BIOS 242 MICROBIOLOGY
COMPREHENSIVE EXAM PREP
QUESTIONS AND ANSWERS
1. Which of the following components is unique to the cell walls of Acid-Fast bacteria, such as
Mycobacterium tuberculosis?
A. Teichoic acid
B. Mycolic acid
C. Lipopolysaccharide
D. Pseudomurein
Answer: B
Conceptual Explanation: Mycolic acids are long-chain fatty acids found in the cell walls of
the Mysobacteriaceae family, providing resistance to chemical damage and dehydration.
2. In the Gram staining procedure, what is the specific role of Gram’s Iodine?
A. Mordant
B. Decolorizing agent
C. Counterstain
,D. Primary stain
Answer: A
Conceptual Explanation: Gram’s Iodine acts as a mordant by forming a large CV-I complex
with crystal violet, which becomes trapped within the thick peptidoglycan layer of Gram-
positive cells.
3. Which enzyme is responsible for synthesizing a short RNA sequence to provide a 3’-OH
group for DNA polymerase during replication?
A. Helicase
B. DNA Ligase
C. Primase
D. Topoisomerase
Answer: C
Conceptual Explanation: Primase is an RNA polymerase that creates an RNA primer; DNA
polymerase III requires this free 3’-OH group to begin adding DNA nucleotides.
4. A bacterium that grows optimally at human body temperature (37 degrees Celsius) is
classified as a:
A. Psychrophile
B. Thermophile
C. Hyperthermophile
, D. Mesophile
Answer: D
Conceptual Explanation: Mesophiles have an optimal growth temperature range between
20 and 45 degrees Celsius, which includes human body temperature.
5. Which metabolic pathway produces the most ATP molecules per molecule of glucose in an
aerobic environment?
A. Glycolysis
B. Electron Transport Chain
C. Krebs Cycle
D. Fermentation
Answer: B
Conceptual Explanation: The Electron Transport Chain, through oxidative
phosphorylation, generates approximately 32-34 ATP per glucose molecule, significantly
more than other pathways.
6. Which of the following describes the mechanism of action for Penicillin?
A. Inhibition of protein synthesis at the 30S ribosome
B. Inhibition of peptidoglycan cross-linking
C. Disruption of the plasma membrane
D. Inhibition of RNA polymerase
COMPREHENSIVE EXAM PREP
QUESTIONS AND ANSWERS
1. Which of the following components is unique to the cell walls of Acid-Fast bacteria, such as
Mycobacterium tuberculosis?
A. Teichoic acid
B. Mycolic acid
C. Lipopolysaccharide
D. Pseudomurein
Answer: B
Conceptual Explanation: Mycolic acids are long-chain fatty acids found in the cell walls of
the Mysobacteriaceae family, providing resistance to chemical damage and dehydration.
2. In the Gram staining procedure, what is the specific role of Gram’s Iodine?
A. Mordant
B. Decolorizing agent
C. Counterstain
,D. Primary stain
Answer: A
Conceptual Explanation: Gram’s Iodine acts as a mordant by forming a large CV-I complex
with crystal violet, which becomes trapped within the thick peptidoglycan layer of Gram-
positive cells.
3. Which enzyme is responsible for synthesizing a short RNA sequence to provide a 3’-OH
group for DNA polymerase during replication?
A. Helicase
B. DNA Ligase
C. Primase
D. Topoisomerase
Answer: C
Conceptual Explanation: Primase is an RNA polymerase that creates an RNA primer; DNA
polymerase III requires this free 3’-OH group to begin adding DNA nucleotides.
4. A bacterium that grows optimally at human body temperature (37 degrees Celsius) is
classified as a:
A. Psychrophile
B. Thermophile
C. Hyperthermophile
, D. Mesophile
Answer: D
Conceptual Explanation: Mesophiles have an optimal growth temperature range between
20 and 45 degrees Celsius, which includes human body temperature.
5. Which metabolic pathway produces the most ATP molecules per molecule of glucose in an
aerobic environment?
A. Glycolysis
B. Electron Transport Chain
C. Krebs Cycle
D. Fermentation
Answer: B
Conceptual Explanation: The Electron Transport Chain, through oxidative
phosphorylation, generates approximately 32-34 ATP per glucose molecule, significantly
more than other pathways.
6. Which of the following describes the mechanism of action for Penicillin?
A. Inhibition of protein synthesis at the 30S ribosome
B. Inhibition of peptidoglycan cross-linking
C. Disruption of the plasma membrane
D. Inhibition of RNA polymerase
