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BIOD 171 MIDTERM EXAM 2026/2027 | MICROBIOLOGY
& ANATOMY | PORTAGE LEARNING | 100 VERIFIED
Q&A | DETAILED RATIONALES | PASS GUARANTEED
Total Questions: 100
Time Allowed: 2 Hours
Format: Multiple Choice, Select All That Apply, Matching, Fill-in-the-Blank, Short Answer
Evidence-Based Guidelines: 2026/2027
SECTION A: MULTIPLE CHOICE (Questions 1-60)
Instructions: Select the single best answer for each question.
1. Which of the following is the primary difference between prokaryotic and eukaryotic cells?
• A) Presence of ribosomes
• B) Presence of a cell membrane
• C) Presence of a nucleus
• D) Presence of cytoplasm
Answer: C) Presence of a nucleus
Rationale: Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells contain a true
nucleus that houses their genetic material. Both cell types contain ribosomes (though different
sizes), cell membranes, and cytoplasm. This fundamental distinction forms the basis of the
prokaryotic/eukaryotic classification system in microbiology.
Teaching Point: Prokaryotes (bacteria and archaea) have DNA concentrated in the nucleoid region
without a nuclear membrane. Eukaryotes (fungi, protozoa, plants, animals) have a defined nucleus
with a nuclear envelope.
2. Which bacterial structure is responsible for attachment to surfaces and contributes to biofilm
formation?
• A) Flagella
• B) Pili (Fimbriae)
• C) Capsule
• D) Cell wall
Answer: B) Pili (Fimbriae)
,2
Rationale: Pili (or fimbriae) are hair-like protein appendages on the bacterial surface that facilitate
attachment to host cells and surfaces. They are critical for biofilm formation and colonization. While
flagella provide motility, capsules offer protection from phagocytosis, and cell walls maintain
structural integrity.
Teaching Point: There are two types of pili: (1) common pili/fimbriae for attachment, and (2) sex pili
(F-pili) for conjugation (transfer of genetic material).
3. A gram-positive bacterium appears what color after the Gram staining procedure?
• A) Pink
• B) Purple
• C) Colorless
• D) Green
Answer: B) Purple
Rationale: Gram-positive bacteria retain the crystal violet-iodine complex due to their thick
peptidoglycan layer and appear purple after Gram staining. Gram-negative bacteria have a thinner
peptidoglycan layer and an outer membrane, causing them to lose the crystal violet and take up the
counterstain (safranin), appearing pink/red.
Teaching Point: The Gram stain is the most important differential stain in bacteriology. Key
differences:
• Gram-positive: Thick peptidoglycan (90%), teichoic acids, no outer membrane
• Gram-negative: Thin peptidoglycan (10%), outer membrane with lipopolysaccharide (LPS)
4. Which of the following is NOT a characteristic of viruses?
• A) Can reproduce independently
• B) Contain DNA or RNA (not both)
• C) Obligate intracellular parasites
• D) Lack cellular organelles
Answer: A) Can reproduce independently
Rationale: Viruses are obligate intracellular parasites that cannot reproduce independently. They
require host cellular machinery to replicate. Viruses contain either DNA or RNA (never both), lack
cellular structures (organelles, ribosomes, cell membrane), and cannot carry out metabolic
processes on their own.
Teaching Point: Viruses exist in two states:
• Extracellular (virion): Inert, non-replicating particle
• Intracellular: Active, replicating using host cell machinery
,3
5. The most common type of microscope used to observe live microorganisms is:
• A) Electron microscope
• B) Phase-contrast microscope
• C) Scanning electron microscope
• D) Fluorescence microscope
Answer: B) Phase-contrast microscope
Rationale: Phase-contrast microscopy allows observation of live, unstained microorganisms by
enhancing contrast between cells and their surrounding medium. This is achieved by exploiting
differences in refractive index. Electron microscopes require specimens to be fixed and dehydrated
(killing the organism), and fluorescence microscopy requires staining.
Teaching Point: Different types of microscopy and their uses:
• Bright-field: Standard, stained specimens
• Phase-contrast: Live, unstained organisms
• Dark-field: Live, unstained, highly reflective specimens
• Fluorescence: Fluorescently stained specimens
• Electron: Ultra-high magnification of fixed specimens
6. Which of the following is the correct order of taxonomic classification from broadest to most
specific?
• A) Kingdom, Phylum, Class, Order, Family, Genus, Species
• B) Kingdom, Class, Phylum, Order, Family, Genus, Species
• C) Phylum, Kingdom, Class, Order, Family, Genus, Species
• D) Kingdom, Phylum, Order, Class, Family, Genus, Species
Answer: A) Kingdom, Phylum, Class, Order, Family, Genus, Species
Rationale: The taxonomic hierarchy from broadest to most specific is: Kingdom, Phylum, Class,
Order, Family, Genus, Species. A common mnemonic is "King Philip Came Over For Good Soup."
Teaching Point: Modern taxonomy also includes Domains (Archaea, Bacteria, Eukarya) above the
Kingdom level, based on molecular evidence (rRNA sequencing).
7. The bacterial cell wall is composed primarily of:
• A) Cellulose
• B) Chitin
, 4
• C) Peptidoglycan
• D) Lipopolysaccharide
Answer: C) Peptidoglycan
Rationale: Peptidoglycan (also called murein) is the primary component of bacterial cell walls. It
consists of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by
peptide chains. This unique structure provides structural support and protection.
Teaching Point: Peptidoglycan is found only in bacteria, making it an excellent target for antibiotics
(e.g., penicillin inhibits peptidoglycan synthesis). Archaea have pseudomurein or other cell wall
components.
8. Which of the following is a characteristic of archaea?
• A) Have peptidoglycan in cell walls
• B) Are always pathogenic
• C) Have membrane lipids with ether linkages
• D) Contain a nucleus
Answer: C) Have membrane lipids with ether linkages
Rationale: Archaea are distinguished by their unique membrane lipids that contain ether linkages
(rather than ester linkages found in bacteria and eukaryotes). This adaptation allows them to survive
in extreme environments. They do NOT have peptidoglycan in their cell walls and are generally not
pathogenic.
Teaching Point: Archaea are known as extremophiles and thrive in environments such as hot
springs, highly saline waters, and anaerobic conditions. They are evolutionarily distinct from
bacteria.
9. The function of the bacterial capsule is primarily to:
• A) Provide motility
• B) Protect against phagocytosis
• C) Transfer genetic material
• D) Produce energy
Answer: B) Protect against phagocytosis
Rationale: The capsule is a gelatinous outer layer composed of polysaccharides that protects
bacteria from phagocytosis by white blood cells. It also helps bacteria adhere to surfaces and
protects against desiccation. Flagella provide motility, pili transfer genetic material, and the cell
membrane produces energy.
BIOD 171 MIDTERM EXAM 2026/2027 | MICROBIOLOGY
& ANATOMY | PORTAGE LEARNING | 100 VERIFIED
Q&A | DETAILED RATIONALES | PASS GUARANTEED
Total Questions: 100
Time Allowed: 2 Hours
Format: Multiple Choice, Select All That Apply, Matching, Fill-in-the-Blank, Short Answer
Evidence-Based Guidelines: 2026/2027
SECTION A: MULTIPLE CHOICE (Questions 1-60)
Instructions: Select the single best answer for each question.
1. Which of the following is the primary difference between prokaryotic and eukaryotic cells?
• A) Presence of ribosomes
• B) Presence of a cell membrane
• C) Presence of a nucleus
• D) Presence of cytoplasm
Answer: C) Presence of a nucleus
Rationale: Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells contain a true
nucleus that houses their genetic material. Both cell types contain ribosomes (though different
sizes), cell membranes, and cytoplasm. This fundamental distinction forms the basis of the
prokaryotic/eukaryotic classification system in microbiology.
Teaching Point: Prokaryotes (bacteria and archaea) have DNA concentrated in the nucleoid region
without a nuclear membrane. Eukaryotes (fungi, protozoa, plants, animals) have a defined nucleus
with a nuclear envelope.
2. Which bacterial structure is responsible for attachment to surfaces and contributes to biofilm
formation?
• A) Flagella
• B) Pili (Fimbriae)
• C) Capsule
• D) Cell wall
Answer: B) Pili (Fimbriae)
,2
Rationale: Pili (or fimbriae) are hair-like protein appendages on the bacterial surface that facilitate
attachment to host cells and surfaces. They are critical for biofilm formation and colonization. While
flagella provide motility, capsules offer protection from phagocytosis, and cell walls maintain
structural integrity.
Teaching Point: There are two types of pili: (1) common pili/fimbriae for attachment, and (2) sex pili
(F-pili) for conjugation (transfer of genetic material).
3. A gram-positive bacterium appears what color after the Gram staining procedure?
• A) Pink
• B) Purple
• C) Colorless
• D) Green
Answer: B) Purple
Rationale: Gram-positive bacteria retain the crystal violet-iodine complex due to their thick
peptidoglycan layer and appear purple after Gram staining. Gram-negative bacteria have a thinner
peptidoglycan layer and an outer membrane, causing them to lose the crystal violet and take up the
counterstain (safranin), appearing pink/red.
Teaching Point: The Gram stain is the most important differential stain in bacteriology. Key
differences:
• Gram-positive: Thick peptidoglycan (90%), teichoic acids, no outer membrane
• Gram-negative: Thin peptidoglycan (10%), outer membrane with lipopolysaccharide (LPS)
4. Which of the following is NOT a characteristic of viruses?
• A) Can reproduce independently
• B) Contain DNA or RNA (not both)
• C) Obligate intracellular parasites
• D) Lack cellular organelles
Answer: A) Can reproduce independently
Rationale: Viruses are obligate intracellular parasites that cannot reproduce independently. They
require host cellular machinery to replicate. Viruses contain either DNA or RNA (never both), lack
cellular structures (organelles, ribosomes, cell membrane), and cannot carry out metabolic
processes on their own.
Teaching Point: Viruses exist in two states:
• Extracellular (virion): Inert, non-replicating particle
• Intracellular: Active, replicating using host cell machinery
,3
5. The most common type of microscope used to observe live microorganisms is:
• A) Electron microscope
• B) Phase-contrast microscope
• C) Scanning electron microscope
• D) Fluorescence microscope
Answer: B) Phase-contrast microscope
Rationale: Phase-contrast microscopy allows observation of live, unstained microorganisms by
enhancing contrast between cells and their surrounding medium. This is achieved by exploiting
differences in refractive index. Electron microscopes require specimens to be fixed and dehydrated
(killing the organism), and fluorescence microscopy requires staining.
Teaching Point: Different types of microscopy and their uses:
• Bright-field: Standard, stained specimens
• Phase-contrast: Live, unstained organisms
• Dark-field: Live, unstained, highly reflective specimens
• Fluorescence: Fluorescently stained specimens
• Electron: Ultra-high magnification of fixed specimens
6. Which of the following is the correct order of taxonomic classification from broadest to most
specific?
• A) Kingdom, Phylum, Class, Order, Family, Genus, Species
• B) Kingdom, Class, Phylum, Order, Family, Genus, Species
• C) Phylum, Kingdom, Class, Order, Family, Genus, Species
• D) Kingdom, Phylum, Order, Class, Family, Genus, Species
Answer: A) Kingdom, Phylum, Class, Order, Family, Genus, Species
Rationale: The taxonomic hierarchy from broadest to most specific is: Kingdom, Phylum, Class,
Order, Family, Genus, Species. A common mnemonic is "King Philip Came Over For Good Soup."
Teaching Point: Modern taxonomy also includes Domains (Archaea, Bacteria, Eukarya) above the
Kingdom level, based on molecular evidence (rRNA sequencing).
7. The bacterial cell wall is composed primarily of:
• A) Cellulose
• B) Chitin
, 4
• C) Peptidoglycan
• D) Lipopolysaccharide
Answer: C) Peptidoglycan
Rationale: Peptidoglycan (also called murein) is the primary component of bacterial cell walls. It
consists of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by
peptide chains. This unique structure provides structural support and protection.
Teaching Point: Peptidoglycan is found only in bacteria, making it an excellent target for antibiotics
(e.g., penicillin inhibits peptidoglycan synthesis). Archaea have pseudomurein or other cell wall
components.
8. Which of the following is a characteristic of archaea?
• A) Have peptidoglycan in cell walls
• B) Are always pathogenic
• C) Have membrane lipids with ether linkages
• D) Contain a nucleus
Answer: C) Have membrane lipids with ether linkages
Rationale: Archaea are distinguished by their unique membrane lipids that contain ether linkages
(rather than ester linkages found in bacteria and eukaryotes). This adaptation allows them to survive
in extreme environments. They do NOT have peptidoglycan in their cell walls and are generally not
pathogenic.
Teaching Point: Archaea are known as extremophiles and thrive in environments such as hot
springs, highly saline waters, and anaerobic conditions. They are evolutionarily distinct from
bacteria.
9. The function of the bacterial capsule is primarily to:
• A) Provide motility
• B) Protect against phagocytosis
• C) Transfer genetic material
• D) Produce energy
Answer: B) Protect against phagocytosis
Rationale: The capsule is a gelatinous outer layer composed of polysaccharides that protects
bacteria from phagocytosis by white blood cells. It also helps bacteria adhere to surfaces and
protects against desiccation. Flagella provide motility, pili transfer genetic material, and the cell
membrane produces energy.
