BIO 250 Exam 1 V1 | BIO 250 Microbiology
| Actual Q&A with Rationale (BIO250 Exam
1) | StraighterLine
1. Who was the first individual to observe ‘animalcules’ under a microscope?
A. Louis Pasteur
B. Robert Hooke
C. Antonie van Leeuwenhoek
D. Robert Koch
Answer: C
Rationale: Antonie van Leeuwenhoek is credited with the first observations of bacteria
and protozoa using high-quality single lenses he crafted. He referred to these moving
organisms as ‘animalcules’ in his reports to the Royal Society. His work laid the foundation
for the field of microbiology by proving the existence of microscopic life.
2. Which of the following is the correct order of the taxonomic hierarchy from most general
to most specific?
A. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
B. Kingdom, Phylum, Domain, Class, Family, Order, Genus, Species
C. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
D. Phylum, Domain, Kingdom, Class, Order, Family, Genus, Species
,Answer: C
Rationale: The taxonomic hierarchy begins with the broadest category, the Domain, and
ends with the most specific, the Species. This system organizes life into nested groups
based on shared evolutionary characteristics and genetic relationships. Understanding this
hierarchy is essential for classifying and identifying microorganisms in clinical and
environmental settings.
3. Which of the following structures are found in all prokaryotic cells? (Select All That Apply)
A. Cytoplasm
B. Ribosomes
C. Mitochondria
D. Cell Membrane
E. Nuclear Envelope
F. Nucleoid region
Answer: A, B, D, F
Rationale: All prokaryotic cells lack a membrane-bound nucleus but contain a nucleoid
region where DNA is concentrated. They also possess a cell membrane and cytoplasm to
maintain internal functions and ribosomes for protein synthesis. Mitochondria and nuclear
envelopes are distinct features of eukaryotic cells and are never found in prokaryotes.
, 4. What is the primary function of the bacterial cell wall?
A. Energy production
B. Protein synthesis
C. To prevent osmotic lysis
D. Selective permeability
Answer: C
Rationale: The bacterial cell wall is a rigid structure composed primarily of peptidoglycan
that protects the cell from internal pressure. It prevents the cell from bursting, or
undergoing osmotic lysis, when placed in a hypotonic environment. This structural
integrity is vital for survival across varying environmental conditions.
5. In the Gram stain procedure, what is the role of Iodine?
A. Mordant
B. Primary stain
C. Decolorizer
D. Counterstain
Answer: A
Rationale: Iodine acts as a mordant by forming a complex with the crystal violet dye inside
the cell wall. This CV-I complex is larger than the individual molecules and becomes
| Actual Q&A with Rationale (BIO250 Exam
1) | StraighterLine
1. Who was the first individual to observe ‘animalcules’ under a microscope?
A. Louis Pasteur
B. Robert Hooke
C. Antonie van Leeuwenhoek
D. Robert Koch
Answer: C
Rationale: Antonie van Leeuwenhoek is credited with the first observations of bacteria
and protozoa using high-quality single lenses he crafted. He referred to these moving
organisms as ‘animalcules’ in his reports to the Royal Society. His work laid the foundation
for the field of microbiology by proving the existence of microscopic life.
2. Which of the following is the correct order of the taxonomic hierarchy from most general
to most specific?
A. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
B. Kingdom, Phylum, Domain, Class, Family, Order, Genus, Species
C. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
D. Phylum, Domain, Kingdom, Class, Order, Family, Genus, Species
,Answer: C
Rationale: The taxonomic hierarchy begins with the broadest category, the Domain, and
ends with the most specific, the Species. This system organizes life into nested groups
based on shared evolutionary characteristics and genetic relationships. Understanding this
hierarchy is essential for classifying and identifying microorganisms in clinical and
environmental settings.
3. Which of the following structures are found in all prokaryotic cells? (Select All That Apply)
A. Cytoplasm
B. Ribosomes
C. Mitochondria
D. Cell Membrane
E. Nuclear Envelope
F. Nucleoid region
Answer: A, B, D, F
Rationale: All prokaryotic cells lack a membrane-bound nucleus but contain a nucleoid
region where DNA is concentrated. They also possess a cell membrane and cytoplasm to
maintain internal functions and ribosomes for protein synthesis. Mitochondria and nuclear
envelopes are distinct features of eukaryotic cells and are never found in prokaryotes.
, 4. What is the primary function of the bacterial cell wall?
A. Energy production
B. Protein synthesis
C. To prevent osmotic lysis
D. Selective permeability
Answer: C
Rationale: The bacterial cell wall is a rigid structure composed primarily of peptidoglycan
that protects the cell from internal pressure. It prevents the cell from bursting, or
undergoing osmotic lysis, when placed in a hypotonic environment. This structural
integrity is vital for survival across varying environmental conditions.
5. In the Gram stain procedure, what is the role of Iodine?
A. Mordant
B. Primary stain
C. Decolorizer
D. Counterstain
Answer: A
Rationale: Iodine acts as a mordant by forming a complex with the crystal violet dye inside
the cell wall. This CV-I complex is larger than the individual molecules and becomes
