ADVANCED MICROBIOLOGY: BIOL 271
MODULE 1 EXAM QUESTIONS AND
ANSWERS
1. Which of the following describes the primary difference between the cytoplasmic
membranes of Bacteria and Archaea?
A. Bacteria contain hopanoids for stability, whereas Archaea utilize isoprene-based side
chains with ether linkages.
B. Archaea use ester-linked phospholipids, whereas Bacteria use ether-linked lipids.
C. Archaea have a phospholipid bilayer exclusively, whereas Bacteria may have
monolayers.
D. Bacterial membranes contain L-glycerol, while Archaeal membranes contain D-glycerol.
Answer: A
Conceptual Explanation: Bacterial membranes utilize ester-linked fatty acids and often
hopanoids. In contrast, Archaea utilize ether-linked isoprenoids, which can sometimes
form monolayers for extreme heat stability.
2. In fluorescence microscopy, what is the role of the dichroic mirror?
A. To reflect shorter wavelengths to the specimen and pass longer wavelengths to the
observer.
,B. To focus the electron beam onto the specimen.
C. To magnify the image before it reaches the ocular lens.
D. To polarize light to increase the contrast of living cells.
Answer: A
Conceptual Explanation: A dichroic mirror acts as a wavelength-selective filter, reflecting
the shorter excitation light toward the sample while allowing the longer-wavelength
emitted fluorescence to pass through to the detector.
3. Which enzyme is responsible for relieving torsional stress (supercoiling) ahead of the
replication fork in E. coli?
A. DNA Ligase
B. Primase
C. DNA Gyrase (Topoisomerase II)
D. DNA Polymerase I
Answer: C
Conceptual Explanation: DNA Gyrase introduces negative supercoils or removes positive
supercoils to prevent DNA from becoming overwound during replication.
4. What is the specific function of the 16S rRNA in the prokaryotic ribosome?
A. It contains the Shine-Dalgarno complementary sequence for initiation site recognition.
B. It facilitates the binding of the 50S and 30S subunits.
, C. It catalyzes the formation of the peptide bond.
D. It acts as the tRNA carrier for the P-site.
Answer: A
Conceptual Explanation: The 16S rRNA within the 30S subunit contains a sequence
complementary to the Shine-Dalgarno sequence on mRNA, ensuring proper alignment for
translation initiation.
5. During the process of endospore formation, which sigma factor is responsible for the early
gene expression in the mother cell?
A. Sigma E
B. Sigma F
C. Sigma G
D. Sigma K
Answer: A
Conceptual Explanation: Endospore formation involves a cascade of sigma factors; Sigma
E is the first factor activated in the mother cell compartment.
6. Calculate the resolution of a light microscope using a 100x objective (NA = 1.25) and a light
source of 500 nm.
A. 200 microns
B. 0.2 microns
MODULE 1 EXAM QUESTIONS AND
ANSWERS
1. Which of the following describes the primary difference between the cytoplasmic
membranes of Bacteria and Archaea?
A. Bacteria contain hopanoids for stability, whereas Archaea utilize isoprene-based side
chains with ether linkages.
B. Archaea use ester-linked phospholipids, whereas Bacteria use ether-linked lipids.
C. Archaea have a phospholipid bilayer exclusively, whereas Bacteria may have
monolayers.
D. Bacterial membranes contain L-glycerol, while Archaeal membranes contain D-glycerol.
Answer: A
Conceptual Explanation: Bacterial membranes utilize ester-linked fatty acids and often
hopanoids. In contrast, Archaea utilize ether-linked isoprenoids, which can sometimes
form monolayers for extreme heat stability.
2. In fluorescence microscopy, what is the role of the dichroic mirror?
A. To reflect shorter wavelengths to the specimen and pass longer wavelengths to the
observer.
,B. To focus the electron beam onto the specimen.
C. To magnify the image before it reaches the ocular lens.
D. To polarize light to increase the contrast of living cells.
Answer: A
Conceptual Explanation: A dichroic mirror acts as a wavelength-selective filter, reflecting
the shorter excitation light toward the sample while allowing the longer-wavelength
emitted fluorescence to pass through to the detector.
3. Which enzyme is responsible for relieving torsional stress (supercoiling) ahead of the
replication fork in E. coli?
A. DNA Ligase
B. Primase
C. DNA Gyrase (Topoisomerase II)
D. DNA Polymerase I
Answer: C
Conceptual Explanation: DNA Gyrase introduces negative supercoils or removes positive
supercoils to prevent DNA from becoming overwound during replication.
4. What is the specific function of the 16S rRNA in the prokaryotic ribosome?
A. It contains the Shine-Dalgarno complementary sequence for initiation site recognition.
B. It facilitates the binding of the 50S and 30S subunits.
, C. It catalyzes the formation of the peptide bond.
D. It acts as the tRNA carrier for the P-site.
Answer: A
Conceptual Explanation: The 16S rRNA within the 30S subunit contains a sequence
complementary to the Shine-Dalgarno sequence on mRNA, ensuring proper alignment for
translation initiation.
5. During the process of endospore formation, which sigma factor is responsible for the early
gene expression in the mother cell?
A. Sigma E
B. Sigma F
C. Sigma G
D. Sigma K
Answer: A
Conceptual Explanation: Endospore formation involves a cascade of sigma factors; Sigma
E is the first factor activated in the mother cell compartment.
6. Calculate the resolution of a light microscope using a 100x objective (NA = 1.25) and a light
source of 500 nm.
A. 200 microns
B. 0.2 microns
