BIO 252 Physiology Exam Questions with
Correct Answers (VerifiedAnswers) Plus
Rationales 2026 Q&A Instant Download PDF
1. Which statement best describes the primary function of the
plasma membrane in a physiological system?
A. It produces all cellular ATP
B. It stores genetic information
C. It regulates movement of substances into and out of the cell
D. It synthesizes ribosomal RNA
Correct answer: C. It regulates movement of substances into
and out of the cell
The plasma membrane is a selectively permeable barrier
composed primarily of phospholipids, proteins, cholesterol, and
carbohydrates. Its selective permeability allows cells to maintain
different concentrations of ions and molecules inside and
outside the cell. Membrane proteins provide channels, carriers,
receptors, and pumps that are essential for communication,
transport, and maintenance of cellular homeostasis.
2. Which mechanism moves a substance down its
concentration gradient without requiring cellular ATP?
,A. Primary active transport
B. Secondary active transport
C. Facilitated diffusion
D. Endocytosis
Correct answer: C. Facilitated diffusion
Facilitated diffusion is a passive transport mechanism, meaning
that it does not directly require ATP. Molecules move from an
area of higher concentration toward an area of lower
concentration through membrane proteins such as channels or
carrier proteins. Although proteins are involved, the movement
is still passive because the driving force is the concentration or
electrochemical gradient.
3. Which ion is primarily responsible for establishing the
resting membrane potential of most neurons?
A. Calcium
B. Potassium
C. Sodium
D. Chloride
Correct answer: B. Potassium
Potassium plays the dominant role in establishing the resting
membrane potential because the resting membrane has
relatively high permeability to K⁺ through potassium leak
,channels. Potassium tends to diffuse out of the cell down its
concentration gradient, leaving the inside relatively negative.
Sodium and other ions also contribute, but potassium
permeability is the major determinant of the resting potential.
4. What is the major function of the sodium-potassium pump?
A. Transport three potassium ions out and two sodium ions into
the cell
B. Transport two sodium ions out and three potassium ions into
the cell
C. Transport three sodium ions out and two potassium ions into
the cell
D. Transport calcium into the cell and sodium out of the cell
Correct answer: C. Transport three sodium ions out and two
potassium ions into the cell
The sodium-potassium ATPase uses ATP to transport three Na⁺
ions from the cell and two K⁺ ions into the cell during each pump
cycle. This establishes and maintains the sodium and potassium
concentration gradients that are essential for resting membrane
potential, action potentials, and secondary active transport.
Because more positive charge leaves than enters, the pump also
has a small electrogenic effect.
, 5. Which organelle is primarily responsible for producing ATP
through aerobic cellular respiration?
A. Lysosome
B. Golgi apparatus
C. Mitochondrion
D. Nucleus
Correct answer: C. Mitochondrion
The mitochondria are the principal sites of aerobic ATP
production in most cells. They contain enzymes involved in the
citric acid cycle and an electron transport chain located in the
inner mitochondrial membrane. The electron transport chain
establishes a proton gradient that drives ATP synthesis through
oxidative phosphorylation.
6. Which division of the autonomic nervous system generally
increases heart rate?
A. Parasympathetic division
B. Sympathetic division
C. Somatic division
D. Enteric division only
Correct answer: B. Sympathetic division
Sympathetic stimulation generally increases heart rate and
cardiac contractility as part of the body's response to stress or
Correct Answers (VerifiedAnswers) Plus
Rationales 2026 Q&A Instant Download PDF
1. Which statement best describes the primary function of the
plasma membrane in a physiological system?
A. It produces all cellular ATP
B. It stores genetic information
C. It regulates movement of substances into and out of the cell
D. It synthesizes ribosomal RNA
Correct answer: C. It regulates movement of substances into
and out of the cell
The plasma membrane is a selectively permeable barrier
composed primarily of phospholipids, proteins, cholesterol, and
carbohydrates. Its selective permeability allows cells to maintain
different concentrations of ions and molecules inside and
outside the cell. Membrane proteins provide channels, carriers,
receptors, and pumps that are essential for communication,
transport, and maintenance of cellular homeostasis.
2. Which mechanism moves a substance down its
concentration gradient without requiring cellular ATP?
,A. Primary active transport
B. Secondary active transport
C. Facilitated diffusion
D. Endocytosis
Correct answer: C. Facilitated diffusion
Facilitated diffusion is a passive transport mechanism, meaning
that it does not directly require ATP. Molecules move from an
area of higher concentration toward an area of lower
concentration through membrane proteins such as channels or
carrier proteins. Although proteins are involved, the movement
is still passive because the driving force is the concentration or
electrochemical gradient.
3. Which ion is primarily responsible for establishing the
resting membrane potential of most neurons?
A. Calcium
B. Potassium
C. Sodium
D. Chloride
Correct answer: B. Potassium
Potassium plays the dominant role in establishing the resting
membrane potential because the resting membrane has
relatively high permeability to K⁺ through potassium leak
,channels. Potassium tends to diffuse out of the cell down its
concentration gradient, leaving the inside relatively negative.
Sodium and other ions also contribute, but potassium
permeability is the major determinant of the resting potential.
4. What is the major function of the sodium-potassium pump?
A. Transport three potassium ions out and two sodium ions into
the cell
B. Transport two sodium ions out and three potassium ions into
the cell
C. Transport three sodium ions out and two potassium ions into
the cell
D. Transport calcium into the cell and sodium out of the cell
Correct answer: C. Transport three sodium ions out and two
potassium ions into the cell
The sodium-potassium ATPase uses ATP to transport three Na⁺
ions from the cell and two K⁺ ions into the cell during each pump
cycle. This establishes and maintains the sodium and potassium
concentration gradients that are essential for resting membrane
potential, action potentials, and secondary active transport.
Because more positive charge leaves than enters, the pump also
has a small electrogenic effect.
, 5. Which organelle is primarily responsible for producing ATP
through aerobic cellular respiration?
A. Lysosome
B. Golgi apparatus
C. Mitochondrion
D. Nucleus
Correct answer: C. Mitochondrion
The mitochondria are the principal sites of aerobic ATP
production in most cells. They contain enzymes involved in the
citric acid cycle and an electron transport chain located in the
inner mitochondrial membrane. The electron transport chain
establishes a proton gradient that drives ATP synthesis through
oxidative phosphorylation.
6. Which division of the autonomic nervous system generally
increases heart rate?
A. Parasympathetic division
B. Sympathetic division
C. Somatic division
D. Enteric division only
Correct answer: B. Sympathetic division
Sympathetic stimulation generally increases heart rate and
cardiac contractility as part of the body's response to stress or
