ESTUDYR
BIO250 - STRAIGHTERLINE MICROBIOLOGY STUDY SET FINAL EXAM UPDATED
WITH MOST TESTED QUESTIONS AND ANSWERS | GRADED A+ | ASSURED
SUCCESS WITH DETAILED RATIONALES
1. What microbial process was responsible for changing Earth’s atmosphere from one without oxygen
to one with oxygen?
A. Anaerobic respiration
B. Methanogenesis
C. Oxygenic photosynthesis (✔ )
D. Nitrogen fixation
Rationale: Cyanobacteria and other photosynthetic microbes produced O₂ via oxygenic photosynthesis,
altering the atmosphere.
2. In the nitrogen cycle, which phase involves the release of nitrogen gas (N₂)?
A. Nitrogen fixation
B. Nitrification
C. Denitrification (✔ )
D. Ammonification
Rationale: Denitrifying bacteria convert nitrate (NO₃⁻) back to N₂ under anaerobic conditions.
3. In secondary wastewater treatment, why is air injected into the sludge during mixing and
recirculation?
A. To remove odors
B. To settle solids
C. To supply oxygen for aerobic bioremediators (✔ )
D. To sterilize pathogens
Rationale: Aerobic microbes require dissolved O₂ to degrade organic matter in sludge.
4. Which microorganism is used to make yogurt?
A. Saccharomyces cerevisiae
B. Escherichia coli
,ESTUDYR
C. Lactobacillus bulgaricus (✔ )
D. Streptococcus pneumoniae
Rationale: Yogurt cultures use L. bulgaricus (and S. thermophilus) to ferment lactose into lactic acid.
5. ATP is a:
A. Lipid that stores energy
B. Polysaccharide that stores glucose
C. Nucleotide that releases and stores cellular energy (✔ )
D. Protein that catalyzes reactions
Rationale: ATP’s phosphate bonds store energy used in metabolic processes.
6. A viral capsid is composed of:
A. Lipids
B. Carbohydrates
C. Proteins (✔ )
D. Nucleic acids
Rationale: Capsid proteins (capsomeres) assemble to protect viral genomes.
7. Which of these is not considered a living organism?
A. Bacteria
B. Archaea
C. Viruses (✔ )
D. Eukaryotic protists
Rationale: Viruses lack cellular structure and metabolic machinery, requiring hosts to replicate.
8. The order in which different types of RNA are involved in translation is:
A. tRNA → rRNA → mRNA
B. rRNA → mRNA → tRNA
C. mRNA → tRNA → rRNA (✔ )
D. mRNA → rRNA → tRNA
, ESTUDYR
Rationale: mRNA provides the template; tRNA brings amino acids; rRNA forms the ribosomal machinery.
9. Which bacterial identification technique, when positive, stains bacteria two contrasting colors?
A. Acid-fast staining
B. Capsule staining
C. Gram staining (✔ )
D. Endospore staining
Rationale: Gram-positive bacteria retain crystal violet (purple); Gram-negative take up safranin (pink).
10. Which structure is found in some, but not all, groups of eukaryotic microorganisms?
A. Nucleus
B. Mitochondria
C. Ribosomes
D. Cell wall (✔ )
Rationale: Many protists lack rigid cell walls; plants and fungi have them.
11. You’d consult Bergey’s Manual of Systematic Bacteriology rather than the Determinative Manual
to:
A. Identify unknown bacteria
B. Choose culture media
C. Investigate genetic and evolutionary relationships (✔ )
D. Determine antibiotic susceptibilities
Rationale: The Systematic Manual covers taxonomy and phylogeny.
12. Which structure is found in Gram-negative bacteria but absent in Gram-positive bacteria?
A. Thick peptidoglycan layer
B. Teichoic acids
C. Peptidoglycan cross-bridges
D. Outer lipid membrane (✔ )
Rationale: Gram-negative cells have an additional outer membrane containing lipopolysaccharides.
BIO250 - STRAIGHTERLINE MICROBIOLOGY STUDY SET FINAL EXAM UPDATED
WITH MOST TESTED QUESTIONS AND ANSWERS | GRADED A+ | ASSURED
SUCCESS WITH DETAILED RATIONALES
1. What microbial process was responsible for changing Earth’s atmosphere from one without oxygen
to one with oxygen?
A. Anaerobic respiration
B. Methanogenesis
C. Oxygenic photosynthesis (✔ )
D. Nitrogen fixation
Rationale: Cyanobacteria and other photosynthetic microbes produced O₂ via oxygenic photosynthesis,
altering the atmosphere.
2. In the nitrogen cycle, which phase involves the release of nitrogen gas (N₂)?
A. Nitrogen fixation
B. Nitrification
C. Denitrification (✔ )
D. Ammonification
Rationale: Denitrifying bacteria convert nitrate (NO₃⁻) back to N₂ under anaerobic conditions.
3. In secondary wastewater treatment, why is air injected into the sludge during mixing and
recirculation?
A. To remove odors
B. To settle solids
C. To supply oxygen for aerobic bioremediators (✔ )
D. To sterilize pathogens
Rationale: Aerobic microbes require dissolved O₂ to degrade organic matter in sludge.
4. Which microorganism is used to make yogurt?
A. Saccharomyces cerevisiae
B. Escherichia coli
,ESTUDYR
C. Lactobacillus bulgaricus (✔ )
D. Streptococcus pneumoniae
Rationale: Yogurt cultures use L. bulgaricus (and S. thermophilus) to ferment lactose into lactic acid.
5. ATP is a:
A. Lipid that stores energy
B. Polysaccharide that stores glucose
C. Nucleotide that releases and stores cellular energy (✔ )
D. Protein that catalyzes reactions
Rationale: ATP’s phosphate bonds store energy used in metabolic processes.
6. A viral capsid is composed of:
A. Lipids
B. Carbohydrates
C. Proteins (✔ )
D. Nucleic acids
Rationale: Capsid proteins (capsomeres) assemble to protect viral genomes.
7. Which of these is not considered a living organism?
A. Bacteria
B. Archaea
C. Viruses (✔ )
D. Eukaryotic protists
Rationale: Viruses lack cellular structure and metabolic machinery, requiring hosts to replicate.
8. The order in which different types of RNA are involved in translation is:
A. tRNA → rRNA → mRNA
B. rRNA → mRNA → tRNA
C. mRNA → tRNA → rRNA (✔ )
D. mRNA → rRNA → tRNA
, ESTUDYR
Rationale: mRNA provides the template; tRNA brings amino acids; rRNA forms the ribosomal machinery.
9. Which bacterial identification technique, when positive, stains bacteria two contrasting colors?
A. Acid-fast staining
B. Capsule staining
C. Gram staining (✔ )
D. Endospore staining
Rationale: Gram-positive bacteria retain crystal violet (purple); Gram-negative take up safranin (pink).
10. Which structure is found in some, but not all, groups of eukaryotic microorganisms?
A. Nucleus
B. Mitochondria
C. Ribosomes
D. Cell wall (✔ )
Rationale: Many protists lack rigid cell walls; plants and fungi have them.
11. You’d consult Bergey’s Manual of Systematic Bacteriology rather than the Determinative Manual
to:
A. Identify unknown bacteria
B. Choose culture media
C. Investigate genetic and evolutionary relationships (✔ )
D. Determine antibiotic susceptibilities
Rationale: The Systematic Manual covers taxonomy and phylogeny.
12. Which structure is found in Gram-negative bacteria but absent in Gram-positive bacteria?
A. Thick peptidoglycan layer
B. Teichoic acids
C. Peptidoglycan cross-bridges
D. Outer lipid membrane (✔ )
Rationale: Gram-negative cells have an additional outer membrane containing lipopolysaccharides.
