BIO 250 Final Exam V3 | BIO 250 Microbiology |
Actual Q&A with Rationale (BIO250 Final Exam) |
StraighterLine
1. Which of the following structures are found in all prokaryotic cells? Select all that apply.
A. Cell membrane
B. Cytoplasm
C. Nucleus
D. Ribosomes
E. Mitochondria
F. DNA/Genome
Correct Answer: A, B, D, F
Explanation: All prokaryotic cells possess a cell membrane, cytoplasm, ribosomes for
protein synthesis, and genetic material in the form of DNA. They lack membrane-bound
organelles such as the nucleus and mitochondria, which are characteristic of eukaryotic
cells. The presence of these four components is fundamental to the survival and function of
any bacterial cell.
2. In the Gram staining procedure, what is the specific role of the iodine solution?
A. It acts as the primary stain to color all cells purple.
B. It acts as a mordant to form a complex with crystal violet.
,C. It decolorizes the Gram-negative cells by dissolving lipids.
D. It serves as a counterstain to provide contrast for pink cells.
Correct Answer: B
Explanation: Iodine is applied after the primary stain, crystal violet, to serve as a mordant.
It forms a large CV-I complex that becomes trapped within the thick peptidoglycan layer of
Gram-positive bacteria. This step is crucial because it prevents the primary stain from
being easily washed out during the decolorization process.
3. A strictly fermentative bacterium produces energy by which of the following processes?
A. Glycolysis followed by the reduction of pyruvate.
B. Anaerobic respiration using nitrate as an electron acceptor
C. Aerobic respiration only
D. The Krebs cycle and electron transport chain
E. Photophosphorylation
Correct Answer: A
Explanation: Fermentation relies solely on glycolysis to produce a small amount of ATP
through substrate-level phosphorylation. Since these organisms lack an electron transport
chain, they must reduce pyruvate or its derivatives to regenerate NAD+ from NADH. This
regeneration allows the glycolytic pathway to continue functioning in the absence of
external electron acceptors.
, 4. Which of the following best describes the function of bacterial endospores?
A. They are dormant structures that allow survival in harsh conditions.
B. They facilitate the exchange of genetic material via conjugation.
C. They are a method of rapid reproductive multiplication.
D. They are primary structures used for motility in liquid media.
Correct Answer: A
Explanation: Endospores are highly resistant, non-reproductive structures produced by
certain bacteria like Bacillus and Clostridium. They are designed to protect the bacterial
genome from extreme heat, radiation, and chemical disinfectants. When environmental
conditions improve, the endospore can germinate back into a vegetative cell.
5. During which phase of the bacterial growth curve are bacteria most sensitive to antibiotics
like penicillin?
A. Lag phase
B. Log (Exponential) phase
C. Stationary phase
D. Death (Decline) phase
Correct Answer: B
Explanation: The log phase is characterized by rapid cell division and active peptidoglycan
synthesis. Penicillin inhibits the transpeptidase enzyme responsible for cross-linking the
Actual Q&A with Rationale (BIO250 Final Exam) |
StraighterLine
1. Which of the following structures are found in all prokaryotic cells? Select all that apply.
A. Cell membrane
B. Cytoplasm
C. Nucleus
D. Ribosomes
E. Mitochondria
F. DNA/Genome
Correct Answer: A, B, D, F
Explanation: All prokaryotic cells possess a cell membrane, cytoplasm, ribosomes for
protein synthesis, and genetic material in the form of DNA. They lack membrane-bound
organelles such as the nucleus and mitochondria, which are characteristic of eukaryotic
cells. The presence of these four components is fundamental to the survival and function of
any bacterial cell.
2. In the Gram staining procedure, what is the specific role of the iodine solution?
A. It acts as the primary stain to color all cells purple.
B. It acts as a mordant to form a complex with crystal violet.
,C. It decolorizes the Gram-negative cells by dissolving lipids.
D. It serves as a counterstain to provide contrast for pink cells.
Correct Answer: B
Explanation: Iodine is applied after the primary stain, crystal violet, to serve as a mordant.
It forms a large CV-I complex that becomes trapped within the thick peptidoglycan layer of
Gram-positive bacteria. This step is crucial because it prevents the primary stain from
being easily washed out during the decolorization process.
3. A strictly fermentative bacterium produces energy by which of the following processes?
A. Glycolysis followed by the reduction of pyruvate.
B. Anaerobic respiration using nitrate as an electron acceptor
C. Aerobic respiration only
D. The Krebs cycle and electron transport chain
E. Photophosphorylation
Correct Answer: A
Explanation: Fermentation relies solely on glycolysis to produce a small amount of ATP
through substrate-level phosphorylation. Since these organisms lack an electron transport
chain, they must reduce pyruvate or its derivatives to regenerate NAD+ from NADH. This
regeneration allows the glycolytic pathway to continue functioning in the absence of
external electron acceptors.
, 4. Which of the following best describes the function of bacterial endospores?
A. They are dormant structures that allow survival in harsh conditions.
B. They facilitate the exchange of genetic material via conjugation.
C. They are a method of rapid reproductive multiplication.
D. They are primary structures used for motility in liquid media.
Correct Answer: A
Explanation: Endospores are highly resistant, non-reproductive structures produced by
certain bacteria like Bacillus and Clostridium. They are designed to protect the bacterial
genome from extreme heat, radiation, and chemical disinfectants. When environmental
conditions improve, the endospore can germinate back into a vegetative cell.
5. During which phase of the bacterial growth curve are bacteria most sensitive to antibiotics
like penicillin?
A. Lag phase
B. Log (Exponential) phase
C. Stationary phase
D. Death (Decline) phase
Correct Answer: B
Explanation: The log phase is characterized by rapid cell division and active peptidoglycan
synthesis. Penicillin inhibits the transpeptidase enzyme responsible for cross-linking the
