PCB3023C Exam 2: Cell Biology 2026 – FGCU
1. Which of the following transport mechanisms requires energy to move a
solute against its electrochemical gradient?
A. Simple diffusion
B. Passive transport
C. Facilitated diffusion
D. Active transport
Answer: D
Rationale: Active transport uses energy (often ATP) to move molecules against their
concentration or electrochemical gradient.
2. The sodium-potassium pump (Na+/K+ ATPase) functions by pumping:
A. 2 Na+ out and 3 K+ in
B. 2 Na+ in and 3 K+ out
C. 3 Na+ in and 2 K+ out
D. 3 Na+ out and 2 K+ in
Answer: D
Rationale: The Na+/K+ pump maintains the electrochemical gradient by moving three
sodium ions out of the cell for every two potassium ions moved in.
,3. Which ion is typically found at a much higher concentration outside a
mammalian cell than inside?
A. Na+
B. K+
C. Mg2+
D. H+
Answer: A
Rationale: Sodium (Na+) concentrations are significantly higher in the extracellular fluid
compared to the cytosol.
4. What is the primary function of aquaporins in the plasma membrane?
A. Facilitating the rapid movement of water
B. Transporting glucose
C. Pumping protons
D. Maintaining resting membrane potential
Answer: A
Rationale: Aquaporins are specialized channel proteins that allow water molecules to
cross the membrane more rapidly than via simple diffusion.
5. A symport is a type of coupled transporter that:
A. Moves one solute in one direction
B. Moves two solutes in opposite directions
C. Moves two solutes in the same direction
D. Does not require a concentration gradient
Answer: C
Rationale: Symporters move two different types of solutes across the membrane in the
same direction.
, 6. Which of the following is responsible for the negative resting membrane
potential of most animal cells?
A. Outward leakage of K+
B. Inward leakage of Na+
C. Inward movement of Cl-
D. Outward movement of Ca2+
Answer: A
Rationale: The resting membrane potential is primarily established by K+ leak channels
allowing K+ to move out of the cell down its concentration gradient.
7. G-protein coupled receptors (GPCRs) typically consist of how many
transmembrane alpha-helices?
A. One
B. Three
C. Twelve
D. Seven
Answer: D
Rationale: GPCRs are characterized by a single polypeptide chain that passes through the
lipid bilayer seven times.
8. In the cAMP signaling pathway, which enzyme is responsible for converting
ATP to cyclic AMP?
A. Phosphodiesterase
B. Adenylyl cyclase
C. Protein Kinase A
D. G-protein
Answer: B
Rationale: Adenylyl cyclase is the membrane-bound enzyme that catalyzes the formation
of cAMP from ATP.
1. Which of the following transport mechanisms requires energy to move a
solute against its electrochemical gradient?
A. Simple diffusion
B. Passive transport
C. Facilitated diffusion
D. Active transport
Answer: D
Rationale: Active transport uses energy (often ATP) to move molecules against their
concentration or electrochemical gradient.
2. The sodium-potassium pump (Na+/K+ ATPase) functions by pumping:
A. 2 Na+ out and 3 K+ in
B. 2 Na+ in and 3 K+ out
C. 3 Na+ in and 2 K+ out
D. 3 Na+ out and 2 K+ in
Answer: D
Rationale: The Na+/K+ pump maintains the electrochemical gradient by moving three
sodium ions out of the cell for every two potassium ions moved in.
,3. Which ion is typically found at a much higher concentration outside a
mammalian cell than inside?
A. Na+
B. K+
C. Mg2+
D. H+
Answer: A
Rationale: Sodium (Na+) concentrations are significantly higher in the extracellular fluid
compared to the cytosol.
4. What is the primary function of aquaporins in the plasma membrane?
A. Facilitating the rapid movement of water
B. Transporting glucose
C. Pumping protons
D. Maintaining resting membrane potential
Answer: A
Rationale: Aquaporins are specialized channel proteins that allow water molecules to
cross the membrane more rapidly than via simple diffusion.
5. A symport is a type of coupled transporter that:
A. Moves one solute in one direction
B. Moves two solutes in opposite directions
C. Moves two solutes in the same direction
D. Does not require a concentration gradient
Answer: C
Rationale: Symporters move two different types of solutes across the membrane in the
same direction.
, 6. Which of the following is responsible for the negative resting membrane
potential of most animal cells?
A. Outward leakage of K+
B. Inward leakage of Na+
C. Inward movement of Cl-
D. Outward movement of Ca2+
Answer: A
Rationale: The resting membrane potential is primarily established by K+ leak channels
allowing K+ to move out of the cell down its concentration gradient.
7. G-protein coupled receptors (GPCRs) typically consist of how many
transmembrane alpha-helices?
A. One
B. Three
C. Twelve
D. Seven
Answer: D
Rationale: GPCRs are characterized by a single polypeptide chain that passes through the
lipid bilayer seven times.
8. In the cAMP signaling pathway, which enzyme is responsible for converting
ATP to cyclic AMP?
A. Phosphodiesterase
B. Adenylyl cyclase
C. Protein Kinase A
D. G-protein
Answer: B
Rationale: Adenylyl cyclase is the membrane-bound enzyme that catalyzes the formation
of cAMP from ATP.
