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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.

Vital Capacity (VC)

B.

Total Lung Capacity (TLC)

C.

Inspiratory Capacity (IC)

D.

Functional Residual Capacity (FRC)
Correct Answer: C

Solution:

Inspiratory Capacity (IC) is the total volume of air a person can inspire after a normal expiration, which includes tidal volume and inspiratory reserve volume (TV+IRV).

Chapter Concept:

Respiratory Volumes and Capacities

A.

Pulmonary ventilation

B.

Alveolar gas diffusion

C.

Blood transport

D.

Cellular utilization of O2O_2
Correct Answer: B

Solution:

Alveolar gas diffusion is the step where O2O_2 and CO2CO_2 are exchanged between the alveoli and the blood due to pressure gradients.

Chapter Concept:

Steps of Respiration

A.

It contracts and moves upwards, decreasing thoracic volume.

B.

It contracts and moves downwards, increasing thoracic volume.

C.

It relaxes and moves upwards, increasing thoracic volume.

D.

It relaxes and moves downwards, decreasing thoracic volume.
Correct Answer: B

Solution:

During inspiration, the diaphragm contracts and moves downwards, increasing the volume of the thoracic cavity, which decreases the intra-pulmonary pressure and allows air to flow into the lungs.

Chapter Concept:

Mechanism of Breathing

A.

Alveoli

B.

Terminal bronchioles

C.

Conducting part from nostrils to terminal bronchioles

D.

Diaphragm
Correct Answer: C

Solution:

The conducting part of the respiratory system, which extends from the nostrils to the terminal bronchioles, is responsible for transporting atmospheric air to the alveoli, filtering out foreign particles, humidifying the air, and adjusting its temperature.

Chapter Concept:

Conducting and Respiratory Parts

A.

Epiglottis

B.

Larynx

C.

Bronchi

D.

Diaphragm
Correct Answer: A

Solution:

The epiglottis is a flap of tissue that covers the glottis during swallowing, preventing food from entering the trachea.

Chapter Concept:

Human Respiratory System

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.

Contraction of diaphragm and intercostal muscles

B.

Relaxation of diaphragm

C.

Contraction of abdominal muscles

D.

Expansion of alveoli
Correct Answer: A

Solution:

Inspiration is initiated by the contraction of the diaphragm and external intercostal muscles, increasing thoracic volume and decreasing intra-pulmonary pressure.

Chapter Concept:

Human Respiratory System

A.

Nasal cavity

B.

Trachea

C.

Alveoli

D.

Bronchi
Correct Answer: C

Solution:

The alveoli and their ducts form the respiratory or exchange part of the respiratory system where the actual diffusion of O2O_2 and CO2CO_2 occurs.

Chapter Concept:

Conducting and Respiratory Parts

A.

To transport oxygen

B.

To reduce friction on the lung surface

C.

To facilitate sound production

D.

To increase the surface area for gas exchange
Correct Answer: B

Solution:

The pleural fluid is located between the two layers of the pleura surrounding each lung. Its primary function is to reduce friction on the lung surface during breathing movements.

Chapter Concept:

Conducting and Respiratory Parts

A.

It reduces friction on the lung surface during breathing.

B.

It facilitates the exchange of gases in the alveoli.

C.

It helps in the transport of oxygen in the blood.

D.

It acts as a barrier to pathogens entering the lungs.
Correct Answer: A

Solution:

The pleural fluid is located between the pleural membranes and reduces friction on the lung surface during breathing.

Chapter Concept:

Human Respiratory System

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Breathing and Exchange of Gases

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True or False

Correct Answer: True

Solution:

Asthma involves inflammation of the bronchi and bronchioles, leading to wheezing and difficulty in breathing.

Chapter Concept :

Disorders of the Respiratory System

Correct Answer: False

Solution:

The conducting part of the respiratory system extends from the external nostrils to the terminal bronchioles, while the alveoli and their ducts form the respiratory or exchange part.

Chapter Concept :

Conducting and Respiratory Parts

Correct Answer: True

Solution:

Approximately 70% of carbon dioxide is transported as bicarbonate ions in the blood.

Chapter Concept :

Transport of Oxygen and Carbon Dioxide

Correct Answer: False

Solution:

Oxygen is primarily transported by binding to hemoglobin in red blood cells, with only a small percentage dissolved in plasma.

Chapter Concept :

Human Respiratory System

Correct Answer: True

Solution:

Insects have a specialized respiratory system consisting of tracheal tubes that directly transport atmospheric air to the tissues.

Chapter Concept :

Respiratory Organs in Animals

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:

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:

Oxygen binds with haemoglobin in a reversible manner to form oxyhaemoglobin, which is the primary mode of oxygen transport in the blood.

Chapter Concept :

Transport of Oxygen and Carbon Dioxide

Correct Answer: False

Solution:

The regulation of respiratory rhythm is primarily controlled by the respiratory rhythm center located in the medulla region of the brain, while the pneumotaxic center in the pons can moderate its function.

Chapter Concept :

Regulation of Respiration

Correct Answer: False

Solution:

The majority of carbon dioxide (about 70%) in the blood is transported as bicarbonate ions (HCO3−HCO_3^-), while only 20-25% is transported as carbamino-haemoglobin.

Chapter Concept :

Carbon Dioxide Transport and Carbonic Anhydrase

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