BIOS 242 MICROBIOLOGY WEEK 2
QUIZ - COMPREHENSIVE ASSESSMENT
QUESTIONS AND ANSWERS
1. Which of the following cellular components is unique to Gram-positive bacteria and
functions to provide cell wall stability and an antigenic determinant?
A. Lipopolysaccharide (LPS)
B. Teichoic acids
C. Periplasmic space
D. Outer membrane proteins
Answer: B
Conceptual Explanation: Teichoic acids are found exclusively in the thick peptidoglycan
layer of Gram-positive bacteria, whereas LPS and the outer membrane are characteristic of
Gram-negative bacteria.
2. In the Gram staining procedure, what is the specific role of the decolorizer
(alcohol/acetone)?
A. It acts as a primary stain for Gram-negative cells.
,B. It dissolves the lipids in the outer membrane of Gram-negative cells, allowing the
primary stain to escape.
C. It forms a complex with crystal violet to trap it in the cell.
D. It increases the affinity of the cell wall for the counterstain.
Answer: B
Conceptual Explanation: Decolorizer damages the thin peptidoglycan and lipid-rich outer
membrane of Gram-negative cells, allowing the crystal violet-iodine complex to wash out.
3. Which metabolic pathway produces the highest net yield of ATP per molecule of glucose in
a prokaryotic cell?
A. Fermentation
B. Glycolysis
C. Aerobic Electron Transport Chain
D. The Krebs Cycle
Answer: C
Conceptual Explanation: Aerobic respiration via the Electron Transport Chain (ETC) and
oxidative phosphorylation produces approximately 34 ATP, compared to 2 from glycolysis
or fermentation.
4. A bacteria that requires a high concentration of salt to grow is known as a(n):
A. Acidophile
, B. Facultative anaerobe
C. Mesophile
D. Obligate halophile
Answer: D
Conceptual Explanation: Halophiles are ‘salt-loving’ organisms; obligate halophiles
require high osmotic pressure (high salt) to survive.
5. During which phase of the bacterial growth curve are the bacteria most susceptible to
antibiotics like penicillin?
A. Lag phase
B. Log (Exponential) phase
C. Stationary phase
D. Death phase
Answer: B
Conceptual Explanation: Penicillin targets cell wall synthesis. Bacteria are most actively
synthesizing cell walls during the Log phase, making them highly vulnerable.
6. What is the function of the bacterial endospore?
A. Reproduction and multiplication
B. Storage of excess nutrients
QUIZ - COMPREHENSIVE ASSESSMENT
QUESTIONS AND ANSWERS
1. Which of the following cellular components is unique to Gram-positive bacteria and
functions to provide cell wall stability and an antigenic determinant?
A. Lipopolysaccharide (LPS)
B. Teichoic acids
C. Periplasmic space
D. Outer membrane proteins
Answer: B
Conceptual Explanation: Teichoic acids are found exclusively in the thick peptidoglycan
layer of Gram-positive bacteria, whereas LPS and the outer membrane are characteristic of
Gram-negative bacteria.
2. In the Gram staining procedure, what is the specific role of the decolorizer
(alcohol/acetone)?
A. It acts as a primary stain for Gram-negative cells.
,B. It dissolves the lipids in the outer membrane of Gram-negative cells, allowing the
primary stain to escape.
C. It forms a complex with crystal violet to trap it in the cell.
D. It increases the affinity of the cell wall for the counterstain.
Answer: B
Conceptual Explanation: Decolorizer damages the thin peptidoglycan and lipid-rich outer
membrane of Gram-negative cells, allowing the crystal violet-iodine complex to wash out.
3. Which metabolic pathway produces the highest net yield of ATP per molecule of glucose in
a prokaryotic cell?
A. Fermentation
B. Glycolysis
C. Aerobic Electron Transport Chain
D. The Krebs Cycle
Answer: C
Conceptual Explanation: Aerobic respiration via the Electron Transport Chain (ETC) and
oxidative phosphorylation produces approximately 34 ATP, compared to 2 from glycolysis
or fermentation.
4. A bacteria that requires a high concentration of salt to grow is known as a(n):
A. Acidophile
, B. Facultative anaerobe
C. Mesophile
D. Obligate halophile
Answer: D
Conceptual Explanation: Halophiles are ‘salt-loving’ organisms; obligate halophiles
require high osmotic pressure (high salt) to survive.
5. During which phase of the bacterial growth curve are the bacteria most susceptible to
antibiotics like penicillin?
A. Lag phase
B. Log (Exponential) phase
C. Stationary phase
D. Death phase
Answer: B
Conceptual Explanation: Penicillin targets cell wall synthesis. Bacteria are most actively
synthesizing cell walls during the Log phase, making them highly vulnerable.
6. What is the function of the bacterial endospore?
A. Reproduction and multiplication
B. Storage of excess nutrients
