BIOL 271 / BIOL271 Module 2: (Latest 2026/2027
Update) Verified Questions & Answers with Detailed
Rationales | Grade A
SUBTITLE:
50 Exam Questions with Answers & Detailed Rationales
PREPARED FOR:
[BIOL 271 Module 2]
DOCUMENT INCLUDES:
● Exam-style questions
● Correct answers
● Detailed rationales
● Key topics covered
TOPICS COVERED:
● Respiratory System (Anatomy & Physiology)
● Digestive System (Anatomy & Physiology)
● Urinary System (Anatomy & Physiology)
● Reproductive System (Male & Female)
● Fluid, Electrolyte, and Acid-Base Balance
● Metabolism & Nutrition
● Endocrine System (Advanced Integration)
PURPOSE:
This comprehensive Module 2 review guide is designed to help BIOL 271 students
master essential biological concepts, reinforce their understanding of key mechanisms
and processes, and confidently prepare for the latest 2026/2027 module examinations.
,SECTION 1: Respiratory System
Question 1
Which structure is responsible for the majority of gas exchange in the lungs?
A. Trachea
B. Primary bronchi
C. Alveoli
D. Terminal bronchioles
Correct Answer: C
Rationale: The alveoli are the tiny, thin-walled air sacs at the terminal ends of the
respiratory tree where the vast majority of gas exchange occurs. Their walls are
composed of simple squamous epithelium (Type I pneumocytes), and they are
surrounded by an extensive capillary network, creating an extremely thin respiratory
membrane (approximately 0.5 micrometers) that facilitates rapid diffusion of O₂ and
CO₂. The trachea (A) serves as a conducting airway with cartilage rings for support but
lacks the thin membrane necessary for gas exchange. The primary bronchi (B) are also
conducting airways with thicker walls and no alveoli. Terminal bronchioles (D) are the
last part of the conducting zone and contain smooth muscle for regulation of airflow
but do not participate in gas exchange.
Question 2
During quiet breathing, which muscle is the primary muscle responsible for inspiration?
A. Internal intercostals
B. External intercostals
C. Diaphragm
D. Abdominal muscles
,Correct Answer: C
Rationale: The diaphragm is the primary muscle of inspiration during quiet breathing.
When it contracts, it flattens and descends, increasing the thoracic volume and
decreasing intrathoracic pressure, which draws air into the lungs. The external
intercostals (B) assist by elevating the ribs, but they are accessory muscles rather than
the primary driver. The internal intercostals (A) and abdominal muscles (D) are primarily
involved in forced expiration, not inspiration. During forced inspiration, accessory
muscles like the sternocleidomastoid and scalenes become active, but the diaphragm
remains the dominant muscle.
Question 3
What is the partial pressure of oxygen (PO₂) in alveolar air at sea level?
A. 40 mmHg
B. 45 mmHg
C. 100 mmHg
D. 104 mmHg
Correct Answer: D
Rationale: The partial pressure of oxygen in alveolar air at sea level is approximately 104
mmHg (or ~100 mmHg depending on the source, but 104 mmHg is the more precise
calculated value using the alveolar gas equation). This is lower than the PO₂ of inspired
dry air (159 mmHg) because oxygen is diluted by water vapor (47 mmHg) and carbon
dioxide in the alveoli, and some oxygen is absorbed into the blood. The PO₂ of venous
blood is about 40 mmHg (A), and the PCO₂ of arterial blood is about 45 mmHg (B). The
PO₂ of arterial blood is approximately 100 mmHg (C), which is close to but slightly lower
than alveolar PO₂ due to the normal alveolar-arterial (A-a) gradient.
Question 4
, Which of the following correctly describes the relationship between hemoglobin and
oxygen at the tissue level?
A. High pH, low PCO₂, and high temperature increase oxygen binding to hemoglobin
B. Low pH, high PCO₂, and high temperature decrease oxygen binding to hemoglobin
C. High pH, low PCO₂, and low temperature decrease oxygen binding to hemoglobin
D. Low pH, low PCO₂, and high temperature increase oxygen binding to hemoglobin
Correct Answer: B
Rationale: At the tissue level, conditions of low pH (acidic environment), high PCO₂, and
high temperature all promote the release of oxygen from hemoglobin. This is known as
the Bohr effect and is related to the rightward shift of the oxygen-hemoglobin
dissociation curve. Active metabolizing tissues produce CO₂ (which forms carbonic
acid, lowering pH) and heat, creating an environment that reduces hemoglobin's affinity
for oxygen and facilitates O₂ unloading. Option A describes conditions that would
increase oxygen binding (left shift), which occurs in the lungs where pH is higher, PCO₂
is lower, and temperature is lower. Option C is incorrect because high pH and low PCO₂
increase binding, not decrease it. Option D is incorrect because low PCO₂ would
increase binding, not decrease it.
Question 5
The Hering-Breuer reflex is responsible for which of the following?
A. Increasing heart rate during exercise
B. Preventing overinflation of the lungs
C. Stimulating the cough reflex
D. Regulating blood pressure
Correct Answer: B
Update) Verified Questions & Answers with Detailed
Rationales | Grade A
SUBTITLE:
50 Exam Questions with Answers & Detailed Rationales
PREPARED FOR:
[BIOL 271 Module 2]
DOCUMENT INCLUDES:
● Exam-style questions
● Correct answers
● Detailed rationales
● Key topics covered
TOPICS COVERED:
● Respiratory System (Anatomy & Physiology)
● Digestive System (Anatomy & Physiology)
● Urinary System (Anatomy & Physiology)
● Reproductive System (Male & Female)
● Fluid, Electrolyte, and Acid-Base Balance
● Metabolism & Nutrition
● Endocrine System (Advanced Integration)
PURPOSE:
This comprehensive Module 2 review guide is designed to help BIOL 271 students
master essential biological concepts, reinforce their understanding of key mechanisms
and processes, and confidently prepare for the latest 2026/2027 module examinations.
,SECTION 1: Respiratory System
Question 1
Which structure is responsible for the majority of gas exchange in the lungs?
A. Trachea
B. Primary bronchi
C. Alveoli
D. Terminal bronchioles
Correct Answer: C
Rationale: The alveoli are the tiny, thin-walled air sacs at the terminal ends of the
respiratory tree where the vast majority of gas exchange occurs. Their walls are
composed of simple squamous epithelium (Type I pneumocytes), and they are
surrounded by an extensive capillary network, creating an extremely thin respiratory
membrane (approximately 0.5 micrometers) that facilitates rapid diffusion of O₂ and
CO₂. The trachea (A) serves as a conducting airway with cartilage rings for support but
lacks the thin membrane necessary for gas exchange. The primary bronchi (B) are also
conducting airways with thicker walls and no alveoli. Terminal bronchioles (D) are the
last part of the conducting zone and contain smooth muscle for regulation of airflow
but do not participate in gas exchange.
Question 2
During quiet breathing, which muscle is the primary muscle responsible for inspiration?
A. Internal intercostals
B. External intercostals
C. Diaphragm
D. Abdominal muscles
,Correct Answer: C
Rationale: The diaphragm is the primary muscle of inspiration during quiet breathing.
When it contracts, it flattens and descends, increasing the thoracic volume and
decreasing intrathoracic pressure, which draws air into the lungs. The external
intercostals (B) assist by elevating the ribs, but they are accessory muscles rather than
the primary driver. The internal intercostals (A) and abdominal muscles (D) are primarily
involved in forced expiration, not inspiration. During forced inspiration, accessory
muscles like the sternocleidomastoid and scalenes become active, but the diaphragm
remains the dominant muscle.
Question 3
What is the partial pressure of oxygen (PO₂) in alveolar air at sea level?
A. 40 mmHg
B. 45 mmHg
C. 100 mmHg
D. 104 mmHg
Correct Answer: D
Rationale: The partial pressure of oxygen in alveolar air at sea level is approximately 104
mmHg (or ~100 mmHg depending on the source, but 104 mmHg is the more precise
calculated value using the alveolar gas equation). This is lower than the PO₂ of inspired
dry air (159 mmHg) because oxygen is diluted by water vapor (47 mmHg) and carbon
dioxide in the alveoli, and some oxygen is absorbed into the blood. The PO₂ of venous
blood is about 40 mmHg (A), and the PCO₂ of arterial blood is about 45 mmHg (B). The
PO₂ of arterial blood is approximately 100 mmHg (C), which is close to but slightly lower
than alveolar PO₂ due to the normal alveolar-arterial (A-a) gradient.
Question 4
, Which of the following correctly describes the relationship between hemoglobin and
oxygen at the tissue level?
A. High pH, low PCO₂, and high temperature increase oxygen binding to hemoglobin
B. Low pH, high PCO₂, and high temperature decrease oxygen binding to hemoglobin
C. High pH, low PCO₂, and low temperature decrease oxygen binding to hemoglobin
D. Low pH, low PCO₂, and high temperature increase oxygen binding to hemoglobin
Correct Answer: B
Rationale: At the tissue level, conditions of low pH (acidic environment), high PCO₂, and
high temperature all promote the release of oxygen from hemoglobin. This is known as
the Bohr effect and is related to the rightward shift of the oxygen-hemoglobin
dissociation curve. Active metabolizing tissues produce CO₂ (which forms carbonic
acid, lowering pH) and heat, creating an environment that reduces hemoglobin's affinity
for oxygen and facilitates O₂ unloading. Option A describes conditions that would
increase oxygen binding (left shift), which occurs in the lungs where pH is higher, PCO₂
is lower, and temperature is lower. Option C is incorrect because high pH and low PCO₂
increase binding, not decrease it. Option D is incorrect because low PCO₂ would
increase binding, not decrease it.
Question 5
The Hering-Breuer reflex is responsible for which of the following?
A. Increasing heart rate during exercise
B. Preventing overinflation of the lungs
C. Stimulating the cough reflex
D. Regulating blood pressure
Correct Answer: B
