consisting of a dense, well-defined polymer layer surrounding a cell and used in attachment is called a
capsule.
pilus.
lipopolysaccharide layer.
cytoplasmic membrane.
A
184
Which of the following is NOT important for the adherence of bacteria to host tissues?
lipopolysaccharides
capsule
adhesins
slime layer
A
185
The collective term for the organisms living on or in the human body, as opposed to a general term for organisms in an environmental habitat, is
pathogens.
transient microbial flora.
the human microbiome.'
the microbiota.
C
186
Which of the following is TRUE about flagella?
They are not involved in adherence and colonization at all.
They may be involved in adherence to a lesser extent than pili and fimbriae.
They are as important in adherence as pili and fimbriae.
They are the most important structure in adherence.
B
187
________ is a damage or injury to a host organism that impairs its function.
Trauma
Disease
Transmission
Infection
B
188
Which of the following pathogens does NOT use capsules or a slime layer for attachment?
Bacillus anthracis
Vibrio cholera
Streptococcus pneumonia
All of these pathogens use capsules or slime layers for attachment.
B
189
he best term to describe the general process by which microorganisms cause diseases is known as
pathogenesis.
infection.
invasion.
virulence.
A
190
The process by which white blood cells ingest and kill bacteria is called
phagocytosis.
transcription.
exocytosis.
translation.
A
190
The macromolecules responsible for bacterial adherence that are NOT covalently attached to bacteria are collectively called
glycocalyx.
lipid A.
capsules.
biofilms.
A
191
What is the difference between adherence and colonization?
Colonization occurs when microbes begin to spread in host tissues, whereas adherence occurs when microbes first begin to reproduce in the host tissues.
Colonization occurs when microbes begin to spread in host tissues, whereas adherence occurs when microbes initially attach.
Colonization occurs when a microbe begins to grow in host tissues, whereas adherence occurs when the microbe initially attaches.
Colonization occurs when transient microbes are on a tissue, whereas adherence is a more permanent attachment to cells.
C
192
Septicemia is an example of
a systemic infection.
a localized infection.
a transient infection.
an autoimmune infection.
A
193
Decalcification of the tooth enamel is caused by
dextrans.
lipopolysaccharide.
formic acid.
lactic acid.
D
194
The following bacterial genera are all implicated in dental caries EXCEPT
Fusobacterium.
Streptococcus.
Corynebacterium.
Borrelia.
D
195
Which of the following is an important factor in the development of dental caries?
high acid diet
low salt diet
high sugar diet
high salt diet
C
196
The spread of pathogens through the blood and lymph systems that results in a bloodborne systemic infection is called
pathogenesis.
cancer.
bacteremia.
septicemia.
D
197
Which of the following does NOT affect pathogen growth?
availability of microbial nutrients
pH
temperature
All of these answer choices affect growth.
D
198
Which of the following is a reason that specific pathogens tend to infect specific tissues?
Microbes preferentially target external tissues, such as skin, as the environment is more favorable for their growth than inside the body.
There are chemical and physical differences between tissues.
Tissues with neutral pH are colonized but those with acidic or alkaline pH are not.
Some tissues have receptors for microbes, but others do not.
B
199
Epithelial cells lining the respiratory tract form a
impenetrable barrier to infection.
connective tissue layer.
mucous membrane.
dry and rigid barrier with tight junctions between cells.
C
200
The condition that results when some bacteria are shed in the bloodstream and distributed to distant parts of the body but do not reproduce in the blood is called
uremia.
erythemia.
septicemia.
bacteremia.
D
201
Microbes initially colonize teeth by attaching to lipids attached to the enamel.
True
False
F
202
Streptococcus mutans produces dextran to aid in attachment to tooth surfaces.
True
False
T
203
Invasion is the ability of a pathogen to enter into host cells or tissues, spread, and cause disease.
True
False
T
204
Hormones that are produced under stress boost normal immune responses and play a role in stress-mediated disease resistance.
True
False
F
205
Pathogen virulence NEVER changes throughout a host's life.
True
False
F
206
Pathogenicity is the ability
of the host to resist damage by the pathogen.
of the pathogen to inflict damage on the host.
of the host to inflict damage on the pathogen.
None of these are correct.
B
207
Capsules are particularly important for
allowing bacteria to become more phagocytic.
making bacteria more vulnerable to host defense mechanisms.
protecting bacteria from host defense mechanisms.
making bacteria less pathogenic.
C
208
The decrease or loss of virulence of a pathogen is referred to as
lethal dose.
aging.
attenuation.
disinfectivity.
ATTENUATION
209
It is thought that attenuation occurs especially in a laboratory setting because
pathogens lose virulence with age and survive longer in laboratory cultures.
patients can be treated with drugs that induce attenuation.
nonvirulent or weakly virulent mutants grow faster in laboratory media when there is no selective advantage to virulence.
there is selection for more virulent strains in the laboratory.
C
210
Which disease CANNOT be prevented via the use of a vaccine generated from an attenuated pathogen?
rubella
malaria
measles
mumps
MALARIA
211
Pathogenicity and virulence differ in that
pathogenicity only refers to pathogens, whereas virulence refers to any microbe that can cause an infection.
virulence refers to the overall ability of a microbe to cause disease, whereas pathogenicity refers to the ability of one microbe to cause disease relative to another.
virulence only refers to pathogens, whereas pathogenicity refers to any microbe that can cause an infection.
pathogenicity refers to the overall ability of a microbe to cause disease, whereas virulence refers to the ability of one microbe to cause disease relative to another.
D
212
The dose of an antigen that kills 50% of animals in a test group and is used to estimate the virulence of a pathogen is known as
Death rate-50.
LD50 (lethal dose50).
Antigen dose50.
Virulence-50.
B
213
Virulence refers to the overall ability of an organism to cause disease.
True
False
F
214
Streptococcus pneumonia strains with capsules were called smooth because of their appearance on plates.
True
False
T
215
Attenuated vaccines cause a weaker immune response than killed vaccines.
True
False
F
216
Vibrio cholerae is a highly virulent pathogen compared with the influenza virus.
True
False
F
217
Virulence genes may be located on mobile genetic elements.
True
False
T
218
Because malnutrition can make the immune system weaker, the number of Vibrio cholerae cells necessary to produce cholera in an exposed individual is drastically reduced in individuals with substantial malnutrition.
True
False
T
219
Salmonella species use ________ to facilitate attachment to gastrointestinal tissue.
antiphagocytic proteins
pili
siderophores
type I fimbriae
D
220
Siderophores are
molecules that aid directly in attachment to host cells.
inorganic molecules that help in active transport.
toxins that affect the gastrointestinal tract.
organic molecules that help pathogens take up iron.
D
221
Which of the following is a way to prevent attenuation and maintain virulence in a bacterium?
inoculating an animal with the bacterium
polymerase chain reaction (PCR)
laboratory subculture
antibiotic therapy
A
222
Which of the following is a major growth-limiting micronutrient that influences microbial growth?
iron
water
vitamin K
sugar
A
223
________ are microbial infections acquired by hospital patients with noninfectious diseases because they are compromised hosts.
Immunocompromised infections
Healthcare-associated infections
Pathogenic infections
Virulent infections
B
224
An opportunistic pathogen causes disease ONLY in the presence of normal host resistance.
True
False
F
224
Pathogenicity islands are clusters of genes for virulence factors that are located together on the bacterial chromosome.
True
False
T
225
Virulence factors in Salmonella include antiphagocytic proteins.
True
False
F
226
HIV infection causes immunosuppression because it causes the destruction of CD4 lymphocytes.
True
False
T
227
R plasmids help prevent the spread of virulence factors.
True
False
F
228
Staphylococcus aureus produces ________, leading to fibrin clots that protect them from attack by host cells.
coagulase
lipase
collagenase
amylase
A
229
Which genus produces hyaluronidase?
Shigella
Procholorococcus
Streptococcus
Mycobacterium
C
230
________ in saliva cleaves glycosidic linkages in the peptidoglycan that is present in bacterial cell walls, weakening the wall and potentially causing cell lysis.
Lysozyme
Mucus
Lipid A
Fibrin
A
231
Hyaluronidase worsens infection by causing damage to red blood cells.
True
False
F
232
Diphtheria toxin is
an AB toxin.
a cytolytic toxin.
a type of endotoxin.
a superantigen toxin.
A
233
Tetanus toxin causes
muscles to be unable to contract.
muscles to be unable to relax.
severe diarrhea.
hemolytic uremic syndrome.
B
234
Shiga toxin is an enterotoxin that is produced by
Escherichia coli O157:H7.
Shigella dysenteriae.
Vibrio cholerae.
Clostridium tetani.
B
235
Which of the following is NOT an example of an AB toxin?
shiga-like toxin
hemolysins
botulinum toxin
tetanus toxin
B
236
________ are toxic proteins released from the pathogen during normal growth.
Exotoxins
Endotoxins
Microtoxins
Macrotoxins
A
237
Which of the following is a category of exotoxin?
lipophilic toxin
α-toxin
β-toxin
cytolytic toxin
D
238
Cholera begins following a bite from a mosquito.
True
False
F
239
Clostridium botulinum are endospore-forming bacteria normally found in the soil.
True
False
T
240
Diphtheria toxin inactivates elongation factor 2 by catalyzing the attachment of adenosine diphosphate ribose from NAD+.
True
False
T
241
Clostridium botulinum cannot produce toxins in improperly preserved foods.
True
False
F
242
Staphylococcus aureus and Streptococcus pyogenes strains can produce ________ that cause(s) the severe and sometimes life-threatening symptoms of toxic shock syndrome.
endotoxin
cytolytic
superantigen toxins
AB toxins
C
243
The α-toxin of Clostridium perfringens is
a superantigen toxin.
an endotoxin.
a lecithinase.
an enterotoxin.
C
244
Which of the following hemolysins is a phospholipase?
leukocidin
lecithinase
streptolysin-O
Staphylococcal α-toxin
B
245
Cytolytic toxins
are extracellular proteins that cause cell lysis and death by damaging the host cytoplasmic membrane.
are extracellular proteins.
damage host cytoplasmic membrane.
cause cell lysis and death.
A
246
Compared with an endotoxin, would a bacterial exotoxin generally be more likely to function after it had been significantly heated?
No, because exotoxins are carbohydrates and endotoxins are proteins.
Yes, because exotoxins are proteins and nonliving but endotoxins are part of the bacterial cell wall.
Yes, because exotoxins are very heat stable compared to endotoxins.
No, because exotoxins are heat-labile and less resistant to heating than endotoxins.
D
247
Which of the following is NOT a subunit of lipopolysaccharide (LPS)?
O-specific polysaccharide
core polysaccharide
M protein
lipid A
M PROTEIN
248
Exotoxins are ________, but endotoxins are ________.
carbohydrates / proteins
lipids / proteins
lipopolysaccharide-lipoprotein complexes / proteins
proteins / lipopolysaccharide-lipoprotein complexes
D
249
The toxic lipopolysaccharides produced by most gram-negative bacteria are called exotoxins.
True
False
F
250
Endotoxins are released in large amounts only when cells lyse.
True
False
T
251
The Limulus amebocyte lysate assay is used to detect endotoxin in clinical samples such as serum or cerebrospinal fluid.
True
False
T
252
Gram-positive bacteria produce endotoxins.
True
False
F
