Class 11 Biology Chapter 14 Breathing And Exchange Of Gases

Key Concept: Thoracic Volume

c) Thoracic volume increases.

[Solution Description] During inspiration, the diaphragm and external intercostal muscles contract, causing the thoracic cavity to enlarge. As a result, the thoracic volume increases, reducing intra-pulmonary pressure below atmospheric pressure, allowing air to enter the lungs.

Key Concept: Sequential Process

c) Food is directed to the esophagus

[Solution Description] Once the epiglottis covers the glottis, food is directed towards the esophagus. This ensures that food does not enter the respiratory tract, which could cause choking or aspiration.

Key Concept: Cause Identification

b) Cigarette smoking

[Solution Description] The major cause of emphysema is cigarette smoking, which leads to the damaging of alveolar walls.

Key Concept: Conducting vs. Exchange Parts of Respiratory System

c) Conducting part carries out no gas exchange; exchange part facilitates gas exchange.

[Solution Description] The conducting part of the respiratory system (nostrils to terminal bronchioles) is involved in filtering, warming, and humidifying the air before it reaches the exchange surfaces. The exchange part, mainly the alveoli, is where actual gas exchange occurs between air and blood.

Key Concept: Basic Measurement

b) 500 mL

[Solution Description] Tidal Volume (TV) is the amount of air inhaled or exhaled during normal breathing, which for a healthy adult is approximately 500 mL.

Key Concept: Solubility and Diffusion

c) Carbon dioxide (CO2)

[Solution Description] According to the syllabus, CO2 is 20-25 times more soluble than O2. This increased solubility means CO2 can diffuse more readily through the respiratory membrane compared to O2. Hence, CO2 is more soluble in blood.

Key Concept: Basic Definition

a) Inflammation of bronchi and bronchioles

[Solution Description] Asthma is primarily characterized by the inflammation of the bronchi and bronchioles, which leads to symptoms such as wheezing and shortness of breath.

Key Concept: Oxygen Transport

d) As oxyhaemoglobin

[Solution Description] Oxygen is primarily transported in the blood bound to hemoglobin as oxyhaemoglobin. Approximately 98% of the oxygen in the blood is carried this way, with only a small fraction dissolved directly in the plasma.

Key Concept: Structural-Functional Correlation, Pathophysiological Analysis

c) Collapse of airway passage during inhalation, reducing airflow

[Solution Description] The cartilaginous rings provide structural support to prevent airway collapse during inhalation when negative pressure is generated in the respiratory pathways. A defect like weakening or damage could result in an inability to maintain open airways, leading to partial or complete collapse of the trachea or bronchi, which can greatly hinder airflow.

Key Concept: Connection to Trachea

d) Trachea

[Solution Description] The larynx acts as a conduit for air between the pharynx and the trachea. It connects directly to the trachea, ensuring the flow of air into the lower respiratory tract.

Key Concept: Structural Relationships

c) Trachea

[Solution Description] The trachea and bronchi are supported by incomplete cartilaginous rings that provide structural integrity while allowing flexibility. These rings prevent collapse during breathing.

Key Concept: Oxygen Transport

d) As oxyhaemoglobin

[Solution Description] Most oxygen in the blood is transported bound to hemoglobin as oxyhaemoglobin.

Key Concept: Scenario-Based

b) 3320 mL

[Solution Description]

Using the formula $IC = TV + IRV$, substitute the values: $IC = 520 \text{ mL} + 2800 \text{ mL} = 3320 \text{ mL}$.

Thus, the Inspiratory Capacity is 3320 mL.

Key Concept: Integrated Regulation, Impact of CO2 Levels

b) They enhance the activity of both centers, increasing respiratory rate.

[Solution Description]

Elevated levels of CO$_2$ are detected by the chemosensitive area adjacent to the respiratory rhythm center in the medulla. This triggers an increase in the rate and depth of breathing to expel CO$_2$. The pneumotaxic center in the pons helps moderate this response by adjusting the timing and pattern of breaths to ensure efficient gas exchange without overreaction.

Thus, elevated CO$_2$ causes increased activity in both the medulla and pons, working together to stabilize breathing patterns.

Key Concept: Basic Concept

b) Sigmoid

[Solution Description] The oxygen dissociation curve, which represents the relationship between the partial pressure of O$_2$ and hemoglobin saturation, is known to be sigmoid in shape due to cooperative binding of O$_2$ with hemoglobin.

Key Concept: Functional Relationships

c) Alveoli

[Solution Description] The alveoli are tiny sacs within the lungs where the exchange of oxygen and carbon dioxide occurs between the air in the alveoli and the blood in the surrounding capillaries.

Key Concept: Process Understanding

c) Conducting part

[Solution Description] The conducting part of the respiratory system, which includes structures from the external nostrils to the terminal bronchioles, is responsible for filtering out dust and other particles, warming, and humidifying the incoming air before it reaches the alveoli. These processes are essential for protecting the delicate tissues involved in gas exchange.

Key Concept: Comparative Solubility, Haemoglobin Binding Dynamics

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description]

To evaluate both the assertion and reason, we need to understand how CO$_2$ is transported in the blood. CO$_2$ reacts with water to form carbonic acid ($H_2CO_3$), a reaction catalyzed by carbonic anhydrase present in RBCs. This carbonic acid then dissociates into bicarbonate ions ($HCO_3^-$) and hydrogen ions ($H^+$). The presence of carbonic anhydrase makes this process very fast, thus allowing for efficient conversion of CO$_2$ to bicarbonate ions, which accounts for approximately 70% of CO$_2$ transport.

The assertion is true as bicarbonate ions are the primary form of CO$$_2$$ transport due to their stability in blood plasma. The reason is also true since the high concentration of carbonic anhydrase in RBCs indeed speeds up the conversion process, facilitating rapid transport of CO$$_2$$. However, while both statements are correct, the reason does not directly explain why bicarbonate ions are the primary form of transport; instead, it explains the efficiency of the conversion process facilitated by the enzyme. Thus, the correct option is b).

Key Concept: Process Understanding

b) Diaphragm contracts; thoracic volume increases

[Solution Description] During inspiration, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity. This decrease in pressure allows air to flow into the lungs due to the pressure difference between the atmosphere and the thoracic cavity. Thus, the thoracic volume increases, facilitating the intake of air.

Key Concept: Basic Definition

c) Dust production

[Solution Description] The primary cause of occupational respiratory disorders in industries such as stone-breaking is dust production. This is because the process generates fine particles that can be inhaled, leading to potential lung issues.

Key Concept: Hemoglobin Capacity

d) 4

[Solution Description] Hemoglobin is a protein in red blood cells that consists of four subunits. Each subunit can bind one molecule of O$_2$. Therefore, a single hemoglobin molecule can bind up to four O$_2$ molecules simultaneously.

Key Concept: Basic Definition

c) To provide oxygen for metabolism and remove carbon dioxide

[Solution Description] The primary function of respiration in living organisms is to utilize oxygen for metabolism which leads to energy production and removal of carbon dioxide.

Key Concept: Muscle Function

b) Diaphragm

[Solution Description]

The diaphragm is the main muscle involved in breathing. It contracts and flattens during inspiration, increasing thoracic cavity volume and decreasing pressure to draw air in.

Key Concept: Application in Diagnosis

b) It assists in diagnosing restrictive and obstructive lung diseases

[Solution Description] Total Lung Capacity (TLC) provides valuable information in diagnosing respiratory conditions because it includes all lung volumes: Residual Volume (RV), Expiratory Reserve Volume (ERV), Tidal Volume (TV), and Inspiratory Reserve Volume (IRV). Knowing TLC helps clinicians determine if a patient has restrictive or obstructive lung diseases, as these conditions affect the different components of TLC.

Key Concept: Conceptual Understanding

c) Shifts the curve to the left

[Solution Description] A decrease in $pCO_2$ leads to an increase in blood pH, which causes the oxygen dissociation curve to shift to the left. This indicates that hemoglobin’s affinity for oxygen increases, meaning that more oxygen is bound at lower partial pressures.

Key Concept: Basic Concept

c) Oxygen acts as a final electron acceptor in energy production.

[Solution Description] Oxygen is essential for cellular metabolism as it acts as a final electron acceptor in the process of oxidative phosphorylation within the mitochondria, enabling ATP production.

Key Concept: Basic Definition

c) Fibrosis

[Solution Description] Long-term exposure to dust can lead to a condition where lung tissues become scarred, known as fibrosis.

Key Concept: Basic Concept

c) Carbon Dioxide

[Solution Description] The chemosensitive area, located near the respiratory rhythm center in the medulla, is primarily sensitive to changes in levels of $CO_2$ and $H^+$ ions in the blood. An increase in $CO_2$ concentration leads to an increase in $H^+$ ions due to conversion facilitated by carbonic anhydrase, which then stimulates the chemosensitive area to regulate respiration.

Key Concept: Comparative Analysis

c) EC includes Tidal Volume and Expiratory Reserve Volume, while FRC includes Expiratory Reserve Volume and Residual Volume.

[Solution Description] Expiratory Capacity (EC) includes Tidal Volume and Expiratory Reserve Volume, while Functional Residual Capacity (FRC) includes Expiratory Reserve Volume and Residual Volume. So, they measure different aspects of lung volume capacities and are not equivalent.

Key Concept: Real-world Application, Advanced Diffusion Concepts

b) Decreased diffusion due to reduced partial pressure gradient

[Solution Description] At higher altitudes, the atmospheric pressure decreases, reducing the partial pressure of oxygen in the air. According to Dalton’s law, the reduction in partial pressure leads to a decrease in the gradient for oxygen diffusion from alveoli to blood. This results in decreased efficiency of gas exchange, as the driving force for diffusion is weaker.

Key Concept: Basic Definition

c) Proliferation of fibrous tissues

[Solution Description] Fibrosis refers to the proliferation of fibrous tissues within the lungs due to chronic inflammation or exposure to harmful substances, such as dust.

Key Concept: Clinical Relevance

d) It assists in diagnosing restrictive and obstructive lung diseases.

[Solution Description] Vital Capacity (VC) measurement is crucial because it helps diagnose lung diseases by assessing the volume of air a person can expel from the lungs after a forced inspiration. It identifies potential restrictive or obstructive pulmonary conditions, thus aiding clinicians in developing appropriate treatment plans.

Key Concept: Basic Definition

c) A chronic disorder where alveolar walls are damaged, decreasing respiratory surface.

[Solution Description] Emphysema is described as a chronic disorder where damage to the alveolar walls occurs, leading to a decreased respiratory surface and impaired gas exchange.

Key Concept: Haemoglobin Function

c) It binds O2 to form oxyhaemoglobin

[Solution Description] Haemoglobin binds with oxygen to form oxyhaemoglobin, allowing for efficient oxygen transport in the blood.

Key Concept: Comparative Anatomy

c) Conducting part transports air; exchange part exchanges gases

[Solution Description] The conducting part of the respiratory system includes structures that transport air from the external nostrils to terminal bronchioles without participating in gas exchange. In contrast, the exchange part consists of alveoli and their ducts where actual gas exchange occurs through diffusion.

Key Concept: Application of Concepts

c) 4400 mL

[Solution Description]

To calculate Vital Capacity (VC), we use the formula:

$VC = IRV + TV + ERV$

Substituting the given values:

$VC = 2800 \, \text{mL} + 500 \, \text{mL} + 1100 \, \text{mL} = 4400 \, \text{mL}$

Therefore, the Vital Capacity (VC) for this patient is 4400 mL.

Key Concept: Organ Identification

c) Gills

[Solution Description] Fish primarily use gills for gas exchange because they live in aquatic environments where these structures can efficiently extract dissolved oxygen from water.

Key Concept: Diffusion Factors

a) Temperature

[Solution Description] The rate of diffusion of gases across the alveolar membrane is influenced by factors such as partial pressure gradients, solubility of gases, and the thickness of the respiratory membrane. Among these, the temperature can also indirectly influence the solubility of gases.

Key Concept: Structural Analysis

b) Vascularized structure

[Solution Description] The vascularized structure of the lungs increases the surface area available for gas exchange, allowing more efficient transfer of oxygen into the blood and removal of carbon dioxide from it. This adaptation enables terrestrial vertebrates to extract oxygen more efficiently from the air.

Key Concept: Integrated Regulation, Complex Interactions

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description]

The assertion claims that the respiratory rhythm centre relies solely on the chemosensitive area’s input for regulation. This is not entirely true because, although the chemosensitive area provides critical information regarding CO$_2$ and H$^+$ levels, the respiratory rhythm centre also receives input from other sources such as the pneumotaxic centre in the pons. The pneumotaxic centre helps adjust the breathing rate by moderating the activity of the respiratory rhythm centre, especially during different states like exercise or rest. Therefore, the reason, which accurately describes the role of the pneumotaxic centre in modulating signals, does not serve as a correct explanation for the assertion. Thus, the answer is option b).

Key Concept: Oxygen’s Role

d) Minor role

[Solution Description] Oxygen plays a minor role in the regulation of respiratory rhythm. The major regulators are carbon dioxide and hydrogen ions, which influence the chemosensitive area in the medulla. This is explicitly stated in the syllabus.

Key Concept: Basic Function

b) To control respiratory rhythm

[Solution Description] The respiratory rhythm center in the medulla oblongata is responsible for regulating the basic rhythm of respiration. This involves setting the pace and timing at which breathing occurs without conscious effort.

Key Concept: Oxygen Binding

c) Partial pressure of O$_2$

[Solution Description] The primary factor influencing the binding of oxygen to haemoglobin is the partial pressure of oxygen ($pO_2$). A higher $pO_2$ increases the likelihood of oxygen binding to haemoglobin.

Key Concept: Oxygen Transport

b) As oxyhaemoglobin

[Solution Description] Oxygen is primarily transported in the blood bound to haemoglobin, forming oxyhaemoglobin.

Key Concept: Diffusion Factors

c) Color of blood

[Solution Description] The solubility of gases, thickness of membranes, and pressure gradient all affect the rate of diffusion. However, color of blood does not impact gas diffusion.

Key Concept: Gas Exchange Dynamics, Physiological Mechanism

c) Increased $pO_2$ gradient between alveoli and blood

[Solution Description] During intense exercise, the body’s demand for oxygen increases, and thus more oxygen needs to diffuse from the alveoli into the blood. The primary factor that facilitates this increased diffusion is an increased pressure gradient for $O_2$. As the body uses more oxygen, the partial pressure of oxygen ($pO_2$) in the blood decreases, increasing the difference between the $pO_2$ in the alveoli and the blood. This higher gradient drives more oxygen to diffuse into the bloodstream.

Key Concept: Application in Diagnosis

b) Emphysema

[Solution Description]

An increase in Functional Residual Capacity (FRC) can often be seen in conditions where there is difficulty in expelling air, such as Chronic Obstructive Pulmonary Disease (COPD). Emphysema, a type of COPD, leads to hyperinflation of the lungs and increases FRC due to trapped air. This results in increased residual lung volume.

Key Concept: Simple Calculation

a) 4000 mL

[Solution Description] To find the IRV, we use the relation $IC = TV + IRV$. Given $IC = 4500$ mL and $TV = 500$ mL:

$IRV = IC – TV = 4500 \, \text{mL} – 500 \, \text{mL} = 4000 \, \text{mL}$

Therefore, the Inspiratory Reserve Volume is $4000$ mL.

Key Concept: Calculation of Minute Ventilation

b) 6000 mL

[Solution Description]

The minute ventilation can be calculated by multiplying the tidal volume (TV) by the breathing rate. Given that TV = 500 mL and the breathing rate = 12 breaths/min, the calculation is as follows:

$\text{Minute Ventilation} = \text{Tidal Volume} \times \text{Breathing Rate}$

$\text{Minute Ventilation} = 500 \, \text{mL/breath} \times 12 \, \text{breaths/minute} = 6000 \, \text{mL/minute}$

Therefore, the minute ventilation is 6000 mL.

Key Concept: Environmental Challenges, Comparative Efficiency

c) Pulmonary respiration

[Solution Description] In polluted environments, the efficiency of cutaneous respiration decreases due to skin infections reducing gas exchange. Therefore, amphibians must depend more heavily on their lungs for oxygen intake as pulmonary respiration becomes more crucial when cutaneous absorption is ineffective.

Key Concept: Simple Calculation

d) 2100 mL

[Solution Description]

Functional Residual Capacity (FRC) is calculated by adding Expiratory Reserve Volume (ERV) and Residual Volume (RV).

Using the formula:

$$FRC = ERV + RV$$

Given:

\begin{align*}

ERV &= 900 \text{ mL}

RV &= 1200 \text{ mL}

\end{align*}

Calculate $FRC$:

\begin{align*}

FRC &= 900 + 1200

FRC &= 2100 \text{ mL}

\end{align*}

Therefore, the Functional Residual Capacity (FRC) is 2100 mL.

Key Concept: Membrane Thickness

a) Less than a millimeter

[Solution Description] The total thickness of the diffusion membrane is less than a millimeter, allowing efficient gas exchange to occur between the alveoli and blood.