BIO 250 Exam 1 V3 | BIO 250 Microbiology | Actual
Q&A with Rationale (BIO250 Exam 1) |
StraighterLine
1. Louis Pasteur is best known in the field of microbiology for which of the following
contributions?
A. Developing the first compound microscope
B. Disproving the theory of spontaneous generation using swan-neck flasks
C. Discovering the first antibiotic, penicillin
D. Formulating the four postulates to link a specific microbe to a disease
Correct Answer: B
Explanation: Louis Pasteur used swan-neck flasks to demonstrate that microbes in the air
were responsible for contaminating broth, not a ‘vital force’ in the air itself. This
experiment effectively ended the debate over spontaneous generation and supported the
theory of biogenesis. His work laid the foundation for aseptic techniques used in modern
science and medicine.
2. Select all of the following structures that are found in all prokaryotic cells. (Select All That
Apply)
A. Ribosomes
B. Nucleus
,C. Cell membrane
D. Mitochondria
E. DNA (Chromosomes)
F. Cytoplasm
Correct Answer: A, C, E, F
Explanation: All prokaryotic cells possess ribosomes for protein synthesis, a cell
membrane to regulate transport, DNA to carry genetic information, and cytoplasm as a site
for metabolic reactions. Structures like the nucleus and mitochondria are membrane-
bound organelles exclusive to eukaryotic cells. Understanding these universal components
is essential for identifying bacterial life forms.
3. In the Gram staining procedure, what is the role of iodine?
A. Acting as the primary stain to color all cells purple
B. Acting as a mordant to form a complex with crystal violet
C. Serving as a decolorizer to remove the primary stain
D. Functioning as a counterstain to color Gram-negative cells pink
Correct Answer: B
Explanation: Iodine acts as a mordant that binds with the crystal violet dye inside the
thick peptidoglycan layer of Gram-positive cells. This large CV-I complex is trapped within
, the cell wall, making it resistant to decolorization. Without the mordant, the primary stain
would wash away easily from all cells, leading to incorrect results.
4. Which term describes a bacterial cell that has a single flagellum at one end?
A. Monotrichous
B. Lophotrichous
C. Peritrichous
D. Amphitrichous
Correct Answer: A
Explanation: Monotrichous refers to a single flagellum located at one pole of the cell. Other
arrangements include amphitrichous (flagella at both poles) and peritrichous (flagella
dispersed over the entire surface). These arrangements are critical for bacterial chemotaxis
and identification in the laboratory.
5. Robert Koch’s postulates are a series of criteria used to:
A. Differentiate between Gram-positive and Gram-negative bacteria
B. Identify the causative agent of a specific infectious disease
C. Calculate the magnification of a light microscope
D. Determine the optimal growth temperature for thermophiles
Correct Answer: B
Q&A with Rationale (BIO250 Exam 1) |
StraighterLine
1. Louis Pasteur is best known in the field of microbiology for which of the following
contributions?
A. Developing the first compound microscope
B. Disproving the theory of spontaneous generation using swan-neck flasks
C. Discovering the first antibiotic, penicillin
D. Formulating the four postulates to link a specific microbe to a disease
Correct Answer: B
Explanation: Louis Pasteur used swan-neck flasks to demonstrate that microbes in the air
were responsible for contaminating broth, not a ‘vital force’ in the air itself. This
experiment effectively ended the debate over spontaneous generation and supported the
theory of biogenesis. His work laid the foundation for aseptic techniques used in modern
science and medicine.
2. Select all of the following structures that are found in all prokaryotic cells. (Select All That
Apply)
A. Ribosomes
B. Nucleus
,C. Cell membrane
D. Mitochondria
E. DNA (Chromosomes)
F. Cytoplasm
Correct Answer: A, C, E, F
Explanation: All prokaryotic cells possess ribosomes for protein synthesis, a cell
membrane to regulate transport, DNA to carry genetic information, and cytoplasm as a site
for metabolic reactions. Structures like the nucleus and mitochondria are membrane-
bound organelles exclusive to eukaryotic cells. Understanding these universal components
is essential for identifying bacterial life forms.
3. In the Gram staining procedure, what is the role of iodine?
A. Acting as the primary stain to color all cells purple
B. Acting as a mordant to form a complex with crystal violet
C. Serving as a decolorizer to remove the primary stain
D. Functioning as a counterstain to color Gram-negative cells pink
Correct Answer: B
Explanation: Iodine acts as a mordant that binds with the crystal violet dye inside the
thick peptidoglycan layer of Gram-positive cells. This large CV-I complex is trapped within
, the cell wall, making it resistant to decolorization. Without the mordant, the primary stain
would wash away easily from all cells, leading to incorrect results.
4. Which term describes a bacterial cell that has a single flagellum at one end?
A. Monotrichous
B. Lophotrichous
C. Peritrichous
D. Amphitrichous
Correct Answer: A
Explanation: Monotrichous refers to a single flagellum located at one pole of the cell. Other
arrangements include amphitrichous (flagella at both poles) and peritrichous (flagella
dispersed over the entire surface). These arrangements are critical for bacterial chemotaxis
and identification in the laboratory.
5. Robert Koch’s postulates are a series of criteria used to:
A. Differentiate between Gram-positive and Gram-negative bacteria
B. Identify the causative agent of a specific infectious disease
C. Calculate the magnification of a light microscope
D. Determine the optimal growth temperature for thermophiles
Correct Answer: B
