BIOL 3200 Final Exam Actual Exam V3 | BIOL 3200 General
Microbiology (BIOL 3200 Final Exam) | Auburn University
1. Where is the lipopolysaccharide (LPS) layer located in a bacterial cell?
A. The periplasmic space of Gram-negative bacteria
B. The thick peptidoglycan layer of Gram-positive bacteria
C. The cytoplasmic membrane of all bacteria
D. The outer membrane of Gram-negative bacteria
Answer: D
Rationale: The lipopolysaccharide layer is a defining feature of the outer membrane in
Gram-negative bacteria. It consists of Lipid A, a core polysaccharide, and the O-specific
polysaccharide. Lipid A is particularly significant because it acts as an endotoxin,
potentially triggering a severe immune response in humans.
2. Which two sugars make up the glycan backbone of peptidoglycan?
A. N-acetylglucosamine and N-acetylmuramic acid
B. Glucose and Fructose
C. Ribose and Deoxyribose
D. Galactose and Mannose
Answer: A
Rationale: Peptidoglycan is composed of alternating units of N-acetylglucosamine (NAG)
and N-acetylmuramic acid (NAM). These units are linked by beta-1,4-glycosidic bonds to
form long glycan chains. The NAM residues are further cross-linked by short peptide chains
to provide structural integrity to the cell wall.
3. Bacterial flagella move the cell by which of the following mechanisms?
A. A whip-like back-and-forth motion
B. A rhythmic contraction of microtubule doublets
C. Rotation powered by the proton motive force
D. Gliding motility using slime secretion
Answer: C
Rationale: Unlike eukaryotic flagella, bacterial flagella function like a propeller and rotate
at high speeds. This rotation is powered by the flow of protons through the Mot protein
,complex in the cell membrane. The direction of rotation determines whether the bacterium
performs a run or a tumble.
4. Which specialized structure allows certain bacteria to survive extreme environmental
conditions like heat and radiation?
A. Endospore
B. Pili
C. Gas vesicles
D. Capsule
Answer: A
Rationale: Endospores are highly differentiated cells that are extremely resistant to heat,
harsh chemicals, and radiation. They are formed during a process called sporulation,
typically when nutrients become limited. Once favorable conditions return, the endospore
can germinate back into a vegetative cell.
5. Which transport system uses ATP to move solutes against a concentration gradient and is
common in both Bacteria and Archaea?
A. Group translocation
B. Simple diffusion
C. Facilitated diffusion
D. ABC transporters
Answer: D
Rationale: ATP-binding cassette (ABC) transporters are primary active transporters that
utilize ATP hydrolysis to move substrates across the membrane. These systems typically
consist of a periplasmic binding protein, a transmembrane channel, and an ATP-
hydrolyzing protein. They are highly specific and can transport nutrients even when they
are present at very low concentrations in the environment.
6. During which phase of the bacterial growth curve is the population growing at its
maximum rate?
A. Lag phase
B. Death phase
C. Stationary phase
D. Log (Exponential) phase
Answer: D
, Rationale: The log phase is characterized by cell doubling at a constant, maximum rate
given the environmental conditions. During this time, the metabolic activity is highest, and
the generation time is at its shortest. Researchers often use cells from this phase for
experiments because the population is most uniform.
7. Organisms that grow optimally at temperatures between 45°C and 80°C are classified as:
A. Psychrophiles
B. Mesophiles
C. Thermophiles
D. Hyperthermophiles
Answer: C
Rationale: Thermophiles are adapted to high-temperature environments, such as hot
springs or compost piles. Their proteins and membranes are specifically evolved to remain
stable and functional at temperatures that would denature most mesophilic organisms.
This stability is often due to increased ionic bonding and highly hydrophobic interiors of
their proteins.
8. Microorganisms that do not use oxygen for energy but are not harmed by its presence are
called:
A. Obligate aerobes
B. Microaerophiles
C. Obligate anaerobes
D. Aerotolerant anaerobes
Answer: D
Rationale: Aerotolerant anaerobes possess enzymes like superoxide dismutase or
peroxidase to neutralize toxic oxygen species. However, they rely exclusively on
fermentation or anaerobic respiration for energy production. This distinguishes them from
facultative anaerobes, which prefer using oxygen if it is available.
9. Which of the following describes a facultative anaerobe?
A. It grows only in the presence of oxygen.
B. It grows better with oxygen but can grow without it.
C. It is killed by the presence of oxygen.
D. It requires a specific low concentration of oxygen.
Answer: B
Microbiology (BIOL 3200 Final Exam) | Auburn University
1. Where is the lipopolysaccharide (LPS) layer located in a bacterial cell?
A. The periplasmic space of Gram-negative bacteria
B. The thick peptidoglycan layer of Gram-positive bacteria
C. The cytoplasmic membrane of all bacteria
D. The outer membrane of Gram-negative bacteria
Answer: D
Rationale: The lipopolysaccharide layer is a defining feature of the outer membrane in
Gram-negative bacteria. It consists of Lipid A, a core polysaccharide, and the O-specific
polysaccharide. Lipid A is particularly significant because it acts as an endotoxin,
potentially triggering a severe immune response in humans.
2. Which two sugars make up the glycan backbone of peptidoglycan?
A. N-acetylglucosamine and N-acetylmuramic acid
B. Glucose and Fructose
C. Ribose and Deoxyribose
D. Galactose and Mannose
Answer: A
Rationale: Peptidoglycan is composed of alternating units of N-acetylglucosamine (NAG)
and N-acetylmuramic acid (NAM). These units are linked by beta-1,4-glycosidic bonds to
form long glycan chains. The NAM residues are further cross-linked by short peptide chains
to provide structural integrity to the cell wall.
3. Bacterial flagella move the cell by which of the following mechanisms?
A. A whip-like back-and-forth motion
B. A rhythmic contraction of microtubule doublets
C. Rotation powered by the proton motive force
D. Gliding motility using slime secretion
Answer: C
Rationale: Unlike eukaryotic flagella, bacterial flagella function like a propeller and rotate
at high speeds. This rotation is powered by the flow of protons through the Mot protein
,complex in the cell membrane. The direction of rotation determines whether the bacterium
performs a run or a tumble.
4. Which specialized structure allows certain bacteria to survive extreme environmental
conditions like heat and radiation?
A. Endospore
B. Pili
C. Gas vesicles
D. Capsule
Answer: A
Rationale: Endospores are highly differentiated cells that are extremely resistant to heat,
harsh chemicals, and radiation. They are formed during a process called sporulation,
typically when nutrients become limited. Once favorable conditions return, the endospore
can germinate back into a vegetative cell.
5. Which transport system uses ATP to move solutes against a concentration gradient and is
common in both Bacteria and Archaea?
A. Group translocation
B. Simple diffusion
C. Facilitated diffusion
D. ABC transporters
Answer: D
Rationale: ATP-binding cassette (ABC) transporters are primary active transporters that
utilize ATP hydrolysis to move substrates across the membrane. These systems typically
consist of a periplasmic binding protein, a transmembrane channel, and an ATP-
hydrolyzing protein. They are highly specific and can transport nutrients even when they
are present at very low concentrations in the environment.
6. During which phase of the bacterial growth curve is the population growing at its
maximum rate?
A. Lag phase
B. Death phase
C. Stationary phase
D. Log (Exponential) phase
Answer: D
, Rationale: The log phase is characterized by cell doubling at a constant, maximum rate
given the environmental conditions. During this time, the metabolic activity is highest, and
the generation time is at its shortest. Researchers often use cells from this phase for
experiments because the population is most uniform.
7. Organisms that grow optimally at temperatures between 45°C and 80°C are classified as:
A. Psychrophiles
B. Mesophiles
C. Thermophiles
D. Hyperthermophiles
Answer: C
Rationale: Thermophiles are adapted to high-temperature environments, such as hot
springs or compost piles. Their proteins and membranes are specifically evolved to remain
stable and functional at temperatures that would denature most mesophilic organisms.
This stability is often due to increased ionic bonding and highly hydrophobic interiors of
their proteins.
8. Microorganisms that do not use oxygen for energy but are not harmed by its presence are
called:
A. Obligate aerobes
B. Microaerophiles
C. Obligate anaerobes
D. Aerotolerant anaerobes
Answer: D
Rationale: Aerotolerant anaerobes possess enzymes like superoxide dismutase or
peroxidase to neutralize toxic oxygen species. However, they rely exclusively on
fermentation or anaerobic respiration for energy production. This distinguishes them from
facultative anaerobes, which prefer using oxygen if it is available.
9. Which of the following describes a facultative anaerobe?
A. It grows only in the presence of oxygen.
B. It grows better with oxygen but can grow without it.
C. It is killed by the presence of oxygen.
D. It requires a specific low concentration of oxygen.
Answer: B
