Sem 3 BRS Micro - General Properties Of Microorganisms; /Bacteria
- 1.
A pharmaceutical company has developed a new compound that is well tolerated by the body and inhibits the sterol ergo sterol synthesis. Screening of anti-infectious agent activity should be directed toward
- A.
Bacteria
- B.
Chlamydia species
- C.
Fungi
- D.
Rickettsia species
- E.
Viruses
Correct Answer
C. FungiExplanation
Fungi have ergo sterol as their dominant membrane sterol. Mycoplasmas are the only prokaryotes with sterols in their cytoplasmic membrane, but they do not synthesize their own sterols.Rate this question:
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- 2.
50S ribosomal subunits are found in
- A.
Bacteria
- B.
Fungi
- C.
Prions
- D.
Protozoa
- E.
Viruses
Correct Answer
A. BacteriaExplanation
Bacteria have70S ribosomes composed of 30S and 50S subunits. Fungi and protozoa have 80S ribosomes, and prions and viruses do not have ribosomes.Rate this question:
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- 3.
The normal flora of the large intestine consists mainly of
- A.
Bacteria
- B.
Fungi
- C.
Protozoa
- D.
Viruses
- E.
No microbial agents
Correct Answer
A. BacteriaExplanation
Bacteria form the majority of the normal flora of the large intestine. Other types of human infectious agents are not usually present except in time of disease.Rate this question:
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- 4.
The minimal concentration of alcohol necessary to kill bacteria and enveloped viruses is
- A.
30%
- B.
40%
- C.
50%
- D.
60%
- E.
70%
Correct Answer
E. 70%Explanation
An alcohol concentration of 70% to 95% is necessary to kill bacteriaRate this question:
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- 5.
Human obligate intracellular pathogens that depend on the host cell for ATP production are
- A.
Bacteriophages
- B.
Mycoplasma species
- C.
Prions
- D.
Rickettsia species
- E.
Viroids
Correct Answer
D. Rickettsia speciesExplanation
Chlamydia and rickettsia are obligate intracellular pathogens because they depend on the host cell
to provide them with ATP.Rate this question:
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- 6.
Dimorphism is a characteristic of
- A.
Bacteria
- B.
Fungi
- C.
Prions
- D.
Rickettsia species
- E.
Viruses
Correct Answer
B. FungiExplanation
Certain species of pathogenic fungi are dimorphic (i.e., existing as yeast or mold forms depending
on their environment).Rate this question:
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- 7.
A new infectious agent has been isolated from deer ticks. It lacks a cell wall but has 70S ribosomes. This agent is most likely a
- A.
Bacterium
- B.
Chlamydia species
- C.
Mycoplasma species
- D.
Rickettsia species
- E.
Virus
Correct Answer
C. Mycoplasma speciesExplanation
The correct answer is Mycoplasma species. Mycoplasma species are unique bacteria that lack a cell wall, making them resistant to antibiotics that target cell wall synthesis. They also have 70S ribosomes, which are characteristic of bacteria. Chlamydia species and Rickettsia species are also bacteria, but they have cell walls. Viruses are not considered bacteria and do not possess ribosomes.Rate this question:
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- 8.
Chapter 2 BACTERIA A bacterial toxin with super antigen activity is produced by
- A.
Clostridia tetani
- B.
Bordetella pertussis
- C.
Escherichia coli
- D.
Staphylococcus aureus
- E.
Vibrio cholera
Correct Answer
D. Staphylococcus aureusExplanation
Staphylococcus aureus produces an enterotoxin and TSST-1 toxins with super-antigen activity.
Streptococcus pyogenes also produces toxins with this activity.Rate this question:
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- 9.
Sugar transport into bacteria is frequently facilitated by
- A.
Acetyl transferase
- B.
Neuraminidases
- C.
Oxidases
- D.
Penicillin-binding proteins
- E.
Phospho transferases
Correct Answer
E. Phospho transferasesExplanation
The transport of sugar into a bacterium frequently involves the transfer of a phosphate group to the s
ugar molecule.Rate this question:
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- 10.
Thayer-Martin and Martin-Lewis media are used to isolate and identify E. coli
- A.
E. coli
- B.
Mycobacteria
- C.
Neisseria
- D.
Salmonella
- E.
Shigella
Correct Answer
C. NeisseriaExplanation
These media are variants of chocolate agar and contain antibiotics that inhibit many normal respiratory
and genital bacteria but allow the growth of Neisseria species.Rate this question:
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- 11.
B-lactamases confer antibiotic resistance by
- A.
Altering antibiotic permeability
- B.
Altering penicillin-binding proteins
- C.
Altering 70S ribosome structure
- D.
Modifying cellular RNA polymerase
- E.
Modifying antibiotic structure
Correct Answer
E. Modifying antibiotic structureExplanation
B-lactamases cleave the b-lactam ring structure that is important for the antibacterial activity of penicillins,
cephalosporins, monobactams, and carbapenems.Rate this question:
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- 12.
Polymers of N-acetyl glucosamine and N-acetyl muramic acid are found in which of the following structures?
- A.
Teichoic acid
- B.
Cell wall
- C.
Glycocalyx
- D.
Lipopolysaccharide
Correct Answer
B. Cell wallExplanation
N-acetyl glucosamine and N-acetyl muramic acid are polymerized to form the peptidoglycan backbone of the cell wall.Rate this question:
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- 13.
A phage that is not inactivated by proteases is called a
- A.
Prophage
- B.
Virulent phage
- C.
Temperate phage
- D.
Filamentous phage
Correct Answer
A. ProphageExplanation
A prophage is the intracellular DNA of a phage and is therefore resistant to protease degradation.Rate this question:
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- 14.
Bacteria that synthesize organic compounds from inorganic compounds are
- A.
Heterotrophs
- B.
Obligate anaerobes
- C.
Aerobes
- D.
Facultative anaerobes
- E.
Autotrophs
Correct Answer
E. AutotrophsExplanation
Autotrophic bacteria do not require organic compounds for growth because they synthesize them
from inorganic precursors.Rate this question:
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- 15.
A bacterial structure involved in adherence is
- A.
Capsule
- B.
Lipopolysaccharide
- C.
Ordinary pili
- D.
O-specific side-chain
- E.
Teichoic acid
Correct Answer
C. Ordinary piliExplanation
Ordinary pili, adhesins, and the glycocalyx are three bacterial structures that are involved in adherence.Rate this question:
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- 16.
Aminoglycoside antibiotics are
- A.
Bactericidal for Gram-positive bacteria
- B.
Inactivated by R-factor phosphor transferases
- C.
Mycolic acid synthesis inhibitors
- D.
Peptidoglycan synthesis inhibitors
- E.
Require bacterial growth for the effect
Correct Answer
E. Require bacterial growth for the effectExplanation
Bacteria must be actively replicating and synthesizing protein for these compounds, which bind
to the 30S ribosomal subunit to have their bactericidal effect.Rate this question:
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- 17.
A-B subunit structure as it relates to bacterial pathogenesis refers to the structure of
- A.
Bacterial exotoxins
- B.
Gram-negative bacteria endotoxin
- C.
Nucleic acid inhibitor antibiotics
- D.
Penicillin-binding proteins
- E.
Resistance transfer factors
Correct Answer
A. Bacterial exotoxinsExplanation
Many bacterial exotoxins have an A-B subunit structure in which the B subunit is involved in binding
and the A subunit possesses biological activity inside the affected cell.Rate this question:
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- 18.
Which of the following displays the Pasteur effect?
- A.
Heterotrophs
- B.
Obligate anaerobes
- C.
Aerobes
- D.
Facultative anaerobes
- E.
Autotrophs
Correct Answer
D. Facultative anaerobesExplanation
Facultative anaerobes shift from a fermentative to a respiratory metabolism in the presence of
air because the energy needs of the cell are met by consuming less glucose (Pasteur Effect) under respiratory metabolism.Rate this question:
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- 19.
Which of the following toxins acts on synaptosomes?
- A.
E. coli heat-labile toxin
- B.
Clostridium tetani exotoxin
- C.
Corynebacterium diphtheria exotoxin
- D.
Pseudomonas aeruginosa exotoxin
- E.
Clostridium perfringens alpha-toxin
Correct Answer
B. Clostridium tetani exotoxinExplanation
Clostridium tetani Exotoxin acts on synaptosomes, thereby causing hyper-reflexia of skeletal muscles.Rate this question:
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- 20.
Superoxide dismutase-containing bacteria
- A.
Need superoxide to grow
- B.
Are frequently obligate anaerobes
- C.
Grow slowly in the presence of CO2
- D.
Produce hydrogen peroxide from hydrogen ion and the superoxide free radical (O2-)
Correct Answer
D. Produce hydrogen peroxide from hydrogen ion and the superoxide free radical (O2-)Explanation
Superoxide dismutase is found in aerobic and facultative anaerobic bacteria. It protects them from
the toxic free radical (O2-) by combining it with a hydrogen ion to form hydrogen peroxide, which is
subsequently degraded by peroxidase.Rate this question:
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- 21.
Lysogenic phage conversion involves
- A.
The transformation of a virulent phage to a lysogenic phage
- B.
A change in bacterial phenotype due to the presence of a prophage
- C.
The conversion of a prophage to a temperate phage
- D.
The incorporation of a prophage into the bacterial chromosome
Correct Answer
B. A change in bacterial phenotype due to the presence of a prophageExplanation
Lysogenic phage conversion refers to the process in which a bacterial phenotype changes as a result of the presence of a prophage. A prophage is a viral genome that has integrated into the bacterial chromosome and remains dormant until it is activated. When the prophage is activated, it can cause changes in the bacterial phenotype, such as the production of toxins or other virulence factors. This change in phenotype is the result of the expression of genes carried by the prophage, which can alter the behavior or characteristics of the bacterial host.Rate this question:
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- 22.
Bacteria capable of growth in a high salt concentration are best isolated in which of the following media?
- A.
Minimal growth media
- B.
Complex growth media
- C.
Differential growth media
- D.
Selective growth media
Correct Answer
D. Selective growth mediaExplanation
A selective growth medium that contains a high salt concentration would permit bacterial growth.Rate this question:
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- 23.
Bacteria lacking superoxide dismutase are
- A.
Heterotrophs
- B.
Obligate anaerobes
- C.
Aerobes
- D.
Facultative anaerobes
- E.
Autotrophs
Correct Answer
B. Obligate anaerobesExplanation
Superoxide dismutase, which is present in aerobes and facultative anaerobe organisms, protects them
from the toxic O2- radical. This enzyme is not present in obligate anaerobes.Rate this question:
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- 24.
The regulation of enzyme activity in bacterial cells can
- A.
Be coupled to the binding of effector molecules
- B.
Be controlled by a catabolite activator protein(CAP)
- C.
Occur via attenuation sequences
- D.
Involve inducer molecules
Correct Answer
A. Be coupled to the binding of effector moleculesExplanation
The biochemical activity of an enzyme may be regulated by binding of effect or molecules or by
biosynthetic pathway end-product feedback inhibition. Enzyme synthesis may be controlled by inducers,
attenuation sequences, or catabolite activator protein.Rate this question:
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- 25.
The plasma membrane
- A.
Contains matrix porins
- B.
Includes endotoxin
- C.
Contains glycocalyx
- D.
Contains the enzymes involved in bacterial oxidative phosphorylation
Correct Answer
D. Contains the enzymes involved in bacterial oxidative phosphorylationExplanation
The plasma membrane contains the enzymes involved in oxidative phosphorylationRate this question:
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- 26.
Bacterial antibiotic resistance is frequently conveyed by
- A.
A temperate bacteriophage
- B.
An R-factor plasmid
- C.
A replicon
- D.
A lytic bacteriophage
- E.
An intron
Correct Answer
B. An R-factor plasmidExplanation
R-factor (resistance) plasmids contain genes for proteins that degrade antibiotics or alter antibiotic
transport, thus conferring antibiotic resistance. They also carry transfer genes, which facilitate their
intercellular transfer to other genomes.Rate this question:
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- 27.
The expression of the lac operon
- A.
Must be initiated by the binding of an inducer protein
- B.
Involves the release of allolactose from a repressor protein
- C.
Does not involve the expression of structural genes
- D.
Necessitates the finding of RNA polymerase followed by transcription
Correct Answer
A. Must be initiated by the binding of an inducer proteinExplanation
The transcription of the lac operon is under negative control. Initiation depends on the binding of
allolactose to a repressor protein. This reaction prevents the repressor from binding to the operator
region, thus allowing RNA polymerase to bind and transcription to proceed.Rate this question:
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- 28.
Bacteriophage containing host-cell DNA is involved in which of the following processes?
- A.
Transformation
- B.
Conjugation
- C.
Transduction
- D.
Transcription
- E.
Recombination
Correct Answer
C. TransductionExplanation
Bacteriophages containing portions of host-cell DNA can introduce this genetic material into new host cells via the process of transduction.Rate this question:
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- 29.
The exchange of allelic forms of genes is involved in which of the following processes?
- A.
Transformation
- B.
Conjugation
- C.
Transduction
- D.
Transcription
- E.
Recombination
Correct Answer
E. RecombinationExplanation
DNA or genetic recombination is the general term used to describe the exchange of allelic forms
of genes in bacteria or eukaryotic cells.Rate this question:
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- 30.
Which of the following processes creates high-frequency recombination donors?
- A.
Transformation
- B.
Conjugation
- C.
Transduction
- D.
Transcription
- E.
Recombination
- F.
Translation
Correct Answer
E. RecombinationExplanation
High-frequency recombination donors, which result from the integration of a fertility (F) factor in to
chromosomal DNA, are created by recombination.Rate this question:
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Jan 18, 2023Quiz Edited by
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