Breathing and Exchange of Gases

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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.

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 Gas	Atmospheric Air	Alveoli	Blood (Deoxygenated)	Blood (Oxygenated)	Tissues
O₂	159	104	40	95	40
CO₂	0.3	40	45	40	45

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.

Exam Tips & Common Mistakes

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Common Mistakes and Exam Tips

Common Pitfalls

Misunderstanding Gas Exchange: Students often confuse the sites of gas exchange. Remember that gas exchange primarily occurs in the alveoli, not in other parts of the respiratory system.
Confusing Respiratory Volumes: Be clear about different respiratory volumes and capacities. For example, Residual Volume (RV) is the air remaining after forced expiration, while Vital Capacity (VC) is the maximum air that can be exhaled after a maximum inhalation.
Ignoring Partial Pressures: Students may overlook the significance of partial pressures (pO₂ and pCO₂) in gas exchange. Understand that these pressures drive the diffusion of gases.
Overlooking Regulation Mechanisms: The regulation of respiration is often misunderstood. Focus on the role of the medulla and pons in controlling the respiratory rhythm.

Tips for Exam Preparation

Diagrams and Figures: Familiarize yourself with diagrams such as the oxygen dissociation curve and the structure of the respiratory system. Being able to label these can help in exams.
Definitions and Functions: Make sure you can define key terms like Vital Capacity, Tidal Volume, and explain their significance in respiratory physiology.
Practice with Questions: Use practice questions to test your understanding of concepts like the mechanisms of breathing and the transport of gases in the blood.
Understand Disorders: Be aware of common respiratory disorders like asthma and emphysema, including their causes and effects on the respiratory system.

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Practice Test – MCQs, True/False

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Multiple Choice Questions

Linear

Sigmoidal

Exponential

Parabolic

Correct Answer: B

Solution:

The oxygen dissociation curve is sigmoidal in shape, indicating how hemoglobin's oxygen binding affinity changes with different partial pressures of oxygen.

Increased diffusion of both O₂ and CO₂.

Decreased diffusion of both O₂ and CO₂.

Increased diffusion of O₂ but decreased diffusion of CO₂.

Decreased diffusion of O₂ but increased diffusion of CO₂.

Correct Answer: B

Solution:

The diffusion of gases is inversely proportional to the thickness of the membrane. An increase in membrane thickness would decrease the diffusion rate of both O₂ and CO₂.

Decrease in red blood cell count

Decrease in hemoglobin affinity for oxygen

Increase in tidal volume

Decrease in heart rate

Correct Answer: C

Solution:

At high altitudes, the body compensates for lower oxygen availability by increasing tidal volume, which enhances oxygen uptake.

Dissolved in plasma

As bicarbonate ions

Bound to haemoglobin

As carbonic acid

Correct Answer: B

Solution:

About 70% of CO₂ is transported as bicarbonate ions in the blood.

High

pCO_2

Low temperature

High

H^+

concentration

High temperature

Correct Answer: B

Solution:

Low temperature in the lungs increases the affinity of hemoglobin for oxygen, facilitating oxygen binding. High

pCO_2

and high

H^+

concentration would decrease affinity.

159 mm Hg

104 mm Hg

95 mm Hg

40 mm Hg

Correct Answer: B

Solution:

The partial pressure of oxygen (pO₂) in the alveoli is approximately 104 mm Hg, as indicated in the provided data.

45 mm Hg

40 mm Hg

50 mm Hg

35 mm Hg

Correct Answer: A

Solution:

The

pCO_2

in systemic veins is typically higher than in the alveoli due to the accumulation of carbon dioxide from tissue metabolism. It is around 45 mm Hg.

Increases oxygen binding to hemoglobin

Decreases oxygen binding to hemoglobin

No effect on oxygen binding

Converts oxygen to carbon dioxide

Correct Answer: B

Solution:

High partial pressure of carbon dioxide (

pCO_2

) decreases oxygen binding to hemoglobin.

Transports oxygen only

Transports carbon dioxide only

Transports both oxygen and carbon dioxide

Transports nitrogen

Correct Answer: C

Solution:

Haemoglobin in red blood cells transports both oxygen and carbon dioxide.

The variant has a higher affinity for oxygen.

The variant has a lower affinity for oxygen.

The variant's affinity for oxygen is unchanged.

The variant cannot bind oxygen.

Correct Answer: A

Solution:

A leftward shift in the oxygen dissociation curve indicates a higher affinity for oxygen, meaning the hemoglobin holds onto oxygen more tightly.

Decrease in thoracic volume and increase in pulmonary pressure

Increase in thoracic volume and decrease in pulmonary pressure

Decrease in thoracic volume and decrease in pulmonary pressure

Increase in thoracic volume and increase in pulmonary pressure

Correct Answer: B

Solution:

During inspiration, the thoracic volume increases, leading to a decrease in pulmonary pressure, which allows air to flow into the lungs.

Partial pressure of oxygen

Partial pressure of carbon dioxide

Temperature

Atmospheric pressure

Correct Answer: D

Solution:

Atmospheric pressure is not a direct factor affecting the binding of oxygen to hemoglobin.

The curve shifts to the left.

The curve shifts to the right.

The curve remains unchanged.

The curve becomes a straight line.

Correct Answer: B

Solution:

During heavy exercise, the curve shifts to the right due to increased

pCO_2

, increased temperature, and increased

H^+

concentration, facilitating oxygen release to tissues.

Bronchi

Trachea

Alveoli

Bronchioles

Correct Answer: C

Solution:

Alveoli are the primary sites of exchange of gases in the human respiratory system.

Increased oxygen transport due to enhanced CO₂ binding

Decreased oxygen transport due to competitive binding

No effect on oxygen transport

Increased oxygen transport due to higher affinity for O₂

Correct Answer: B

Solution:

A higher affinity for CO₂ would result in more CO₂ binding to hemoglobin, reducing the available sites for O₂ binding, thereby decreasing oxygen transport.

Solubility of the gases

Thickness of the diffusion membrane

Color of the blood

Pressure gradient

Correct Answer: C

Solution:

The color of the blood does not affect the rate of diffusion of gases. Factors such as solubility, thickness of the membrane, and pressure gradient do.

Bronchi

Trachea

Alveoli

Larynx

Correct Answer: C

Solution:

The alveoli are the primary sites of gas exchange in the human respiratory system.

Increased heart rate to compensate for reduced oxygen delivery

Decreased breathing rate due to reduced oxygen demand

Increased production of carbonic acid in the blood

Decreased affinity of hemoglobin for oxygen

Correct Answer: A

Solution:

A decrease in

pO_2

in the alveoli would likely lead to hypoxemia, prompting the body to increase the heart rate to deliver more oxygen to tissues.

Tidal Volume (TV)

Inspiratory Reserve Volume (IRV)

Expiratory Reserve Volume (ERV)

Inspiratory Capacity (IC)

Correct Answer: C

Solution:

Emphysema primarily affects the ability to expel air from the lungs, which would reduce the Expiratory Reserve Volume (ERV).

The diaphragm contracts and moves upwards, decreasing the thoracic volume.

The diaphragm contracts and moves downwards, increasing the thoracic volume.

The diaphragm relaxes and moves upwards, increasing the thoracic volume.

The diaphragm relaxes and moves downwards, decreasing the thoracic volume.

Correct Answer: B

Solution:

During inspiration, the diaphragm contracts and moves downwards, increasing the thoracic volume and decreasing the intrapulmonary pressure, which allows air to flow into the lungs.

High pO₂, low pCO₂, low temperature

Low pO₂, high pCO₂, high temperature

High pO₂, high pCO₂, low temperature

Low pO₂, low pCO₂, high temperature

Correct Answer: B

Solution:

In the tissues, the conditions of low pO₂, high pCO₂, and high temperature favor the dissociation of oxygen from oxyhaemoglobin, facilitating oxygen delivery to the tissues.

Tidal Volume (TV) and Inspiratory Reserve Volume (IRV)

Expiratory Reserve Volume (ERV) and Residual Volume (RV)

Inspiratory Capacity (IC) and Expiratory Reserve Volume (ERV)

Vital Capacity (VC) and Residual Volume (RV)

Correct Answer: B

Solution:

Functional Residual Capacity (FRC) is the volume of air remaining in the lungs after a normal expiration, which includes Expiratory Reserve Volume (ERV) and Residual Volume (RV).

The diaphragm contracts and moves downward, increasing thoracic volume.

The diaphragm relaxes and moves upward, decreasing thoracic volume.

The diaphragm contracts and moves upward, decreasing thoracic volume.

The diaphragm relaxes and moves downward, increasing thoracic volume.

Correct Answer: A

Solution:

During inspiration, the diaphragm contracts and moves downward, which increases the volume of the thoracic cavity. This decrease in pressure allows air to flow into the lungs.

The volume of air remaining in the lungs after a normal expiration

The maximum volume of air a person can breathe in after a forced expiration

The volume of air inspired or expired during a normal respiration

The total volume of air a person can inspire after a normal expiration

Correct Answer: B

Solution:

Vital capacity is the maximum volume of air a person can breathe in after a forced expiration.

Alveoli

Bronchi

Trachea

Larynx

Correct Answer: A

Solution:

Alveoli are the primary sites of gas exchange in the human respiratory system, where oxygen and carbon dioxide are exchanged between the air and blood.

Increase in vital capacity

Decrease in vital capacity

No change in vital capacity

Increase in total lung capacity

Correct Answer: B

Solution:

Vital capacity (VC) is the sum of inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV). A decrease in IRV would directly lead to a decrease in VC.

Tidal Volume (TV)

Inspiratory Reserve Volume (IRV)

Vital Capacity (VC)

Residual Volume (RV)

Correct Answer: C

Solution:

Vital Capacity (VC) is the maximum volume of air a person can breathe out after a forced inspiration. It includes the inspiratory reserve volume, tidal volume, and expiratory reserve volume.

159 mm Hg

140 mm Hg

120 mm Hg

100 mm Hg

Correct Answer: A

Solution:

The partial pressure of oxygen in atmospheric air is typically around 159 mm Hg, as given by the equation

pO_2 = 0.21 \times 760

mm Hg, where 0.21 is the fraction of oxygen in the air.

3600 mL

4600 mL

4100 mL

5100 mL

Correct Answer: B

Solution:

Vital capacity (VC) is calculated as the sum of tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). Therefore, VC = TV + IRV + ERV = 500 + 3000 + 1100 = 4600 mL.

Increased diffusion rate of both O₂ and CO₂

Decreased diffusion rate of both O₂ and CO₂

Increased diffusion rate of O₂ but decreased rate of CO₂

Decreased diffusion rate of O₂ but increased rate of CO₂

Correct Answer: B

Solution:

An increase in membrane thickness would decrease the diffusion rate of gases, as diffusion is inversely proportional to membrane thickness.

Partial pressure of oxygen

Partial pressure of carbon dioxide

Temperature

Concentration of nitrogen in the blood

Correct Answer: D

Solution:

The concentration of nitrogen in the blood does not affect the binding of oxygen to hemoglobin. The factors that do affect this binding include the partial pressures of oxygen and carbon dioxide, hydrogen ion concentration, and temperature.

It increases

It decreases

It remains the same

It fluctuates randomly

Correct Answer: B

Solution:

The partial pressure of oxygen decreases as blood moves from the alveoli to the tissues due to the diffusion of oxygen from the blood into the tissues.

Transport of nutrients

Transport of oxygen

Regulation of body temperature

Clotting of blood

Correct Answer: B

Solution:

Hemoglobin is a red colored iron-containing pigment in red blood cells that binds with oxygen to transport it throughout the body.

It dissolves oxygen in plasma.

It binds with oxygen to form oxyhemoglobin.

It converts oxygen into carbon dioxide.

It stores oxygen in muscles.

Correct Answer: B

Solution:

Hemoglobin binds with oxygen in a reversible manner to form oxyhemoglobin, facilitating oxygen transport in the blood.

Dissolved in plasma

As bicarbonate ions

Bound to haemoglobin as carbamino-haemoglobin

As carbonic acid

Correct Answer: B

Solution:

About 70% of CO₂ is transported in the blood as bicarbonate ions, which is the major form of carbon dioxide transport.

Dissolved in plasma

Bound to hemoglobin as carbaminohemoglobin

As bicarbonate ions in plasma

Directly bound to oxygen

Correct Answer: C

Solution:

Approximately 70% of carbon dioxide is transported in the blood as bicarbonate ions, making it the primary mechanism for carbon dioxide transport.

Alveoli

Trachea

Bronchi

Larynx

Correct Answer: A

Solution:

Alveoli are the primary sites of exchange of gases in humans.

The binding of the first oxygen molecule to hemoglobin increases the affinity for the next oxygen molecule.

The binding of oxygen to hemoglobin is independent of partial pressure.

The dissociation of oxygen from hemoglobin is a linear process.

The presence of carbon dioxide decreases the affinity of hemoglobin for oxygen.

Correct Answer: A

Solution:

The sigmoidal shape of the oxygen dissociation curve is due to cooperative binding, where the binding of the first oxygen molecule increases the affinity of hemoglobin for subsequent oxygen molecules.

100 mL

500 mL

1000 mL

1500 mL

Correct Answer: B

Solution:

The average tidal volume for a healthy human during normal respiration is approximately 500 mL.

Dissolved in plasma

Bound to hemoglobin

As bicarbonate ions

In white blood cells

Correct Answer: B

Solution:

About 97% of oxygen is transported by red blood cells in the form of oxyhemoglobin, while the remaining 3% is dissolved in plasma.

It increases above atmospheric pressure

It decreases below atmospheric pressure

It remains constant

It becomes equal to atmospheric pressure

Correct Answer: B

Solution:

During inspiration, the intra-pulmonary pressure decreases below atmospheric pressure, allowing air to flow into the lungs.

The rate of CO₂ diffusion would increase.

The rate of CO₂ diffusion would decrease.

The rate of CO₂ diffusion would remain unchanged.

The diffusion of CO₂ would stop completely.

Correct Answer: B

Solution:

The solubility of CO₂ is a key factor in its diffusion across the alveolar membrane. A decrease in solubility would reduce the rate of CO₂ diffusion.

The amphibian will uptake more oxygen through its lungs.

The amphibian will uptake more oxygen through its skin.

The oxygen uptake will be equal through both lungs and skin.

The amphibian will not uptake oxygen through its skin.

Correct Answer: A

Solution:

The oxygen uptake is driven by the partial pressure gradient. Since the

pO_2

in the lung environment is higher, the amphibian will uptake more oxygen through its lungs.

Tidal Volume

Residual Volume

Expiratory Reserve Volume

Functional Residual Capacity

Correct Answer: D

Solution:

Functional Residual Capacity (FRC) is the volume of air remaining in the lungs after a normal expiration.

159 mm Hg

104 mm Hg

95 mm Hg

40 mm Hg

Correct Answer: B

Solution:

The partial pressure of oxygen in the alveolar air is 104 mm Hg.

Increase the rate of diffusion for both O₂ and CO₂

Decrease the rate of diffusion for both O₂ and CO₂

Increase the rate of diffusion for O₂ but decrease for CO₂

No effect on the diffusion of gases

Correct Answer: B

Solution:

The rate of diffusion of gases is inversely proportional to the thickness of the membrane. A 30% increase in the thickness of the alveolar membrane would decrease the rate of diffusion for both O₂ and CO₂.

Increased binding of O₂ to hemoglobin.

Decreased binding of O₂ to hemoglobin.

No change in O₂ binding to hemoglobin.

Increased CO₂ binding to hemoglobin.

Correct Answer: B

Solution:

At high altitudes, the

pO_2

in the alveoli is reduced, leading to decreased binding of O₂ to hemoglobin as the partial pressure gradient is less favorable.

Approximately 7%

Approximately 20-25%

Approximately 70%

Approximately 97%

Correct Answer: C

Solution:

Approximately 70% of carbon dioxide is transported in the blood as bicarbonate ions, which is the major form of CO₂ transport.

Dissolved in plasma

As bicarbonate ions

Bound to hemoglobin

As carbonic acid

Correct Answer: B

Solution:

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

Mostly dissolved in plasma

Bound to hemoglobin as carbamino-haemoglobin

Carried as bicarbonate ions

Transported as carbonic acid

Correct Answer: C

Solution:

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

Dissolved in plasma

Bound to hemoglobin as carbamino-hemoglobin

As bicarbonate ions

As carbonic acid

Correct Answer: C

Solution:

The majority of carbon dioxide is transported in the blood as bicarbonate ions (about 70%). This conversion occurs in the red blood cells and is facilitated by the enzyme carbonic anhydrase.

It relaxes and moves upwards.

It contracts and moves downwards.

It remains stationary.

It contracts and moves upwards.

Correct Answer: B

Solution:

During inspiration, the diaphragm contracts and moves downwards, increasing the thoracic volume.

Increased binding of CO₂ to hemoglobin

Decreased binding of O₂ to hemoglobin

Increased rate of oxygen diffusion into the blood

No change in the oxygen dissociation curve

Correct Answer: B

Solution:

An increase in alveolar pCO₂ would lead to a decrease in the binding of O₂ to hemoglobin due to the Bohr effect, where high CO₂ levels facilitate the release of O₂ from hemoglobin.

High pO₂, low pCO₂, low temperature

Low pO₂, high pCO₂, high temperature

High pO₂, high pCO₂, low temperature

Low pO₂, low pCO₂, high temperature

Correct Answer: B

Solution:

In tissues, the conditions that favor the release of oxygen from oxyhemoglobin include low pO₂, high pCO₂, and high temperature. These conditions promote the dissociation of oxygen from hemoglobin, facilitating oxygen delivery to the tissues.

The diaphragm contracts and moves downward, increasing thoracic volume.

The diaphragm relaxes and moves upward, decreasing thoracic volume.

The diaphragm contracts and moves upward, decreasing thoracic volume.

The diaphragm relaxes and moves downward, increasing thoracic volume.

Correct Answer: B

Solution:

During expiration, the diaphragm relaxes and moves upward, which decreases the thoracic volume and increases the intra-pulmonary pressure, leading to the expulsion of air from the lungs.

70%

97%

50%

30%

Correct Answer: B

Solution:

About 97% of oxygen is transported by red blood cells in the blood.

Decrease in red blood cell production

Increase in red blood cell production

Decrease in hemoglobin affinity for oxygen

Increase in hemoglobin affinity for carbon dioxide

Correct Answer: B

Solution:

At high altitudes, the body adapts by increasing red blood cell production to enhance oxygen transport capacity in response to reduced pO₂.

Branchial respiration

Pulmonary respiration

Cutaneous respiration

Tracheal respiration

Correct Answer: A

Solution:

Branchial respiration involves the use of gills, which are specialized structures for gas exchange in aquatic organisms.

Linear

Exponential

Sigmoidal

Parabolic

Correct Answer: C

Solution:

The oxygen dissociation curve is sigmoidal in shape, which reflects the cooperative binding of oxygen to hemoglobin.

Tidal Volume

Inspiratory Reserve Volume

Expiratory Reserve Volume

Functional Residual Capacity

Correct Answer: D

Solution:

Functional Residual Capacity (FRC) is the volume of air remaining in the lungs after a normal expiration.

Inspiratory Capacity

Expiratory Reserve Volume

Functional Residual Capacity

Residual Volume

Correct Answer: C

Solution:

Functional Residual Capacity (FRC) is the volume of air that remains in the lungs after a normal expiration.

The alveolar walls are impermeable to gases.

The alveoli have a large surface area and thin walls, facilitating diffusion.

The alveolar region is the only part of the respiratory system that contains blood vessels.

The alveolar region has a higher concentration of carbon dioxide than oxygen.

Correct Answer: B

Solution:

The alveoli provide a large surface area and have thin walls, which are ideal conditions for the diffusion of gases such as oxygen and carbon dioxide.

It relaxes and moves upward

It contracts and moves downward

It contracts and moves upward

It relaxes and moves downward

Correct Answer: B

Solution:

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

Alveolar air has higher pO₂ and higher pCO₂ than atmospheric air.

Alveolar air has lower pO₂ and lower pCO₂ than atmospheric air.

Alveolar air has higher pO₂ and lower pCO₂ than atmospheric air.

Alveolar air has lower pO₂ and higher pCO₂ than atmospheric air.

Correct Answer: D

Solution:

Alveolar air has a lower partial pressure of oxygen (pO₂) and a higher partial pressure of carbon dioxide (pCO₂) compared to atmospheric air due to the exchange of gases that occurs in the alveoli.

High pO₂, low pCO₂, low H⁺ concentration, lower temperature

Low pO₂, high pCO₂, high H⁺ concentration, higher temperature

High pO₂, high pCO₂, high H⁺ concentration, higher temperature

Low pO₂, low pCO₂, low H⁺ concentration, lower temperature

Correct Answer: A

Solution:

The formation of oxyhemoglobin is favored in the alveoli where the conditions are high pO₂, low pCO₂, low H⁺ concentration, and lower temperature, as these conditions enhance the binding of oxygen to hemoglobin.

Earthworm

Fish

Insect

Frog

Correct Answer: C

Solution:

Insects have a network of tracheal tubes that transport atmospheric air directly to their tissues.

True or False

Correct Answer: True

Solution:

The alveoli are the primary sites of gas exchange in humans, where oxygen and carbon dioxide are exchanged between the air and the blood.

Correct Answer: True

Solution:

The alveolar region is specifically adapted for the diffusion of gases, making it the primary site for gaseous exchange.

Correct Answer: True

Solution:

Systems biology focuses on understanding the emergent properties that result from the interactions among various components, such as molecules, cells, and tissues, within a biological system.

Correct Answer: False

Solution:

Insects use a network of tracheal tubes to transport atmospheric air within the body, not their moist skin.

Correct Answer: False

Solution:

Breathing is the process of exchanging oxygen from the atmosphere with carbon dioxide produced by the cells, while respiration includes the biochemical processes that occur within cells.

Correct Answer: False

Solution:

The oxygen dissociation curve is sigmoidal, not linear, indicating that the binding of oxygen to hemoglobin is affected by factors such as partial pressure of oxygen, carbon dioxide, hydrogen ion concentration, and temperature.

Correct Answer: True

Solution:

Amphibians, such as frogs, can respire through their lungs and also through their moist skin, a process known as cutaneous respiration.

Correct Answer: True

Solution:

The excerpt explains that both approaches are necessary to understand biological processes, as systems biology shows that living phenomena are emergent properties due to interactions among components.

Correct Answer: False

Solution:

The reductionist approach focuses on breaking down life forms into their simplest components, while the organismic approach considers the whole organism. Neither approach alone reveals the full truth about biological processes.

Correct Answer: False

Solution:

Residual volume is the volume of air remaining in the lungs after a forcible expiration, not a normal expiration.

Correct Answer: False

Solution:

The volume of air remaining in the lungs after a normal expiration is called the Functional Residual Capacity, not the Vital Capacity.

Correct Answer: True

Solution:

The reductionist approach emphasizes the use of physico-chemical concepts and techniques, often employing surviving tissue models or cell-free systems.

Correct Answer: False

Solution:

About 97% of oxygen is transported by red blood cells (RBCs) in the blood, not primarily dissolved in plasma.

Correct Answer: True

Solution:

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

Correct Answer: False

Solution:

The excerpt suggests that neither a purely organismic approach nor a purely reductionistic molecular approach alone is sufficient to reveal the truth about biological processes.

Correct Answer: False

Solution:

The volume of air remaining in the lungs after a normal expiration is known as the Functional Residual Capacity (FRC), which includes the Expiratory Reserve Volume (ERV) and the Residual Volume (RV).

Correct Answer: False

Solution:

The partial pressure of oxygen (pO₂) is higher in the atmospheric air compared to the alveolar air.

Correct Answer: True

Solution:

The excerpt states that insects have a network of tracheal tubes to transport atmospheric air within the body.

Correct Answer: True

Solution:

Carbon dioxide's higher solubility compared to oxygen allows it to diffuse more readily through biological membranes.

Correct Answer: False

Solution:

Frogs can respire through their moist skin (cutaneous respiration) as well as through their lungs.

Correct Answer: False

Solution:

The oxygen dissociation curve is sigmoidal, not a straight line, when plotted against the partial pressure of oxygen.

Correct Answer: False

Solution:

Residual volume is the volume of air remaining in the lungs after a forcible expiration, not a normal expiration.

Correct Answer: True

Solution:

The sigmoidal shape of the oxygen dissociation curve is due to the cooperative binding of oxygen to hemoglobin, where the binding of one oxygen molecule increases the affinity for the next.

Correct Answer: True

Solution:

Oxygen is primarily transported by red blood cells as oxyhaemoglobin, with 97% of it being carried this way.

Correct Answer: True

Solution:

Systems biology emphasizes that interactions among components like molecules, cells, and tissues lead to emergent properties in living phenomena.

Correct Answer: True

Solution:

CO₂ is 20-25 times more soluble in blood than O₂, which enhances its diffusion across membranes.

Correct Answer: True

Solution:

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

Correct Answer: True

Solution:

Approximately 97% of oxygen is transported by red blood cells (RBCs) in the blood, primarily bound to hemoglobin.

Correct Answer: True

Solution:

Insects have a specialized respiratory system consisting of tracheal tubes that facilitate the direct transport of air to body tissues.

Correct Answer: True

Solution:

The oxygen dissociation curve is sigmoidal due to the cooperative binding of oxygen to hemoglobin.

Correct Answer: True

Solution:

The excerpt states that the solubility of CO₂ is 20-25 times higher than that of O₂.

Correct Answer: False

Solution:

The oxygen dissociation curve is sigmoidal, not linear, indicating the relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin.

Correct Answer: True

Solution:

During inspiration, the diaphragm and intercostal muscles contract, increasing the thoracic volume and drawing air into the lungs.

Correct Answer: False

Solution:

The partial pressure of oxygen in the alveoli is lower than in the atmospheric air, which facilitates the diffusion of oxygen into the blood.

Correct Answer: True

Solution:

The excerpt provides data showing that the partial pressure of oxygen is higher in the alveoli compared to the tissues, facilitating the diffusion of oxygen from alveoli to tissues.

Correct Answer: False

Solution:

The partial pressure of oxygen (pO₂) is higher in the atmospheric air (159 mm Hg) compared to the alveolar air (104 mm Hg).

Correct Answer: False

Solution:

The oxygen dissociation curve is sigmoidal in shape, reflecting the cooperative binding of oxygen to hemoglobin.

Correct Answer: True

Solution:

Carbon dioxide is 20-25 times more soluble in blood than oxygen, which facilitates its transport and exchange.

Correct Answer: False

Solution:

Insects do not use lungs; they have a network of tracheal tubes to transport atmospheric air within their bodies.

Correct Answer: False

Solution:

During expiration, the diaphragm relaxes and moves upward, reducing the thoracic volume and increasing the pressure to expel air from the lungs.

Correct Answer: False

Solution:

During expiration, the diaphragm relaxes and moves upwards, reducing the thoracic volume and increasing pressure to expel air.

Correct Answer: True

Solution:

The reductionist approach resulted in the use of physico-chemical concepts and techniques, as mentioned in the excerpts.

Correct Answer: False

Solution:

The oxygen dissociation curve is sigmoidal due to the cooperative binding of oxygen to hemoglobin.

Correct Answer: True

Solution:

The partial pressure of oxygen (pO₂) in the alveoli is 104 mm Hg, which is lower than the atmospheric air pO₂ of 159 mm Hg.

Correct Answer: False

Solution:

About 97% of oxygen is transported in the blood bound to hemoglobin in red blood cells, while only about 3% is dissolved in plasma.

Correct Answer: True

Solution:

The reductionist approach involves studying life forms by analyzing their simplest components, often using physico-chemical concepts and techniques.

Correct Answer: True

Solution:

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

Correct Answer: False

Solution:

In vertebrates, the primary respiratory organs are lungs, except for fishes which use gills.

Breathing and Exchange of Gases

Learning Objectives

Learning Objectives

Revision Notes & Summary

Chapter 14: Breathing and Exchange of Gases

14.1 Respiratory Organs

14.2 Mechanism of Breathing

14.3 Exchange of Gases

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

14.4 Transport of Gases

14.5 Regulation of Respiration

14.6 Disorders of Respiratory System

Important Diagrams

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips

Common Pitfalls

Tips for Exam Preparation

AI Learning Assistant

Practice Test – MCQs, True/False

Multiple Choice Questions

Q1.Which of the following best describes the oxygen dissociation curve?

Correct Answer: B

Q2.Consider a patient with a respiratory disorder that increases the thickness of the alveolar membrane. What would be the most likely effect on the diffusion of gases?

Correct Answer: B

Q3.A patient is experiencing hypoxia at high altitudes. Which of the following physiological changes would most likely occur to improve oxygen delivery to tissues?

Correct Answer: C

Q4.In which form is the majority of carbon dioxide transported in the blood?

Correct Answer: B

Q5.Which of the following factors would most likely increase the affinity of hemoglobin for oxygen in the lungs?

Correct Answer: B

Q6.What is the approximate partial pressure of oxygen (pO₂) in the alveoli, according to the data provided?

Correct Answer: B

Q7.In an experimental setup, the partial pressure of carbon dioxide (pCO2pCO_2pCO2​) in the alveoli is measured to be 40 mm Hg. What would be the expected pCO2pCO_2pCO2​ in the systemic veins?

Correct Answer: A

Q8.What is the effect of high partial pressure of carbon dioxide (pCO2pCO_2pCO2​) on oxygen transport?

Correct Answer: B

Q9.Which of the following best describes the function of haemoglobin in the transport of gases?

Correct Answer: C

Q10.A researcher is studying the oxygen dissociation curve of a novel hemoglobin variant. If this variant shows a leftward shift in the curve, what can be inferred about its affinity for oxygen?

Correct Answer: A

Q11.Which of the following best describes the process of inspiration under normal conditions?

Correct Answer: B

Q12.Which of the following is NOT a factor affecting the binding of oxygen to hemoglobin?

Correct Answer: D

Q13.During heavy exercise, which of the following changes occur in the oxygen dissociation curve?

Correct Answer: B

Q14.What is the primary site for the exchange of gases in the human respiratory system?

Correct Answer: C

Q15.Consider a patient with a novel hemoglobin variant that has a higher affinity for CO₂ than normal hemoglobin. What is the most likely effect on oxygen transport?

Correct Answer: B

Q16.Which of the following factors does NOT affect the rate of diffusion of gases in the respiratory system?

Correct Answer: C

Q17.What is the primary site of gas exchange in the human respiratory system?

Correct Answer: C

Q18.In a hypothetical scenario, a patient is diagnosed with a condition that causes a decrease in the partial pressure of oxygen (pO2pO_2pO2​) in the alveoli to 80 mm Hg. Which of the following physiological responses is most likely to occur?

Correct Answer: A

Q19.A patient with emphysema has difficulty expelling air from the lungs. Which of the following lung volumes is most likely to be affected?

Correct Answer: C

Q20.Which of the following best describes the role of the diaphragm during inspiration?

Correct Answer: B

Q21.Which of the following conditions is most favorable for the dissociation of oxygen from oxyhaemoglobin in the tissues?

Correct Answer: B

Q22.Which of the following respiratory volumes is directly involved in calculating the Functional Residual Capacity (FRC)?

Correct Answer: B

Q23.In the context of human physiology, which of the following best describes the role of the diaphragm during the process of inspiration?

Correct Answer: A

Q24.Which of the following best describes vital capacity?

Correct Answer: B

Q25.Which of the following structures is primarily responsible for the exchange of gases in the human respiratory system?

Correct Answer: A

Q26.A patient is diagnosed with a condition that causes a significant decrease in the inspiratory reserve volume (IRV). What impact would this have on the patient's vital capacity (VC)?

Correct Answer: B

Q27.In a spirometry test, a patient is asked to breathe in as deeply as possible and then exhale forcefully. Which lung capacity is being measured?

Correct Answer: C

Q28.In a hypothetical scenario where atmospheric pressure is 760 mm Hg, if the partial pressure of oxygen (pO2pO_2pO2​) in the alveolar air is 104 mm Hg, what would be the approximate partial pressure of oxygen in the atmospheric air?

Correct Answer: A

Q29.If a person has a tidal volume (TV) of 500 mL, an inspiratory reserve volume (IRV) of 3000 mL, and an expiratory reserve volume (ERV) of 1100 mL, what is their vital capacity (VC)?

Correct Answer: B

Q30.Consider a novel respiratory disorder that increases the thickness of the alveolar membrane by 50%. What is the most likely effect on the diffusion of gases?

Correct Answer: B