BIOD 151 Gas Exchange Mastery Exam Oxygen
& Carbon Dioxide Transport | 100 Practice
Questions Portage Learning | Anatomy &
Physiology I | 2026/2027 Edition
This specialized practice exam focuses specifically on
the physiological transport of oxygen and carbon dioxide in
the blood—a critical component of BIOD 151 Module 2. Questions
are designed to test your mastery of hemoglobin function, gas
solubility, dissociation curves, enzymatic reactions, and the
intricate mechanisms that ensure efficient gas exchange at the
alveolar and tissue levels.
• Focus Areas: Hemoglobin-oxygen binding, oxyhemoglobin
dissociation curve, Bohr effect, Haldane effect, carbon dioxide
transport (bicarbonate, carbaminohemoglobin), chloride shift,
carbonic anhydrase, partial pressure gradients, internal vs.
external respiration, and gas solubility.
,SECTION A: MULTIPLE CHOICE QUESTIONS
(Questions 1–40)
Question 1
Oxygen is primarily transported in the blood:
A. Dissolved directly in plasma
B. Bound to hemoglobin in red blood cells
C. As bicarbonate ions
D. Bound to plasma proteins
Answer: B. Bound to hemoglobin in red blood cells
Expert Rationale: Approximately 98.5% of oxygen is transported
bound to hemoglobin within erythrocytes (RBCs). Only about
1.5% is dissolved directly in plasma. Hemoglobin's iron-
containing heme groups reversibly bind oxygen molecules.
Question 2
Carbon dioxide is primarily transported in the blood:
A. Dissolved directly in plasma
B. Bound to hemoglobin
C. As bicarbonate ions (HCO₃⁻)
D. As carbonic acid
Answer: C. As bicarbonate ions (HCO₃⁻)
Expert Rationale: Approximately 70% of CO₂ is transported as
bicarbonate ions in plasma. About 23% is bound to hemoglobin as
,carbaminohemoglobin, and only 7% is dissolved directly in
plasma.
Question 3
The iron atom in hemoglobin that binds oxygen is found in:
A. The globin protein chain
B. The heme group
C. The amino acid histidine
D. The bicarbonate molecule
Answer: B. The heme group
Expert Rationale: Each hemoglobin molecule contains four heme
groups, each with an iron atom (Fe²⁺) at its center. Oxygen
reversibly binds to these iron atoms. The globin protein chains
(alpha and beta) surround and protect the heme groups.
Question 4
How many oxygen molecules can a single hemoglobin molecule
carry?
A. 1
B. 2
C. 4
D. 8
Answer: C. 4
, Expert Rationale: Each hemoglobin molecule has four heme
groups, each capable of binding one oxygen molecule. Therefore,
one hemoglobin molecule can transport up to four O₂ molecules.
Question 5
The oxygen-hemoglobin dissociation curve is:
A. Linear
B. Sigmoidal (S-shaped)
C. Exponential
D. Hyperbolic
Answer: B. Sigmoidal (S-shaped)
Expert Rationale: The oxygen-hemoglobin dissociation curve is
sigmoidal due to cooperative binding. As the first oxygen
molecule binds, hemoglobin undergoes a conformational change
that increases the affinity for subsequent oxygen molecules,
creating the characteristic S-shape.
Question 6
The term "cooperative binding" in hemoglobin refers to:
A. Oxygen binding to plasma proteins
B. Increased oxygen affinity after the first oxygen binds
C. Hemoglobin binding to carbon dioxide
D. The exchange of chloride ions
Answer: B. Increased oxygen affinity after the first oxygen
binds
& Carbon Dioxide Transport | 100 Practice
Questions Portage Learning | Anatomy &
Physiology I | 2026/2027 Edition
This specialized practice exam focuses specifically on
the physiological transport of oxygen and carbon dioxide in
the blood—a critical component of BIOD 151 Module 2. Questions
are designed to test your mastery of hemoglobin function, gas
solubility, dissociation curves, enzymatic reactions, and the
intricate mechanisms that ensure efficient gas exchange at the
alveolar and tissue levels.
• Focus Areas: Hemoglobin-oxygen binding, oxyhemoglobin
dissociation curve, Bohr effect, Haldane effect, carbon dioxide
transport (bicarbonate, carbaminohemoglobin), chloride shift,
carbonic anhydrase, partial pressure gradients, internal vs.
external respiration, and gas solubility.
,SECTION A: MULTIPLE CHOICE QUESTIONS
(Questions 1–40)
Question 1
Oxygen is primarily transported in the blood:
A. Dissolved directly in plasma
B. Bound to hemoglobin in red blood cells
C. As bicarbonate ions
D. Bound to plasma proteins
Answer: B. Bound to hemoglobin in red blood cells
Expert Rationale: Approximately 98.5% of oxygen is transported
bound to hemoglobin within erythrocytes (RBCs). Only about
1.5% is dissolved directly in plasma. Hemoglobin's iron-
containing heme groups reversibly bind oxygen molecules.
Question 2
Carbon dioxide is primarily transported in the blood:
A. Dissolved directly in plasma
B. Bound to hemoglobin
C. As bicarbonate ions (HCO₃⁻)
D. As carbonic acid
Answer: C. As bicarbonate ions (HCO₃⁻)
Expert Rationale: Approximately 70% of CO₂ is transported as
bicarbonate ions in plasma. About 23% is bound to hemoglobin as
,carbaminohemoglobin, and only 7% is dissolved directly in
plasma.
Question 3
The iron atom in hemoglobin that binds oxygen is found in:
A. The globin protein chain
B. The heme group
C. The amino acid histidine
D. The bicarbonate molecule
Answer: B. The heme group
Expert Rationale: Each hemoglobin molecule contains four heme
groups, each with an iron atom (Fe²⁺) at its center. Oxygen
reversibly binds to these iron atoms. The globin protein chains
(alpha and beta) surround and protect the heme groups.
Question 4
How many oxygen molecules can a single hemoglobin molecule
carry?
A. 1
B. 2
C. 4
D. 8
Answer: C. 4
, Expert Rationale: Each hemoglobin molecule has four heme
groups, each capable of binding one oxygen molecule. Therefore,
one hemoglobin molecule can transport up to four O₂ molecules.
Question 5
The oxygen-hemoglobin dissociation curve is:
A. Linear
B. Sigmoidal (S-shaped)
C. Exponential
D. Hyperbolic
Answer: B. Sigmoidal (S-shaped)
Expert Rationale: The oxygen-hemoglobin dissociation curve is
sigmoidal due to cooperative binding. As the first oxygen
molecule binds, hemoglobin undergoes a conformational change
that increases the affinity for subsequent oxygen molecules,
creating the characteristic S-shape.
Question 6
The term "cooperative binding" in hemoglobin refers to:
A. Oxygen binding to plasma proteins
B. Increased oxygen affinity after the first oxygen binds
C. Hemoglobin binding to carbon dioxide
D. The exchange of chloride ions
Answer: B. Increased oxygen affinity after the first oxygen
binds
