BIO 250 Exam 1 V2 | BIO 250 Microbiology
| Actual Q&A with Rationale (BIO250 Exam
1) | StraighterLine
1. Which scientist is credited with definitively disproving the theory of spontaneous
generation using a swan-necked flask?
A. Louis Pasteur
B. Robert Koch
C. Antonie van Leeuwenhoek
D. Joseph Lister
Answer: A
Rationale: Louis Pasteur designed a flask with a long, curved neck that allowed air in but
trapped dust and microbes. His experiments showed that broth remained sterile unless the
flask was tilted to contact the trapped particles. This work provided critical evidence
against the idea that life could arise from non-living matter.
2. In the binomial system of nomenclature, which of the following is the correct way to
represent the scientific name of a common bacterium?
A. Escherichia Coli
B. escherichia Coli
C. Escherichia coli
,D. escherichia coli
Answer: C
Rationale: The binomial system requires the Genus name to be capitalized and the species
epithet to be lowercase. Both names must be italicized when typed or underlined when
handwritten. This standardized system ensures clear communication among scientists
globally regarding specific organisms.
3. Which of the following structures is found in both eukaryotic and prokaryotic cells?
A. Ribosomes
B. Nucleus
C. Mitochondria
D. Lysosomes
Answer: A
Rationale: Ribosomes are essential for protein synthesis and are present in all living cells
regardless of their complexity. While prokaryotic ribosomes are 70S and eukaryotic
ribosomes are 80S, their fundamental function remains the same. Membrane-bound
organelles like mitochondria and nuclei are exclusively found in eukaryotes.
4. Which type of microscopy uses a UV light source to visualize specimens that have been
stained with specific dyes?
A. Phase-contrast microscopy
, B. Fluorescence microscopy
C. Bright-field microscopy
D. Dark-field microscopy
Answer: B
Rationale: Fluorescence microscopy utilizes ultraviolet light to excite fluorochromes
within a specimen. These molecules then emit light of a longer wavelength, which is visible
through the ocular lens. This technique is particularly useful for identifying specific
pathogens using fluorescently labeled antibodies.
5. Identify the characteristics associated with Gram-negative bacterial cell walls. (Select all
that apply)
A. Thick layer of peptidoglycan
B. Outer membrane containing lipopolysaccharide (LPS)
C. Periplasmic space
D. Teichoic acids
E. Porin proteins
F. Thin layer of peptidoglycan
Answer: B, C, E, F
Rationale: Gram-negative bacteria are characterized by a complex cell envelope including
an outer membrane and a thin peptidoglycan layer. The outer membrane contains
| Actual Q&A with Rationale (BIO250 Exam
1) | StraighterLine
1. Which scientist is credited with definitively disproving the theory of spontaneous
generation using a swan-necked flask?
A. Louis Pasteur
B. Robert Koch
C. Antonie van Leeuwenhoek
D. Joseph Lister
Answer: A
Rationale: Louis Pasteur designed a flask with a long, curved neck that allowed air in but
trapped dust and microbes. His experiments showed that broth remained sterile unless the
flask was tilted to contact the trapped particles. This work provided critical evidence
against the idea that life could arise from non-living matter.
2. In the binomial system of nomenclature, which of the following is the correct way to
represent the scientific name of a common bacterium?
A. Escherichia Coli
B. escherichia Coli
C. Escherichia coli
,D. escherichia coli
Answer: C
Rationale: The binomial system requires the Genus name to be capitalized and the species
epithet to be lowercase. Both names must be italicized when typed or underlined when
handwritten. This standardized system ensures clear communication among scientists
globally regarding specific organisms.
3. Which of the following structures is found in both eukaryotic and prokaryotic cells?
A. Ribosomes
B. Nucleus
C. Mitochondria
D. Lysosomes
Answer: A
Rationale: Ribosomes are essential for protein synthesis and are present in all living cells
regardless of their complexity. While prokaryotic ribosomes are 70S and eukaryotic
ribosomes are 80S, their fundamental function remains the same. Membrane-bound
organelles like mitochondria and nuclei are exclusively found in eukaryotes.
4. Which type of microscopy uses a UV light source to visualize specimens that have been
stained with specific dyes?
A. Phase-contrast microscopy
, B. Fluorescence microscopy
C. Bright-field microscopy
D. Dark-field microscopy
Answer: B
Rationale: Fluorescence microscopy utilizes ultraviolet light to excite fluorochromes
within a specimen. These molecules then emit light of a longer wavelength, which is visible
through the ocular lens. This technique is particularly useful for identifying specific
pathogens using fluorescently labeled antibodies.
5. Identify the characteristics associated with Gram-negative bacterial cell walls. (Select all
that apply)
A. Thick layer of peptidoglycan
B. Outer membrane containing lipopolysaccharide (LPS)
C. Periplasmic space
D. Teichoic acids
E. Porin proteins
F. Thin layer of peptidoglycan
Answer: B, C, E, F
Rationale: Gram-negative bacteria are characterized by a complex cell envelope including
an outer membrane and a thin peptidoglycan layer. The outer membrane contains
