Chapter 14. Breathing and Exchange of Gases

Class 11 Biology Chapter 14 Breathing and Exchange of Gases Exercise Questions and Answers :

1. Define vital capacity. What is its significance?

Answer : The maximum volume of air a person can breathe in after a forced expiration. This includes ERV, TV and IRV or the maximum volume of air a person can breathe out after a forced inspiration.

Vital capacity is a significant clinical parameter for assessing lung health, diagnosing respiratory diseases, monitoring disease progression, and evaluating the effects of treatments and interventions. It plays a vital role in managing and maintaining respiratory health.

2. State the volume of air remaining in the lungs after a normal breathing .

Answer : The volume of air left in the lungs after a normal breath is known as the "Functional Residual Capacity" (FRC). It comprises the Expiratory Reserve Volume (ERV) and the Residual Volume (RV). FRC is important for maintaining lung function and gas exchange, as it ensures that there is always some air left in the lungs, preventing lung collapse and allowing for continuous oxygen and carbon dioxide exchange. The FRC typically ranges from 2100 mL to 2300 mL.

3. Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?

Answer :  Diffusion of gases occurs in the alveolar region only because the alveoli are the thin, vascularized structures where actual gas exchange takes place. The conducting part of the respiratory system, including tracheae and bronchi, lacks the thin, irregular-walled structures necessary for efficient gas exchange. The alveoli provide a large surface area for the exchange of oxygen and carbon dioxide between the blood and atmospheric air. The rest of the respiratory system primarily functions to transport, filter, humidify, and condition the air.

4. What are the major transport mechanisms for ? Explain.

Answer :  The major transport mechanisms for carbon dioxide () in the blood are :

(a) Carbamino-Hemoglobin Formation: Approximately 20-25% of  is carried in the blood by binding to hemoglobin as carbamino-hemoglobin. The extent of this binding is influenced by the partial pressure of (). When the is high, such as in tissues where is produced during metabolism, more molecules bind to hemoglobin. This binding is also influenced by the partial pressure of oxygen (), with higher favoring binding to hemoglobin.

(b) Bicarbonate Ion () Formation: The majority of (about 70%) is transported as bicarbonate ions in the blood. Inside red blood cells (RBCs), carbonic anhydrase, an enzyme with high concentration in RBCs, facilitates the reversible chemical reaction between and water :

 

In the tissues, where levels are high due to metabolic activity, diffuses into the blood, forming bicarbonate ions and hydrogen ions. This allows to be transported from the tissues to the lungs as bicarbonate ions. In the alveoli, where is low, the reaction reverses, leading to the release of from bicarbonate ions, which can then be exhaled.

These transport mechanisms ensure the efficient transfer of from the tissues, where it is produced as a waste product of metabolism, to the alveoli, where it can be exhaled from the body. The ability of to bind with hemoglobin and form bicarbonate ions is tightly regulated and helps maintain acid-base balance in the body. Approximately 4 ml of is delivered to the alveoli for every 100 ml of deoxygenated blood, contributing to the removal of excess from the body.

5. What will be the and in the atmospheric air compared to those in the alveolar air ?

(i) lesser, higher

(ii) higher, lesser

(iii) higher, higher

(iv) lesser, lesser

Answer : (ii) higher, lesser.

In atmospheric air, is relatively high (around 159 mmHg), and is low (about 0.3 mmHg).

In alveolar air, after gas exchange in the lungs, is lower (around 104 mmHg), and is higher (about 40 mmHg).

6. Explain the process of inspiration under normal conditions.

Answer :  Under normal conditions, the process of inspiration, the first stage of breathing, is initiated by the contraction of the diaphragm and external intercostal muscles. When the diaphragm contracts, it flattens and increases the volume of the thoracic chamber in the antero-posterior axis. Simultaneously, the external intercostal muscles lift the ribs and sternum, causing an increase in the thoracic chamber's dorso-ventral volume. This overall increase in thoracic volume leads to a corresponding increase in pulmonary volume. As the pulmonary volume increases, the intra-pulmonary pressure drops below atmospheric pressure, creating a pressure gradient that allows atmospheric air to be drawn into the lungs.

  

This process is known as inspiration, enabling fresh air to enter the respiratory system for oxygen exchange. Relaxation of the diaphragm and intercostal muscles leads to expiration, where the increased intra-pulmonary pressure forces air out of the lungs. The diaphragm and intercostal muscles play key roles in generating pressure gradients for the movement of air during normal breathing.

7. How is respiration regulated?

Answer : Respiration is regulated primarily by the neural system in human beings. The respiratory rhythm center, located in the medulla region of the brain, plays a central role in this regulation. Another center, the pneumotaxic center in the pons region, can modulate the respiratory rhythm center's functions, affecting the duration of inspiration and respiratory rate. Additionally, a chemosensitive area adjacent to the rhythm center is highly sensitive to and hydrogen ions. Changes in these substances can activate this area, leading to adjustments in the respiratory process to eliminate them. Receptors in the aortic arch and carotid artery also detect changes in and levels and signal the rhythm center for corrective actions. Oxygen's role in regulating respiratory rhythm is relatively insignificant.

8. What is the effect of on oxygen transport?

Answer : The partial pressure of carbon dioxide () has a significant effect on oxygen transport in the blood. An increase in , as seen in conditions such as hypercapnia (elevated levels), causes a decrease in blood  . This acidosis weakens the oxygen-hemoglobin affinity, making it harder for hemoglobin to bind with oxygen. Consequently, oxygen is less effectively loaded in the lungs and delivered to body tissues, impairing oxygen transport and potentially leading to tissue hypoxia.

9. What happens to the respiratory process in a man going up a hill?

Answer : As a person ascends a hill, the respiratory process is affected due to lower oxygen levels at higher altitudes. In response, the body tends to breathe more rapidly. This increased breathing rate helps to compensate for the lower oxygen availability, ensuring that sufficient oxygen is taken in with each breath. By breathing more rapidly, the body aims to maintain adequate oxygenation of the blood, enabling the individual to meet the oxygen demands while ascending to higher altitudes.

10. What is the site of gaseous exchange in an insect?

Answer : In insects, the site of gaseous exchange occurs through a network of tiny air tubes called tracheae. These tracheae directly connect with the insect's body cells, allowing for the exchange of oxygen and carbon dioxide. Gaseous exchange in insects takes place passively by diffusion, as air enters the tracheal system through small openings called spiracles and travels through the tracheae to reach the cells, where oxygen is delivered and carbon dioxide is removed.

11. Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?

Answer :  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 (). Hemoglobin is a red iron-containing pigment in red blood cells that can reversibly bind with oxygen to form oxyhemoglobin. Each hemoglobin molecule can bind up to four oxygen molecules. The sigmoidal or S-shaped pattern of the curve is due to the cooperative binding of oxygen molecules to hemoglobin.

The sigmoidal shape is primarily influenced by factors like , hydrogen ion () concentration, and temperature. In the alveoli, where conditions are favorable for oxygen binding (high , low , lower concentration, and lower temperature), hemoglobin readily binds with oxygen. In contrast, in the tissues, where conditions favor oxygen release (low , high , high concentration, and higher temperature), oxygen dissociates from hemoglobin. This cooperative binding and release of oxygen at different tissue sites are represented by the sigmoidal oxygen dissociation curve. It illustrates how hemoglobin's affinity for oxygen changes with varying levels, facilitating efficient oxygen transport and delivery to body tissues. Under normal physiological conditions, around 5 ml of oxygen is delivered to the tissues for every 100 ml of oxygenated blood.

12. Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.

Answer : Hypoxia is a medical condition characterized by an inadequate supply of oxygen to body tissues. It can result from various causes and can affect different parts of the body.

There are several types of hypoxia are :

(i) Hypoxic Hypoxia : This is the most common type of hypoxia and occurs when there is insufficient oxygen in the air, such as at high altitudes or in situations where oxygen levels are low, like in a sealed room.

(ii) Anemic Hypoxia : This type of hypoxia occurs when there is a reduced oxygen-carrying capacity of the blood, often due to anemia or other blood disorders.

(iii) Ischemic Hypoxia : It results from poor blood flow, preventing the delivery of oxygen to tissues. Conditions like circulatory problems or shock can lead to ischemic hypoxia.

(iv) Hypoxic Hypoxia : In this type, the blood cannot carry enough oxygen due to problems with hemoglobin, such as in carbon monoxide poisoning or certain hemoglobin disorders.

(v) Histotoxic Hypoxia : This occurs when the body's tissues are unable to use the oxygen that is delivered to them due to the presence of toxins, such as alcohol or drugs.

Hypoxia can lead to a range of symptoms, including shortness of breath, confusion, dizziness, rapid heartbeat, and in severe cases, it can result in loss of consciousness or even death. Treating hypoxia typically involves addressing the underlying cause, such as providing supplemental oxygen or improving blood circulation.

It's essential to be aware of the causes and symptoms of hypoxia, as it can have serious consequences if not recognized and treated promptly. Discussing this topic with friends and colleagues can help raise awareness and promote safety, especially in situations where there is a risk of reduced oxygen supply, such as during high-altitude travel or in certain work environments.

13. Distinguish between

(a) IRV and ERV

(b) Inspiratory capacity and Expiratory capacity.

(c) Vital capacity and Total lung capacity.

Answer : (a) The difference between IRV and ERV :

Inspiratory Reserve Volume (IRV)	Expiratory Reserve Volume (ERV)
IRV is the additional volume of air that can be inhaled forcefully after a normal inhalation.	ERV is the additional volume of air that can be exhaled forcefully after a normal exhalation.
IRV is typically greater in volume than ERV. It represents the maximal amount of air that can be inhaled beyond a normal breath.	ERV is typically smaller in volume than IRV. It represents the maximal amount of air that can be exhaled beyond a normal breath.
IRV is measured by inhaling as deeply as possible after taking a normal breath and recording the additional air inhaled.	ERV is measured by exhaling as forcefully as possible after taking a normal breath and recording the additional air exhaled.
IRV is important during activities that require increased oxygen intake, such as strenuous exercise. It helps meet the increased oxygen demand.	ERV is significant when there's a need to forcefully expel air, like during activities that involve coughing or forced exhalation. It assists in clearing airways and removing irritants.
IRV tends to decrease with age as lung elasticity decreases.	ERV may also decrease with age due to reduced lung compliance.
IRV is part of the inspiratory capacity (IC) and is essential for deep inhalation.	ERV is part of the expiratory capacity (EC) and aids in forceful exhalation.
Example : Taking a deep breath before singing a high note in a song is an example of using IRV.	Example : Exhaling forcefully when blowing out birthday candles is an example of using ERV.

(b) The difference between Inspiratory Capacity (IC) and Expiratory Capacity (EC) :

Inspiratory Capacity (IC)	Expiratory Capacity (EC)
IC is the maximum volume of air that can be inhaled after a normal exhalation.	EC is the maximum volume of air that can be exhaled after a normal inhalation.
IC is calculated by adding the Tidal Volume (TV) to the Inspiratory Reserve Volume (IRV).	EC is calculated by adding the Tidal Volume (TV) to the Expiratory Reserve Volume (ERV).
IC is usually greater in volume than EC. It represents the maximal inhalation capacity.	EC is usually smaller in volume than IC. It represents the maximal exhalation capacity.
IC is important for activities that require deep inhalation, such as preparing for a deep breath before singing or playing wind instruments.	EC is significant when there's a need to forcefully exhale, such as coughing, sneezing, or blowing out candles on a cake.
IC may decrease with age as lung elasticity and chest wall compliance decrease.	EC may also decrease with age due to changes in lung and chest wall function.
IC represents the maximum amount of air that can be inhaled after a normal breath, reflecting the inspiratory reserve capacity.	EC represents the maximum amount of air that can be exhaled after a normal breath, reflecting the expiratory reserve capacity.

(c) Difference between Vital capacity and Total lung capacity :

Vital Capacity (VC)	Total Lung Capacity (TLC)
VC is the maximum volume of air that can be exhaled after a maximum inhalation.	TLC is the total volume of air that the lungs can hold at the end of a maximum inhalation.
VC is calculated by adding the Tidal Volume (TV), Inspiratory Reserve Volume (IRV), and Expiratory Reserve Volume (ERV).	TLC is the sum of all lung volumes, including TV, IRV, ERV, and  residual volume (RV).
VC is typically smaller in volume than TLC. It represents the maximal exhalation capacity.	TLC is usually greater in volume than VC. It represents the total lung volume, including all air that can be held in the lungs.
VC is essential for activities requiring maximal exhalation, such as forced expiration during exercise or singing.	TLC reflects the entire lung capacity and is used in diagnosing various lung diseases and conditions.
VC may decrease with age due to reduced lung and chest wall compliance.	TLC may also decrease with age, primarily due to changes in lung function and chest wall dynamics.
VC represents the maximum amount of air that can be forcefully exhaled after a deep inhalation, including all available reserve capacities.	TLC reflects the total capacity of the lungs, including both the air that can be inhaled and the air that remains in the lungs after maximal exhalation.
VC can be measured through spirometry.	TLC is measured using various methods, including helium dilution and body plethysmography.
Example : Exhaling as forcefully as possible during a spirometry test measures VC.	Example : Determining the lung capacity of an individual for diagnostic purposes often involves measuring TLC

14. What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.

Answer : Tidal volume (TV) is the volume of air that is inhaled or exhaled during normal, quiet breathing, without any extra effort. It represents the amount of air exchanged with each breath. The approximate value of tidal volume for a healthy adult human is about 500 milliliters (ml) or 0.5 liters (i.e., a healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute.) . On an average, a healthy human breathes 12-16 times/minute.

We know that ,

Tidal Volume per Hour = Tidal Volume (TV) x Breathing Rate per Minute x 60

Tidal Volume per Hour = 500 ml (TV) x 12 breaths/minute x 60 minutes

 = 360,000 ml or 360 liters per hour

And Tidal Volume per Hour = 500 ml (TV) x 16 breaths/minute x 60 minutes

 = 480,000 ml or 480 liters per hour

So, a healthy human would exchange approximately between 360 liters and 480 liters of air (tidal volume) in an hour during quiet, normal breathing .