BIO 101 BACTERIAL CELL STRUCTURES
LAB MASTER 2026 150 PRACTICAL Q&AS
+ EXPERT RATIONALES
Part I: Microscopy, Morphology, & Surface
Appendages (1–25)
1. An undergraduate student is observing a slide of Bacillus
anthracis under the oil immersion lens (100x objective) of
a compound light microscope. Which of the following
spatial descriptions best characterizes the arrangement of
this bacterial cell morphology?
A. Spherical clusters resembling grapes
B. Spiral-shaped rigid cylinders
Correct Answer: C. Rod-shaped cells arranged
in linear chains
D. Comma-shaped single curved cells
Rationale: Bacillus cells are structurally rod-shaped.
When they form strings or chains, they are described
morphologically as streptobacilli.
2. During an experiment, a student treats a culture of
Escherichia coli with a chemical that selectively hydrolyzes
the protein pilin. Which of the following cellular
processes will be immediately compromised in these
bacteria?
A. Adenosine triphosphate (ATP) synthesis via oxidative
phosphorylation
Correct Answer: B. Adherence to host mucosal
surfaces and bacterial conjugation
C. Peptidoglycan cross-linking during binary fission
, D. Active transport of glucose across the plasma
membrane
Rationale: Pili are short, hair-like surface appendages
composed of the protein pilin. Specialized variations, like
sex pili, are essential for physical attachment to surfaces
and the horizontal transfer of genetic material via
conjugation.
3. Below is a foundational reference diagram of a typical
prokaryotic specimen. Use this structural model to assist
in visualizing internal and external structural boundaries
throughout this lab section:
Which architectural layer directly controls the passive and
active movement of solute molecules into and out of the
metabolic cytoplasm?
A. The outer polysaccharide capsule
B. The rigid peptidoglycan cell wall
Correct Answer: C. The semi-permeable
phospholipid plasma membrane
D. The crystalline surface S-layer proteins
Rationale: The plasma membrane is a semi-permeable
phospholipid bilayer embedded with transport proteins. It acts
as the primary selectively permeable barrier regulating
cellular influx and efflux.
4. A bacterial specimen isolates a localized population of
flagella clustered exclusively at one single pole of its rod-
shaped cell wall. What is the correct microbiological term
used to classify this flagellar arrangement?
Correct Answer: A. Monotrichous
B. Amphitrichous
C. Lophotrichous
D. Peritrichous
Rationale: Flagellar arrangements are categorized by
, distribution: monotrichous indicates a single flagellum at
one pole, lophotrichous describes a cluster at one or both
ends, amphitrichous means single flagella at both poles,
and peritrichous distributes flagella across the entire
surface.
5. While reviewing a slide of Micrococcus luteus, a student
notes perfectly spherical cells organized symmetrically
into cubical packings of eight cells. What is the precise
morphological classification for this arrangement?
A. Streptococcus
B. Staphylococcus
Correct Answer: C. Sarcina
D. Tetrad
Rationale: Cocci dividing across three perpendicular
planes produce regular, cubical packets of eight cells
structurally classified as Sarcina.
6. A research lab isolates a mutant strain of Salmonella
enterica that completely lacks a functional basal body
hook assembly. What primary physiological impairment
will this mutant display during phenotypic screening?
A. Inability to synthesize functional 70S ribosomes
B. Failure to absorb crystal violet dye during Gram
staining
Correct Answer: C. Complete loss of swimming
motility and chemotaxis
D. Inability to survive inside hypotonic liquid
environments
Rationale: The flagellum is a specialized rotatory
appendage used for movement. Its basal body acts as a
molecular motor embedded in the cell envelope; without
it, the flagellum cannot rotate to propel the cell.
7. A laboratory instructor describes an extracellular layer
composed of an unorganized, loosely attached meshwork
, of water-soluble polysaccharides that protects a bacterium
from dehydration. What structure is being described?
A. The outer membrane lipopolysaccharide layer
B. The rigid crystalline peptidoglycan matrix
Correct Answer: C. A slime layer
D. A true organized capsule
Rationale: Glycocalyx layers are classified by
structure: an organized, tightly bound layer is a capsule,
whereas an unorganized, loosely associated layer that
prevents desiccation is a slime layer.
8. During negative staining with nigrosin dye, a clear, halos-
like unstained region is observed surrounding cells of
Streptococcus pneumoniae. What is the chemical
composition and primary function of this protective
structural component?
Correct Answer: A. Polysaccharides;
preventing phagocytosis by host immune cells
B. Peptidoglycan; maintaining intracellular osmotic
pressure zones
C. Lipids; facilitating the active transport of hydrophobic
molecules
D. Proteins; serving as a docking site for bacteriophage
attachments
Rationale: Capsules are thick, organized
polysaccharide layers surrounding the cell wall. Because
they repel acidic dyes like nigrosin, they appear as clear
halos, physically masking the bacterium from phagocytic
white blood cells.
9. Which specific structural component of the bacterial
flagellum acts as the flexible joint connection that bridges
the embedded rotor motor to the long extracellular
filament blade?
A. The central MS ring
LAB MASTER 2026 150 PRACTICAL Q&AS
+ EXPERT RATIONALES
Part I: Microscopy, Morphology, & Surface
Appendages (1–25)
1. An undergraduate student is observing a slide of Bacillus
anthracis under the oil immersion lens (100x objective) of
a compound light microscope. Which of the following
spatial descriptions best characterizes the arrangement of
this bacterial cell morphology?
A. Spherical clusters resembling grapes
B. Spiral-shaped rigid cylinders
Correct Answer: C. Rod-shaped cells arranged
in linear chains
D. Comma-shaped single curved cells
Rationale: Bacillus cells are structurally rod-shaped.
When they form strings or chains, they are described
morphologically as streptobacilli.
2. During an experiment, a student treats a culture of
Escherichia coli with a chemical that selectively hydrolyzes
the protein pilin. Which of the following cellular
processes will be immediately compromised in these
bacteria?
A. Adenosine triphosphate (ATP) synthesis via oxidative
phosphorylation
Correct Answer: B. Adherence to host mucosal
surfaces and bacterial conjugation
C. Peptidoglycan cross-linking during binary fission
, D. Active transport of glucose across the plasma
membrane
Rationale: Pili are short, hair-like surface appendages
composed of the protein pilin. Specialized variations, like
sex pili, are essential for physical attachment to surfaces
and the horizontal transfer of genetic material via
conjugation.
3. Below is a foundational reference diagram of a typical
prokaryotic specimen. Use this structural model to assist
in visualizing internal and external structural boundaries
throughout this lab section:
Which architectural layer directly controls the passive and
active movement of solute molecules into and out of the
metabolic cytoplasm?
A. The outer polysaccharide capsule
B. The rigid peptidoglycan cell wall
Correct Answer: C. The semi-permeable
phospholipid plasma membrane
D. The crystalline surface S-layer proteins
Rationale: The plasma membrane is a semi-permeable
phospholipid bilayer embedded with transport proteins. It acts
as the primary selectively permeable barrier regulating
cellular influx and efflux.
4. A bacterial specimen isolates a localized population of
flagella clustered exclusively at one single pole of its rod-
shaped cell wall. What is the correct microbiological term
used to classify this flagellar arrangement?
Correct Answer: A. Monotrichous
B. Amphitrichous
C. Lophotrichous
D. Peritrichous
Rationale: Flagellar arrangements are categorized by
, distribution: monotrichous indicates a single flagellum at
one pole, lophotrichous describes a cluster at one or both
ends, amphitrichous means single flagella at both poles,
and peritrichous distributes flagella across the entire
surface.
5. While reviewing a slide of Micrococcus luteus, a student
notes perfectly spherical cells organized symmetrically
into cubical packings of eight cells. What is the precise
morphological classification for this arrangement?
A. Streptococcus
B. Staphylococcus
Correct Answer: C. Sarcina
D. Tetrad
Rationale: Cocci dividing across three perpendicular
planes produce regular, cubical packets of eight cells
structurally classified as Sarcina.
6. A research lab isolates a mutant strain of Salmonella
enterica that completely lacks a functional basal body
hook assembly. What primary physiological impairment
will this mutant display during phenotypic screening?
A. Inability to synthesize functional 70S ribosomes
B. Failure to absorb crystal violet dye during Gram
staining
Correct Answer: C. Complete loss of swimming
motility and chemotaxis
D. Inability to survive inside hypotonic liquid
environments
Rationale: The flagellum is a specialized rotatory
appendage used for movement. Its basal body acts as a
molecular motor embedded in the cell envelope; without
it, the flagellum cannot rotate to propel the cell.
7. A laboratory instructor describes an extracellular layer
composed of an unorganized, loosely attached meshwork
, of water-soluble polysaccharides that protects a bacterium
from dehydration. What structure is being described?
A. The outer membrane lipopolysaccharide layer
B. The rigid crystalline peptidoglycan matrix
Correct Answer: C. A slime layer
D. A true organized capsule
Rationale: Glycocalyx layers are classified by
structure: an organized, tightly bound layer is a capsule,
whereas an unorganized, loosely associated layer that
prevents desiccation is a slime layer.
8. During negative staining with nigrosin dye, a clear, halos-
like unstained region is observed surrounding cells of
Streptococcus pneumoniae. What is the chemical
composition and primary function of this protective
structural component?
Correct Answer: A. Polysaccharides;
preventing phagocytosis by host immune cells
B. Peptidoglycan; maintaining intracellular osmotic
pressure zones
C. Lipids; facilitating the active transport of hydrophobic
molecules
D. Proteins; serving as a docking site for bacteriophage
attachments
Rationale: Capsules are thick, organized
polysaccharide layers surrounding the cell wall. Because
they repel acidic dyes like nigrosin, they appear as clear
halos, physically masking the bacterium from phagocytic
white blood cells.
9. Which specific structural component of the bacterial
flagellum acts as the flexible joint connection that bridges
the embedded rotor motor to the long extracellular
filament blade?
A. The central MS ring
