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Biology – Zoology

Breathing and Exchange of Gases

Breathing and Exchange of Gases

Action PlanNotesQuestionsMock-Test
Study Action Plan (Sorted by Difficulty)
Oxygen Transport and Dissociation Curve
Accuracy: 50%
Total Attempted24
Total Correct12
Total Incorrect12
Difficulty Level:
Medium
Carbon Dioxide Transport and Carbonic Anhydrase
Accuracy: 55%
Total Attempted56
Total Correct31
Total Incorrect25
Difficulty Level:
Medium
Respiratory Volumes and Capacities
Accuracy: 60%
Total Attempted30
Total Correct18
Total Incorrect12
Difficulty Level:
Medium
Regulation of Respiration
Accuracy: 62%
Total Attempted13
Total Correct8
Total Incorrect5
Difficulty Level:
Medium
Breathing Rate and Pulmonary Function Testing
Accuracy: 65%
Total Attempted17
Total Correct11
Total Incorrect6
Difficulty Level:
Medium
Transport of Oxygen and Carbon Dioxide
Accuracy: 67%
Total Attempted30
Total Correct20
Total Incorrect10
Difficulty Level:
Medium
Steps of Respiration
Accuracy: 71%
Total Attempted24
Total Correct17
Total Incorrect7
Difficulty Level:
Medium
Partial Pressure Gradients in Gas Exchange
Accuracy: 72%
Total Attempted18
Total Correct13
Total Incorrect5
Difficulty Level:
Medium
Disorders of the Respiratory System
Accuracy: 76%
Total Attempted17
Total Correct13
Total Incorrect4
Difficulty Level:
Low
Exchange of Gases
Accuracy: 77%
Total Attempted57
Total Correct44
Total Incorrect13
Difficulty Level:
Low
Mechanism of Breathing
Accuracy: 80%
Total Attempted35
Total Correct28
Total Incorrect7
Difficulty Level:
Low
Respiratory Organs in Animals
Accuracy: 85%
Total Attempted41
Total Correct35
Total Incorrect6
Difficulty Level:
Low
Human Respiratory System
Accuracy: 94%
Total Attempted33
Total Correct31
Total Incorrect2
Difficulty Level:
Low
Conducting and Respiratory Parts
Accuracy: 100%
Total Attempted12
Total Correct12
Total Incorrect0
Difficulty Level:
Low
Diffusion Membrane and Alveolar Exchange
Accuracy: 100%
Total Attempted12
Total Correct12
Total Incorrect0
Difficulty Level:
Low
High Altitude and Hypoxia Concepts
Accuracy: 100%
Total Attempted1
Total Correct1
Total Incorrect0
Difficulty Level:
Low

Learning Objectives

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Learning Objectives

  • Define and explain the significance of vital capacity.
  • Describe the volume of air remaining in the lungs after normal breathing.
  • Explain why diffusion of gases occurs in the alveolar region only.
  • Identify and explain the major transport mechanisms for CO₂.
  • Compare the partial pressures of pO₂ and pCO₂ in atmospheric air and alveolar air.
  • Describe the process of inspiration under normal conditions.
  • Explain how respiration is regulated.
  • Discuss the effect of pCO₂ on oxygen transport.
  • Analyze the respiratory process in response to altitude changes, such as going up a hill.
  • Identify the site of gaseous exchange in insects.
  • Define the oxygen dissociation curve and discuss reasons for its sigmoidal pattern.
  • Distinguish between inspiratory reserve volume (IRV) and expiratory reserve volume (ERV).
  • Compare inspiratory capacity and expiratory capacity.
  • Define vital capacity and total lung capacity.
  • Define tidal volume and calculate its approximate value for a healthy human in an hour.

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Revision Notes & Summary

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Chapter 14: Breathing and Exchange of Gases

14.1 Respiratory Organs

  • Oxygen (O₂) is utilized by organisms to break down molecules for energy.
  • Carbon dioxide (CO₂) is released during catabolic reactions.
  • Breathing is the exchange of O₂ from the atmosphere with CO₂ produced by cells.
  • Mechanisms of breathing vary among animals:
    • Lower invertebrates: Simple diffusion over body surface.
    • Earthworms: Use moist cuticle.
    • Insects: Tracheal tubes for air transport.
    • Aquatic arthropods/molluscs: Gills for gas exchange.
    • Terrestrial forms: Lungs for gas exchange.
    • Amphibians: Can also respire through moist skin.

14.2 Mechanism of Breathing

  • Breathing involves:
    • Inspiration: Drawing in air.
    • Expiration: Releasing air.
  • Pressure gradients are created for air movement:
    • Inspiration occurs when intra-pulmonary pressure < atmospheric pressure.
    • Expiration occurs when intra-pulmonary pressure > atmospheric pressure.
  • Muscles involved:
    • Diaphragm: Increases thoracic volume.
    • External intercostal muscles: Lift ribs.

14.3 Exchange of Gases

  • Alveoli are primary sites for gas exchange.
  • Gases diffuse based on pressure/concentration gradients.
  • Factors affecting diffusion:
    • Solubility of gases.
    • Thickness of membranes.
  • Partial Pressure:
    • pO₂ for oxygen.
    • pCO₂ for carbon dioxide.

Table 14.1: Partial Pressures (in mm Hg) of Oxygen and Carbon Dioxide

Respiratory GasAtmospheric AirAlveoliBlood (Deoxygenated)Blood (Oxygenated)Tissues
O₂159104409540
CO₂0.340454045

14.4 Transport of Gases

  • Oxygen is mainly transported as oxyhaemoglobin.
  • CO₂ is transported as:
    • 70% as bicarbonate (HCO₃) with carbonic anhydrase.
    • 20-25% as carbamino-haemoglobin.

14.5 Regulation of Respiration

  • Regulated by the respiratory centre in the medulla of the brain.
  • Pneumotaxic centre in the pons can modify respiratory functions.
  • Chemosensitive area responds to CO₂ and H+ levels.

14.6 Disorders of Respiratory System

  • Asthma: Difficulty in breathing due to bronchi inflammation.
  • Emphysema: Damage to alveolar walls, reducing respiratory surface, often caused by smoking.

Important Diagrams

  • Figure 14.1: Diagrammatic view of the human respiratory system.
  • Figure 14.3: Gas exchange process in the respiratory and circulatory systems.
  • Figure 14.4: Structure of an alveolar cavity highlighting gas exchange barriers.
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Practice Test – MCQs, True/False

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Multiple Choice Questions

A.

Partial pressure of oxygen (pO2pO_2)

B.

Partial pressure of carbon dioxide (pCO2pCO_2)

C.

Hydrogen ion concentration

D.

Temperature
Correct Answer: A

Solution:

The binding of oxygen to hemoglobin is primarily influenced by the partial pressure of oxygen (pO2pO_2) in the alveoli.

Chapter Concept:

Human Respiratory System

A.

Alveolar squamous epithelium, capillary endothelium, and basement substance

B.

Bronchial epithelium, capillary endothelium, and pleural membrane

C.

Tracheal epithelium, alveolar epithelium, and diaphragm

D.

Nasal epithelium, pharyngeal lining, and laryngeal cartilage
Correct Answer: A

Solution:

The thin diffusion membrane in the alveoli is formed by the alveolar squamous epithelium, capillary endothelium, and the basement substance, which facilitates efficient gas exchange.

Chapter Concept:

Diffusion Membrane and Alveolar Exchange

A.

It converts carbon dioxide directly into oxygen.

B.

It catalyzes the conversion of carbon dioxide and water into carbonic acid.

C.

It binds carbon dioxide to hemoglobin.

D.

It increases the solubility of carbon dioxide in plasma.
Correct Answer: B

Solution:

Carbonic anhydrase catalyzes the conversion of carbon dioxide and water into carbonic acid (H2CO3H_2CO_3), which then dissociates into bicarbonate ions (HCO3−HCO_3^-) and hydrogen ions (H+H^+), facilitating the transport of carbon dioxide in the blood.

Chapter Concept:

Exchange of Gases

A.

Inspiration occurs when the intra-pulmonary pressure is greater than the atmospheric pressure.

B.

Inspiration occurs when the intra-pulmonary pressure is less than the atmospheric pressure.

C.

Inspiration occurs when the diaphragm relaxes and the thoracic volume decreases.

D.

Inspiration occurs when the external intercostal muscles contract, decreasing thoracic volume.
Correct Answer: B

Solution:

Inspiration occurs when the intra-pulmonary pressure is less than the atmospheric pressure, which allows air to flow into the lungs due to the pressure gradient. This is facilitated by the contraction of the diaphragm and external intercostal muscles, increasing the thoracic volume.

Chapter Concept:

Breathing Rate and Pulmonary Function Testing

A.

Residual Volume (RV)

B.

Tidal Volume (TV)

C.

Functional Residual Capacity (FRC)

D.

Total Lung Capacity (TLC)
Correct Answer: B

Solution:

A spirometer can directly measure Tidal Volume (TV), which is the volume of air inspired or expired during a normal respiration. Residual Volume (RV) and Functional Residual Capacity (FRC) cannot be directly measured using a spirometer as they involve air remaining in the lungs after expiration.

Chapter Concept:

Breathing Rate and Pulmonary Function Testing

A.

It directly binds to carbon dioxide.

B.

It converts carbon dioxide into bicarbonate ions.

C.

It transports carbon dioxide as carbamino-haemoglobin.

D.

It increases the solubility of carbon dioxide in plasma.
Correct Answer: B

Solution:

Carbonic anhydrase catalyzes the conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions, facilitating its transport in the blood.

Chapter Concept:

Carbon Dioxide Transport and Carbonic Anhydrase

A.

Shifts the curve to the left

B.

Shifts the curve to the right

C.

Does not affect the curve

D.

Makes the curve steeper
Correct Answer: B

Solution:

An increase in temperature causes a rightward shift in the oxygen dissociation curve, reducing hemoglobin's affinity for oxygen and promoting oxygen release to tissues.

Chapter Concept:

Oxygen Transport and Dissociation Curve

A.

It shows the relationship between hemoglobin saturation and pO2pO_2.

B.

It indicates the rate of carbon dioxide transport in the blood.

C.

It demonstrates the effect of temperature on breathing rate.

D.

It explains the mechanism of gas exchange in alveoli.
Correct Answer: A

Solution:

The oxygen dissociation curve is a graphical representation of the relationship between the percentage saturation of hemoglobin with oxygen and the partial pressure of oxygen (pO2pO_2).

Chapter Concept:

Human Respiratory System

A.

Increased lung elasticity due to fibrous tissue proliferation.

B.

Decreased lung capacity due to inflammation and fibrosis.

C.

Enhanced oxygen transport due to increased blood flow.

D.

Reduced alveolar oxygen exchange efficiency due to bronchiole dilation.
Correct Answer: B

Solution:

Occupational respiratory disorders often result in inflammation and fibrosis due to prolonged dust exposure, which decreases lung capacity and impairs respiratory function.

Chapter Concept:

Disorders of the Respiratory System

A.

Increased tidal volume

B.

Decreased breathing rate

C.

Reduced hemoglobin affinity for oxygen

D.

Increased production of erythrocytes
Correct Answer: D

Solution:

At high altitudes, the body compensates for reduced oxygen availability by increasing the production of erythrocytes (red blood cells) to enhance oxygen transport capacity.

Chapter Concept:

High Altitude and Hypoxia Concepts

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Breathing and Exchange of Gases

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True or False

Correct Answer: True

Solution:

The partial pressure of oxygen (pO2pO_2) in the alveoli is 104 mm Hg, while in deoxygenated blood, it is 40 mm Hg, creating a gradient for oxygen to diffuse from the alveoli into the blood.

Chapter Concept :

Partial Pressure Gradients in Gas Exchange

Correct Answer: True

Solution:

Oxygen is transported mainly as oxyhaemoglobin. Haemoglobin, a red-colored iron-containing pigment in RBCs, binds with oxygen in a reversible manner to form oxyhaemoglobin.

Chapter Concept :

Steps of Respiration

Correct Answer: False

Solution:

Oxyhaemoglobin formation is favored in the alveoli where pO2pO_2 is high and pCO2pCO_2 is low, not in the tissues.

Chapter Concept :

Transport of Oxygen and Carbon Dioxide

Correct Answer: True

Solution:

Tidal volume (TV) is defined as the volume of air inspired or expired during a normal respiration, approximately 500 mL.

Chapter Concept :

Respiratory Volumes and Capacities

Correct Answer: True

Solution:

In tissues, low partial pressure of oxygen (pO2pO_2), high partial pressure of carbon dioxide (pCO2pCO_2), high concentration of hydrogen ions (H+H^+), and increased temperature create an environment that promotes the release of oxygen from oxyhaemoglobin.

Chapter Concept :

Oxygen Transport and Dissociation Curve

Correct Answer: True

Solution:

Inspiration is initiated by the contraction of the diaphragm and external intercostal muscles, increasing thoracic volume and decreasing intra-pulmonary pressure below atmospheric pressure, allowing air to enter the lungs.

Chapter Concept :

Mechanism of Breathing

Correct Answer: True

Solution:

The partial pressure of oxygen (pO2pO_2) in the alveoli is 104 mm Hg, which is higher than the pO2pO_2 of 40 mm Hg in deoxygenated blood from the pulmonary artery.

Chapter Concept :

Exchange of Gases

Correct Answer: True

Solution:

Inspiration is initiated by the contraction of the diaphragm and intercostal muscles, which increases the thoracic cavity volume, creating a pressure gradient that allows air to enter the lungs.

Chapter Concept :

Human Respiratory System

Correct Answer: True

Solution:

Residual Volume (RV) refers to the volume of air that remains in the lungs even after a person exhales forcefully, and it typically averages between 1100 mL to 1200 mL.

Chapter Concept :

Respiratory Volumes and Capacities

Correct Answer: True

Solution:

Emphysema is characterized by the destruction of alveolar walls, which reduces the surface area available for gas exchange, impairing respiratory efficiency.

Chapter Concept :

Disorders of the Respiratory System

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