Breathing and Exchange of Gases
Test 2

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following is NOT a factor affecting oxygen dissociation from hemoglobin?

pCO₂
pH
Enzyme concentration
Temperature
3

Oxygen dissociation from hemoglobin is influenced by pCO₂, pH, and temperature, but not by enzyme concentration.

Which of the following best describes the role of carbonic anhydrase in respiration?

Converts CO₂ into bicarbonate ions
Facilitates oxygen transport
Regulates lung volume
Enhances diffusion of gases
1

Carbonic anhydrase is an enzyme that catalyzes the conversion of CO₂ and water into carbonic acid, which dissociates into bicarbonate ions and H⁺.

Which of the following correctly describes the role of the diaphragm during inspiration?

Contracts and moves downward
Relaxes and moves upward
Expands and thickens
Remains stationary
1

During inspiration, the diaphragm contracts and moves downward, increasing thoracic volume and reducing pressure, allowing air to enter the lungs.

Which part of the brain controls the voluntary regulation of respiration?

Cerebrum
Medulla oblongata
Pons
Hypothalamus
1

The cerebrum controls voluntary regulation of respiration, while the medulla oblongata and pons regulate involuntary breathing.

Which of the following statements regarding oxygen transport is correct?

Oxygen is mainly transported in the form of bicarbonate ions.
Oxygen binds reversibly with hemoglobin to form oxyhemoglobin.
All oxygen in the blood is dissolved in plasma.
Oxygen dissociation from hemoglobin is independent of pCO₂ levels.
2

Oxygen binds reversibly with hemoglobin to form oxyhemoglobin, which facilitates oxygen transport in the blood.

Which of the following statements regarding carbon dioxide transport is incorrect?

Carbon dioxide is mainly transported as bicarbonate ions.
A small amount of CO₂ binds to hemoglobin to form carbamino-hemoglobin.
Carbonic anhydrase is present in red blood cells and facilitates CO₂ transport.
The majority of carbon dioxide is transported dissolved in plasma.
4

Most carbon dioxide is transported as bicarbonate ions, not dissolved in plasma. Therefore, statement 4 is incorrect.

Which of the following statements about respiratory volumes is correct?

Tidal volume is the volume of air exchanged during forced breathing.
Vital capacity includes tidal volume, inspiratory reserve volume, and residual volume.
Expiratory reserve volume is the additional air exhaled after a normal expiration.
Inspiratory capacity equals expiratory reserve volume plus tidal volume.
3

Expiratory reserve volume refers to the additional air that can be exhaled after a normal expiration, making statement 3 correct.

Which of the following statements about respiratory control is incorrect?

The medulla oblongata contains the respiratory rhythm center.
The pneumotaxic center controls the depth of inspiration.
Chemoreceptors detect changes in CO₂ and O₂ levels in the blood.
Respiratory rate is independent of blood pH.
4

Respiratory rate is influenced by blood pH, as an increase in CO₂ leads to a drop in pH, stimulating respiration. Therefore, statement 4 is incorrect.

Which of the following factors decreases the affinity of hemoglobin for oxygen?

Low pCO₂
Low H⁺ concentration
High temperature
Both 2 and 3
3

High temperature reduces hemoglobin’s affinity for oxygen, promoting oxygen release at tissues.

What is the function of the pneumotaxic center in respiration?

Initiates breathing movements
Enhances oxygen transport
Regulates the duration of inspiration
Increases alveolar surface area
3

The pneumotaxic center in the pons regulates respiration by controlling the duration of inspiration.

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