MICROBIOLOGY COMPREHENSIVE
FINAL EXAM QUESTIONS AND
ANSWERS
1. Which component of the bacterial cell wall is specifically targeted by lysozyme?
A. The peptide cross-bridges of the peptidoglycan
B. The lipopolysaccharide layer in Gram-negative bacteria
C. The glycosidic bonds between NAG and NAM
D. The teichoic acids in Gram-positive bacteria
Answer: C
Conceptual Explanation: Lysozyme breaks the beta-1,4-glycosidic bonds between N-
acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) in the peptidoglycan backbone.
2. In the Gram stain procedure, what is the specific role of the alcohol-acetone solution?
A. To serve as a mordant to fix the dye
B. To stain the background for contrast
C. To dissolve the outer membrane and dehydrate the peptidoglycan layer
,D. To act as a primary stain for all bacterial cells
Answer: C
Conceptual Explanation: The decolorizer (alcohol-acetone) dissolves the lipid-rich outer
membrane of Gram-negative cells and dehydrates the thick peptidoglycan of Gram-positive
cells to trap the crystal violet-iodine complex.
3. Which of the following describes a bacterium that requires oxygen but at concentrations
lower than those found in the atmosphere?
A. Facultative anaerobe
B. Aerotolerant anaerobe
C. Obligate aerobe
D. Microaerophile
Answer: D
Conceptual Explanation: Microaerophiles require oxygen for survival but are inhibited by
high concentrations of oxygen found in normal atmospheric air.
4. During which phase of the bacterial growth curve are cells most metabolically active and
sensitive to antibiotics?
A. Log phase
B. Lag phase
C. Stationary phase
, D. Death phase
Answer: A
Conceptual Explanation: The log (exponential) phase is characterized by rapid cell
division and high metabolic activity, making them most susceptible to drugs like penicillin
that target cell wall synthesis.
5. What is the net gain of ATP molecules produced per molecule of glucose during glycolysis
in a prokaryotic cell?
A. 2 ATP
B. 4 ATP
C. 36 ATP
D. 38 ATP
Answer: A
Conceptual Explanation: While 4 ATP are produced total, 2 ATP are consumed in the
preparatory stage, resulting in a net gain of 2 ATP molecules.
6. Which enzyme is responsible for synthesizing a short RNA primer to initiate DNA
replication?
A. DNA polymerase III
B. Helicase
C. Primase
FINAL EXAM QUESTIONS AND
ANSWERS
1. Which component of the bacterial cell wall is specifically targeted by lysozyme?
A. The peptide cross-bridges of the peptidoglycan
B. The lipopolysaccharide layer in Gram-negative bacteria
C. The glycosidic bonds between NAG and NAM
D. The teichoic acids in Gram-positive bacteria
Answer: C
Conceptual Explanation: Lysozyme breaks the beta-1,4-glycosidic bonds between N-
acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) in the peptidoglycan backbone.
2. In the Gram stain procedure, what is the specific role of the alcohol-acetone solution?
A. To serve as a mordant to fix the dye
B. To stain the background for contrast
C. To dissolve the outer membrane and dehydrate the peptidoglycan layer
,D. To act as a primary stain for all bacterial cells
Answer: C
Conceptual Explanation: The decolorizer (alcohol-acetone) dissolves the lipid-rich outer
membrane of Gram-negative cells and dehydrates the thick peptidoglycan of Gram-positive
cells to trap the crystal violet-iodine complex.
3. Which of the following describes a bacterium that requires oxygen but at concentrations
lower than those found in the atmosphere?
A. Facultative anaerobe
B. Aerotolerant anaerobe
C. Obligate aerobe
D. Microaerophile
Answer: D
Conceptual Explanation: Microaerophiles require oxygen for survival but are inhibited by
high concentrations of oxygen found in normal atmospheric air.
4. During which phase of the bacterial growth curve are cells most metabolically active and
sensitive to antibiotics?
A. Log phase
B. Lag phase
C. Stationary phase
, D. Death phase
Answer: A
Conceptual Explanation: The log (exponential) phase is characterized by rapid cell
division and high metabolic activity, making them most susceptible to drugs like penicillin
that target cell wall synthesis.
5. What is the net gain of ATP molecules produced per molecule of glucose during glycolysis
in a prokaryotic cell?
A. 2 ATP
B. 4 ATP
C. 36 ATP
D. 38 ATP
Answer: A
Conceptual Explanation: While 4 ATP are produced total, 2 ATP are consumed in the
preparatory stage, resulting in a net gain of 2 ATP molecules.
6. Which enzyme is responsible for synthesizing a short RNA primer to initiate DNA
replication?
A. DNA polymerase III
B. Helicase
C. Primase
