1
PHYS 261 Human Physiology Combined
Quizzes 1–4 | 2026/2027 | 160 Questions and
Correct Answers | Complete Exam Material.
QUIZ 1: CELLULAR PHYSIOLOGY, MEMBRANE TRANSPORT & HOMEOSTASIS (40 Questions)
1. Which of the following best describes a negative feedback mechanism?
A. The stretch of the cervix during labor causes contractions, which further stretch the cervix.
B. A clotting factor activates another clotting factor, forming a clot.
C. An increase in blood glucose stimulates insulin release, which lowers blood glucose.
D. Depolarization of a neuron opens voltage-gated Na+ channels, causing further
depolarization.
Answer: C
[CORRECT] Negative feedback loops work to reverse the direction of a change, bringing the
variable back to the set point. In this case, insulin lowers blood glucose, counteracting the
initial increase.
2. Which component of the plasma membrane is primarily responsible for limiting the
movement of water-soluble molecules and ions?
A. Integral proteins
B. Phospholipid bilayer
C. Cholesterol
D. Glycoproteins
Answer: B
, 2
[CORRECT] The phospholipid bilayer forms a hydrophobic core that acts as a barrier to the
passage of water-soluble (hydrophilic) molecules and ions, preventing them from freely
crossing the membrane.
3. In a hypertonic solution, a red blood cell will:
A. Swell and potentially lyse.
B. Shrink (crenate).
C. Remain the same size.
D. Increase its metabolic rate.
Answer: B
[CORRECT] In a hypertonic solution, the extracellular fluid has a higher solute concentration
than the intracellular fluid. Water moves out of the cell via osmosis to the area of higher
solute concentration, causing the cell to shrink.
4. Which of the following is a characteristic of simple diffusion?
A. Requires energy in the form of ATP.
B. Moves molecules from an area of low concentration to high concentration.
C. Requires a protein carrier or channel.
D. Is directly proportional to the concentration gradient.
Answer: D
[CORRECT] Simple diffusion is the passive movement of molecules down their concentration
gradient (from high to low). The rate is directly proportional to the magnitude of the
concentration gradient.
5. The Na+-K+ ATPase pump is essential for maintaining the resting membrane potential
because it:
, 3
A. Pumps 3 Na+ in and 2 K+ out.
B. Creates an electrochemical gradient used to drive secondary active transport.
C. Is directly responsible for the action potential upstroke.
D. Allows Cl- to enter the cell.
Answer: B
[CORRECT] By pumping 3 Na+ out and 2 K+ in, the pump creates concentration gradients for
both ions. These gradients store potential energy used to drive secondary active transport
(e.g., glucose symport) and maintain the resting membrane potential.
6. A molecule is transported into the cell against its concentration gradient using the energy
derived from the simultaneous movement of Na+ down its electrochemical gradient. This is
an example of:
A. Primary active transport.
B. Facilitated diffusion.
C. Secondary active transport (cotransport).
D. Osmosis.
Answer: C
[CORRECT] Secondary active transport uses the energy stored in an ion gradient (usually Na+)
established by primary active transport to move another molecule against its gradient.
7. Which of the following ions has the highest permeability across the resting neuronal
membrane, primarily determining the resting membrane potential?
A. Na+
B. K+
C. Cl-
D. Ca2+
, 4
Answer: B
[CORRECT] At rest, the membrane is much more permeable to K+ than to Na+ or other ions
due to the presence of many leak channels for K+. The outward diffusion of K+ establishes the
negative resting membrane potential (approx. -70 mV).
8. According to the Nernst equation, if the intracellular concentration of K+ is higher than the
extracellular concentration, the equilibrium potential (E_K) for K+ will be:
A. Positive
B. Negative
C. Zero
D. Equal to the resting membrane potential
Answer: B
[CORRECT] The Nernst equation calculates the equilibrium potential based on concentration
ratios. Since K+ is more concentrated inside the cell, the chemical force drives K+ out; to
balance this, the inside must be negative (approx. -90 mV).
9. The Goldman-Hodgkin-Katz (GHK) equation differs from the Nernst equation because it:
A. Calculates the membrane potential based on the contributions of multiple permeable ions.
B. Only considers the concentration of Na+.
C. Requires ATP.
D. Describes the movement of water across the membrane.
Answer: A
[CORRECT] While the Nernst equation calculates the equilibrium potential for a single ion, the
GHK equation calculates the resting membrane potential based on the concentrations and
relative membrane permeabilities of all major ions (K+, Na+, Cl-).
PHYS 261 Human Physiology Combined
Quizzes 1–4 | 2026/2027 | 160 Questions and
Correct Answers | Complete Exam Material.
QUIZ 1: CELLULAR PHYSIOLOGY, MEMBRANE TRANSPORT & HOMEOSTASIS (40 Questions)
1. Which of the following best describes a negative feedback mechanism?
A. The stretch of the cervix during labor causes contractions, which further stretch the cervix.
B. A clotting factor activates another clotting factor, forming a clot.
C. An increase in blood glucose stimulates insulin release, which lowers blood glucose.
D. Depolarization of a neuron opens voltage-gated Na+ channels, causing further
depolarization.
Answer: C
[CORRECT] Negative feedback loops work to reverse the direction of a change, bringing the
variable back to the set point. In this case, insulin lowers blood glucose, counteracting the
initial increase.
2. Which component of the plasma membrane is primarily responsible for limiting the
movement of water-soluble molecules and ions?
A. Integral proteins
B. Phospholipid bilayer
C. Cholesterol
D. Glycoproteins
Answer: B
, 2
[CORRECT] The phospholipid bilayer forms a hydrophobic core that acts as a barrier to the
passage of water-soluble (hydrophilic) molecules and ions, preventing them from freely
crossing the membrane.
3. In a hypertonic solution, a red blood cell will:
A. Swell and potentially lyse.
B. Shrink (crenate).
C. Remain the same size.
D. Increase its metabolic rate.
Answer: B
[CORRECT] In a hypertonic solution, the extracellular fluid has a higher solute concentration
than the intracellular fluid. Water moves out of the cell via osmosis to the area of higher
solute concentration, causing the cell to shrink.
4. Which of the following is a characteristic of simple diffusion?
A. Requires energy in the form of ATP.
B. Moves molecules from an area of low concentration to high concentration.
C. Requires a protein carrier or channel.
D. Is directly proportional to the concentration gradient.
Answer: D
[CORRECT] Simple diffusion is the passive movement of molecules down their concentration
gradient (from high to low). The rate is directly proportional to the magnitude of the
concentration gradient.
5. The Na+-K+ ATPase pump is essential for maintaining the resting membrane potential
because it:
, 3
A. Pumps 3 Na+ in and 2 K+ out.
B. Creates an electrochemical gradient used to drive secondary active transport.
C. Is directly responsible for the action potential upstroke.
D. Allows Cl- to enter the cell.
Answer: B
[CORRECT] By pumping 3 Na+ out and 2 K+ in, the pump creates concentration gradients for
both ions. These gradients store potential energy used to drive secondary active transport
(e.g., glucose symport) and maintain the resting membrane potential.
6. A molecule is transported into the cell against its concentration gradient using the energy
derived from the simultaneous movement of Na+ down its electrochemical gradient. This is
an example of:
A. Primary active transport.
B. Facilitated diffusion.
C. Secondary active transport (cotransport).
D. Osmosis.
Answer: C
[CORRECT] Secondary active transport uses the energy stored in an ion gradient (usually Na+)
established by primary active transport to move another molecule against its gradient.
7. Which of the following ions has the highest permeability across the resting neuronal
membrane, primarily determining the resting membrane potential?
A. Na+
B. K+
C. Cl-
D. Ca2+
, 4
Answer: B
[CORRECT] At rest, the membrane is much more permeable to K+ than to Na+ or other ions
due to the presence of many leak channels for K+. The outward diffusion of K+ establishes the
negative resting membrane potential (approx. -70 mV).
8. According to the Nernst equation, if the intracellular concentration of K+ is higher than the
extracellular concentration, the equilibrium potential (E_K) for K+ will be:
A. Positive
B. Negative
C. Zero
D. Equal to the resting membrane potential
Answer: B
[CORRECT] The Nernst equation calculates the equilibrium potential based on concentration
ratios. Since K+ is more concentrated inside the cell, the chemical force drives K+ out; to
balance this, the inside must be negative (approx. -90 mV).
9. The Goldman-Hodgkin-Katz (GHK) equation differs from the Nernst equation because it:
A. Calculates the membrane potential based on the contributions of multiple permeable ions.
B. Only considers the concentration of Na+.
C. Requires ATP.
D. Describes the movement of water across the membrane.
Answer: A
[CORRECT] While the Nernst equation calculates the equilibrium potential for a single ion, the
GHK equation calculates the resting membrane potential based on the concentrations and
relative membrane permeabilities of all major ions (K+, Na+, Cl-).
