BIOD 171 ESSENTIAL MICROBIOLOGY
COMPREHENSIVE EXAM BANK QUESTIONS &
ANSWERS | ALL MODULES 1-8 | 2026 EDITION
SECTION 1: CELL STRUCTURE & MICROBIAL
CLASSIFICATION
Questions 1-25
1. Which of the following is considered a "microbe" but is NOT classified as a
"microorganism"?
A. Bacteria
B. Archaea
C. Viruses
D. Fungi
Correct Answer: C
Rationale: Viruses lack cellular structure and cannot replicate outside of a host cell,
making them non-living. They are considered microbes but not microorganisms,
which must be living organisms .
2. Which of the following is the smallest biological unit of life?
A. Atom
B. Molecule
C. Cell
D. Tissue
,Correct Answer: C
Rationale: While atoms and molecules are smaller, the cell is the smallest unit that
can carry out all life processes independently, including metabolism and
reproduction .
3. Prokaryotic cells are characterized by the absence of:
A. A plasma membrane
B. DNA
C. A nucleus
D. Ribosomes
Correct Answer: C
Rationale: Prokaryotic cells lack a membrane-bound nucleus; their genetic material
is located in the nucleoid region. They do contain DNA, ribosomes, and a plasma
membrane .
4. Eukaryotic cells contain which of the following structures that prokaryotic
cells lack?
A. Ribosomes
B. A membrane-bound nucleus
C. A plasma membrane
D. DNA
Correct Answer: B
Rationale: Eukaryotic cells are defined by the presence of a membrane-bound
nucleus and specialized organelles. Prokaryotic cells lack these structures .
,5. At a generalized level, all cells are comprised of which four macromolecules?
A. Proteins, Lipids, Nucleic acids, and Polysaccharides
B. Proteins, Carbohydrates, Vitamins, and Minerals
C. Lipids, Nucleic acids, Water, and Salts
D. Proteins, Lipids, Carbohydrates, and Water
Correct Answer: A
Rationale: All cells are comprised of proteins, lipids, nucleic acids, and
polysaccharides (carbohydrates). These are the four main types of macromolecules
essential for cellular structure and function .
6. How many different types of amino acids are available for cells to build
proteins?
A. 4
B. 10
C. 20
D. 64
Correct Answer: C
Rationale: There are 20 standard amino acids that serve as the monomers for
proteins. The specific sequence of these amino acids determines a protein's unique
structure and function .
7. How many amino acids are classified as essential amino acids?
, A. 4
B. 9
C. 11
D. 20
Correct Answer: B
Rationale: There are 9 essential amino acids that cannot be synthesized by the
human body and must be obtained through diet .
8. The plasma membrane (select all that are true):
A. Restricts movement of materials in and out of the cell
B. Is often a triple layer comprised of lipids
C. Prevents essential nutrients from escaping
D. Contains hydrophobic tails pointing outward
Correct Answer: A, C
Rationale: The plasma membrane restricts movement of materials both in and out of
the cell and prevents essential nutrients from escaping. It is a bilayer (not triple layer)
comprised of lipids with hydrophobic tails pointing inward .
9. Complete the following DNA strand: 3' GGTCATCG 5' → 5' ___ 3'
A. 5' CCAGTAGC 3'
B. 5' CCAGCTAG 3'
C. 5' CCATGAGC 3'
D. 5' CCTAGTGC 3'
Correct Answer: A
COMPREHENSIVE EXAM BANK QUESTIONS &
ANSWERS | ALL MODULES 1-8 | 2026 EDITION
SECTION 1: CELL STRUCTURE & MICROBIAL
CLASSIFICATION
Questions 1-25
1. Which of the following is considered a "microbe" but is NOT classified as a
"microorganism"?
A. Bacteria
B. Archaea
C. Viruses
D. Fungi
Correct Answer: C
Rationale: Viruses lack cellular structure and cannot replicate outside of a host cell,
making them non-living. They are considered microbes but not microorganisms,
which must be living organisms .
2. Which of the following is the smallest biological unit of life?
A. Atom
B. Molecule
C. Cell
D. Tissue
,Correct Answer: C
Rationale: While atoms and molecules are smaller, the cell is the smallest unit that
can carry out all life processes independently, including metabolism and
reproduction .
3. Prokaryotic cells are characterized by the absence of:
A. A plasma membrane
B. DNA
C. A nucleus
D. Ribosomes
Correct Answer: C
Rationale: Prokaryotic cells lack a membrane-bound nucleus; their genetic material
is located in the nucleoid region. They do contain DNA, ribosomes, and a plasma
membrane .
4. Eukaryotic cells contain which of the following structures that prokaryotic
cells lack?
A. Ribosomes
B. A membrane-bound nucleus
C. A plasma membrane
D. DNA
Correct Answer: B
Rationale: Eukaryotic cells are defined by the presence of a membrane-bound
nucleus and specialized organelles. Prokaryotic cells lack these structures .
,5. At a generalized level, all cells are comprised of which four macromolecules?
A. Proteins, Lipids, Nucleic acids, and Polysaccharides
B. Proteins, Carbohydrates, Vitamins, and Minerals
C. Lipids, Nucleic acids, Water, and Salts
D. Proteins, Lipids, Carbohydrates, and Water
Correct Answer: A
Rationale: All cells are comprised of proteins, lipids, nucleic acids, and
polysaccharides (carbohydrates). These are the four main types of macromolecules
essential for cellular structure and function .
6. How many different types of amino acids are available for cells to build
proteins?
A. 4
B. 10
C. 20
D. 64
Correct Answer: C
Rationale: There are 20 standard amino acids that serve as the monomers for
proteins. The specific sequence of these amino acids determines a protein's unique
structure and function .
7. How many amino acids are classified as essential amino acids?
, A. 4
B. 9
C. 11
D. 20
Correct Answer: B
Rationale: There are 9 essential amino acids that cannot be synthesized by the
human body and must be obtained through diet .
8. The plasma membrane (select all that are true):
A. Restricts movement of materials in and out of the cell
B. Is often a triple layer comprised of lipids
C. Prevents essential nutrients from escaping
D. Contains hydrophobic tails pointing outward
Correct Answer: A, C
Rationale: The plasma membrane restricts movement of materials both in and out of
the cell and prevents essential nutrients from escaping. It is a bilayer (not triple layer)
comprised of lipids with hydrophobic tails pointing inward .
9. Complete the following DNA strand: 3' GGTCATCG 5' → 5' ___ 3'
A. 5' CCAGTAGC 3'
B. 5' CCAGCTAG 3'
C. 5' CCATGAGC 3'
D. 5' CCTAGTGC 3'
Correct Answer: A
