,Portage Learning CHEM 103 General
Chemistry I Module 3 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
Which of the following cellular transport mechanisms requires ATP hydrolysis to move
sodium ions out of the cell against a steep concentration gradient?
A) Facilitated diffusion via leak channels
B) Simple diffusion through the phospholipid bilayer
C) Primary active transport via the \(\text{Na}^{+}/\text{K}^{+}\) ATPase pump
D) Secondary active transport via symporter channels
Answer: C) Primary active transport via the \(\text{Na}^{+}/\text{K}^{+}\) ATPase
pump
Rationale: The \(\text{Na}^{+}/\text{K}^{+}\) ATPase pump is a classic example of
primary active transport. It directly consumes ATP to pump three sodium ions out of the
cell and two potassium ions into the cell, maintaining vital electrochemical gradients.
Question 2
A patient presents with extreme lethargy, weight gain, and low core body temperature.
Blood tests confirm low levels of \(\text{T}_{3}\) and \(\text{T}_{4}\), but significantly
elevated levels of Thyroid-Stimulating Hormone (TSH). This profile point to a localized
functional defect in which structure?
A) Hypothalamus
B) Anterior pituitary gland
C) Thyroid gland
D) Posterior pituitary gland
Answer: C) Thyroid gland
Rationale: Because TSH levels are elevated, the anterior pituitary is responding
appropriately to low thyroid hormone levels. The lack of negative feedback inhibition
means the thyroid gland itself is failing to produce \(\text{T}_{3}\) and \(\text{T}_{4}\)
(primary hypothyroidism).
, Question 3
Which specific cell layer of the epidermis contains tactile Merkel cells and is firmly
anchored to the underlying dermis via hemidesmosomes?
A) Stratum corneum
B) Stratum lucidum
C) Stratum spinosum
D) Stratum basale
Answer: D) Stratum basale
Rationale: The stratum basale is the deepest epidermal layer. It consists of a single row
of cuboidal stem cells attached to the basement membrane by hemidesmosomes,
interspersed with Merkel cells and melanocytes.
Question 4
During the absolute refractory period of a neuronal action potential, why is it completely
impossible for a second stimulus to initiate another nerve impulse?
A) Voltage-gated potassium channels are locked in an open state.
B) Voltage-gated sodium channels are inactivated by their inactivation gates.
C) Ligand-gated chloride channels have hyperpolarized the membrane.
D) The sodium-potassium pump has ceased operating.
Answer: B) Voltage-gated sodium channels are inactivated by their inactivation
gates.
Rationale: The absolute refractory period spans from the opening of voltage-gated
\(\text{Na}^{+}\) channels until they reset to their resting state. During this time, the
inactivation gates are closed, making the channels unresponsive to any stimulus.
Question 5
Which of the following structural joints is classified structurally as a fibrous syndesmosis
and functionally as an amphiarthrosis?
A) Intervertebral disc symphysis
B) Sagittal suture of the skull
C) Interosseous membrane between the radius and ulna
D) Epiphyseal growth plate
Answer: C) Interosseous membrane between the radius and ulna
Rationale: A syndesmosis is a fibrous joint bound together by a dense regular ligament
or interosseous sheet. Because it permits slight movement, its functional classification is
an amphiarthrosis.
Question 6
What specific structural component of a thin filament acts as a calcium-binding receptor,
shifting configuration to move tropomyosin out of the way?
Chemistry I Module 3 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
Which of the following cellular transport mechanisms requires ATP hydrolysis to move
sodium ions out of the cell against a steep concentration gradient?
A) Facilitated diffusion via leak channels
B) Simple diffusion through the phospholipid bilayer
C) Primary active transport via the \(\text{Na}^{+}/\text{K}^{+}\) ATPase pump
D) Secondary active transport via symporter channels
Answer: C) Primary active transport via the \(\text{Na}^{+}/\text{K}^{+}\) ATPase
pump
Rationale: The \(\text{Na}^{+}/\text{K}^{+}\) ATPase pump is a classic example of
primary active transport. It directly consumes ATP to pump three sodium ions out of the
cell and two potassium ions into the cell, maintaining vital electrochemical gradients.
Question 2
A patient presents with extreme lethargy, weight gain, and low core body temperature.
Blood tests confirm low levels of \(\text{T}_{3}\) and \(\text{T}_{4}\), but significantly
elevated levels of Thyroid-Stimulating Hormone (TSH). This profile point to a localized
functional defect in which structure?
A) Hypothalamus
B) Anterior pituitary gland
C) Thyroid gland
D) Posterior pituitary gland
Answer: C) Thyroid gland
Rationale: Because TSH levels are elevated, the anterior pituitary is responding
appropriately to low thyroid hormone levels. The lack of negative feedback inhibition
means the thyroid gland itself is failing to produce \(\text{T}_{3}\) and \(\text{T}_{4}\)
(primary hypothyroidism).
, Question 3
Which specific cell layer of the epidermis contains tactile Merkel cells and is firmly
anchored to the underlying dermis via hemidesmosomes?
A) Stratum corneum
B) Stratum lucidum
C) Stratum spinosum
D) Stratum basale
Answer: D) Stratum basale
Rationale: The stratum basale is the deepest epidermal layer. It consists of a single row
of cuboidal stem cells attached to the basement membrane by hemidesmosomes,
interspersed with Merkel cells and melanocytes.
Question 4
During the absolute refractory period of a neuronal action potential, why is it completely
impossible for a second stimulus to initiate another nerve impulse?
A) Voltage-gated potassium channels are locked in an open state.
B) Voltage-gated sodium channels are inactivated by their inactivation gates.
C) Ligand-gated chloride channels have hyperpolarized the membrane.
D) The sodium-potassium pump has ceased operating.
Answer: B) Voltage-gated sodium channels are inactivated by their inactivation
gates.
Rationale: The absolute refractory period spans from the opening of voltage-gated
\(\text{Na}^{+}\) channels until they reset to their resting state. During this time, the
inactivation gates are closed, making the channels unresponsive to any stimulus.
Question 5
Which of the following structural joints is classified structurally as a fibrous syndesmosis
and functionally as an amphiarthrosis?
A) Intervertebral disc symphysis
B) Sagittal suture of the skull
C) Interosseous membrane between the radius and ulna
D) Epiphyseal growth plate
Answer: C) Interosseous membrane between the radius and ulna
Rationale: A syndesmosis is a fibrous joint bound together by a dense regular ligament
or interosseous sheet. Because it permits slight movement, its functional classification is
an amphiarthrosis.
Question 6
What specific structural component of a thin filament acts as a calcium-binding receptor,
shifting configuration to move tropomyosin out of the way?
