Breathing and Exchange of Gases

Breathing and exchange of gases are essential processes for all living organisms. In plants, these processes involve the exchange of gases between the plant and the environment.

Gaseous Exchange in Plants

• Photosynthesis: Plants release oxygen and absorb carbon dioxide during photosynthesis.
• Respiration: Plants release carbon dioxide and absorb oxygen during respiration.
• Transpiration: The loss of water vapor through stomata (small pores on leaves) helps in gas exchange.

Respiratory Organs in Animals

• Insects: Tracheal tubes for gas exchange.
• Earthworms: Skin for gas exchange.
• Fish: Gills for gas exchange.
• Amphibians: Lungs and skin for gas exchange.
• Reptiles, Birds, and Mammals: Lungs for gas exchange.

Human Respiratory System

• Nasal Cavity and Oral Cavity: Entry points for air.
• Pharynx: Passageway for both air and food.
• Larynx: Voice box, containing the vocal cords.
• Trachea: Windpipe, leading to the bronchi.
• Bronchi: Divide into smaller bronchioles.
• Lungs: Organs containing alveoli.
• Diaphragm: Muscle that aids in breathing.

Mechanism of Breathing

• Inspiration: Inhalation, drawing air into the lungs.
• Expiration: Exhalation, expelling air from the lungs.

Respiratory Volumes

• Tidal Volume: Normal volume of air inhaled or exhaled in one breath.
• Inspiratory Reserve Volume: Additional volume of air that can be inhaled after a normal inhalation.

Disorders of the Respiratory System

• Asthma: Chronic inflammation of the airways.
• Emphysema: Destruction of alveoli, leading to difficulty breathing.
• Bronchitis: Inflammation of the bronchial tubes.
• Pneumonia: Inflammation of the lungs, often caused by infection.

Exercise

1. Define vital capacity. What is its significance?

Ans : 

Vital capacity is the maximum volume of air that a person can exhale after taking the deepest possible breath. It is a measure of lung function and respiratory strength.

Significance of Vital Capacity:

• Assessing lung health: Vital capacity is a key indicator of lung health and respiratory function. It can be used to diagnose and monitor various respiratory diseases, such as asthma, COPD, and pulmonary fibrosis.
• Evaluating athletic performance: Athletes often have higher vital capacities due to their increased lung strength and endurance.
• Monitoring respiratory function: Regular measurements of vital capacity can help to track changes in lung function over time and identify potential problems early.
• Assessing overall health: A low vital capacity can be a sign of underlying health issues, such as heart disease or neuromuscular disorders.

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

Ans : 

Residual Volume (RV) is the volume of air remaining in the lungs after a normal breathing cycle. It’s the amount of air that cannot be exhaled, even with maximum effort.

The average residual volume in adults is around 1,200 milliliters. It’s important to note that RV can vary depending on factors like age, height, and overall lung health.

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

Ans : 

Diffusion of gases primarily occurs in the alveolar region of the respiratory system due to several factors:

1. Thin Alveolar Walls: The alveoli are tiny, balloon-like structures with extremely thin walls. This thinness allows for efficient diffusion of gases across the membrane.
2. Large Surface Area: The alveoli collectively have a vast surface area, which maximizes the contact between the air and the blood. 
3. Capillary Network: The alveoli are surrounded by a dense network of capillaries, which allows for close contact between the air and blood. This facilitates the diffusion of oxygen into the blood and carbon dioxide out of the blood.
4. Moist Environment: The alveoli are kept moist by a thin layer of surfactant, which helps to maintain the proper gas exchange environment.

4. What are the major transport mechanisms for CO2 ? Explain

Ans : 

Major Transport Mechanisms for CO2:

Carbon dioxide (CO2) is transported from the tissues to the lungs through three primary mechanisms:

1. Dissolved CO2: A small portion of CO2 is transported directly dissolved in the blood plasma.
2. Bicarbonate (HCO3-) Formation: The majority of CO2 reacts with water in red blood cells to form carbonic acid (H2CO3), which then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
3. Carbaminohemoglobin Formation: CO2 binds to hemoglobin, forming carbaminohemoglobin. This reaction occurs primarily in the deoxygenated hemoglobin of venous blood.

CO2 is transported from the tissues to the lungs through a combination of dissolved CO2, bicarbonate formation, and carbaminohemoglobin formation. The relative contributions of these mechanisms vary depending on factors such as blood pH, oxygen saturation, and the concentration of CO2 in the tissues.

5. What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air ? 

(i) pO2 lesser, pCO2 higher 

(ii) pO2 higher, pCO2 lesser 

(iii) pO2 higher, pCO2 higher 

(iv) pO2 lesser, pCO2 lesser

Ans : 

(ii) pO2 higher, pCO2 lesser

6. Explain the process of inspiration under normal conditions.

Ans : 

Inspiration (Inhalation) is the process of drawing air into the lungs. Under normal conditions, it involves the following steps:

1. Diaphragm Contraction: The diaphragm, a dome-shaped muscle below the lungs, contracts and flattens downward.
2. Chest Cavity Expansion: The intercostal muscles between the ribs also contract, causing the chest cavity to expand outward.
3. Pressure Difference: The expansion of the chest cavity creates a lower pressure within the lungs compared to the atmospheric pressure.
4. Air Inflow: Due to this pressure difference, air is drawn into the lungs through the nose and mouth, down the trachea, and into the bronchi and bronchioles.
5. Alveolar Expansion: As air enters the lungs, it fills the tiny air sacs called alveoli, causing them to expand.

7. How is respiration regulated?

Ans : 

Respiration is primarily regulated by the nervous system, specifically by centers in the brainstem.

These centers monitor the levels of carbon dioxide (CO2) and oxygen (O2) in the blood, as well as the pH of the blood.

8.  What is the effect of pCO2 on oxygen transport?

Ans : 

The level of pCO2 (partial pressure of carbon dioxide) has a significant effect on oxygen transport.

When the pCO2 in the blood increases:

• Increased Oxygen Unloading: As a result of the decreased affinity, more oxygen is unloaded from hemoglobin in the tissues, where it is needed.

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

Ans : 

As a person climbs a hill, the respiratory process undergoes several changes to meet the increased demand for oxygen.

1. Increased Breathing Rate: The body senses the increased workload and demands more oxygen. The respiratory centers in the brain signal the diaphragm and intercostal muscles to increase the rate and depth of breathing.
2. Increased Tidal Volume: Each breath becomes deeper, taking in more air. This increases the amount of oxygen available to the body.
3. Increased Cardiac Output: The heart pumps blood faster and harder to deliver oxygen to the working muscles.
4. Shifts in Blood Flow: Blood is redirected away from non-essential organs, such as the digestive system, and towards the muscles and brain.
5. Increased Oxygen Affinity: The hemoglobin in red blood cells becomes more likely to release oxygen to the tissues, a process known as the Bohr effect. This is due to the increased acidity of the blood caused by the buildup of carbon dioxide.
6. Increased Ventilation: The lungs may also increase their ventilation rate to further enhance oxygen intake.

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

Ans : 

The site of gaseous exchange in insects is the tracheal system.

This system consists of a network of tiny tubes, called tracheae, that extend throughout the insect’s body. Oxygen diffuses into the tracheae from the outside air and then diffuses further into the tissues. Carbon dioxide, a waste product of respiration, diffuses out of the tissues into the tracheae and is eventually expelled through the spiracles.

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

Ans : 

An oxygen dissociation curve is a graphical representation that shows the relationship between the partial pressure of oxygen (pO2) and the percentage saturation of hemoglobin with oxygen. It is a vital tool in understanding how oxygen is transported in the blood.  

Sigmoidal Pattern:

The curve has a characteristic S-shape, or sigmoid pattern, due to the cooperative binding of oxygen to hemoglobin. This means that the binding of one oxygen molecule to hemoglobin makes it easier for subsequent oxygen molecules to bind. As a result, the curve becomes steeper as the partial pressure of oxygen increases.

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

Ans : 

Hypoxia is a condition in which the body or a specific tissue receives an inadequate supply of oxygen. 

• High altitude: At high altitudes, the air pressure is lower, leading to a decrease in the available oxygen.
• Respiratory disorders: Conditions like asthma, COPD, or pneumonia can impair lung function and reduce oxygen intake.
• Cardiovascular diseases: Heart failure or other circulatory problems can reduce blood flow to tissues, limiting oxygen delivery.
• Carbon monoxide poisoning: Carbon monoxide binds to hemoglobin more tightly than oxygen, reducing the amount of oxygen available to the body.
• Anemias: Conditions that reduce the number of red blood cells or the amount of hemoglobin in the blood can lead to hypoxia.

13. Distinguish between 

(a) IRV and ERV 

(b) Inspiratory capacity and Expiratory capacity. 

(c) Vital capacity and Total lung capacity.

Ans : 

(a) IRV and ERV 

Feature	Inspiratory Reserve Volume (IRV)	Expiratory Reserve Volume (ERV)
Purpose	Measures the additional air that can be inhaled after a normal inhalation	Measures the additional air that can be exhaled after a normal exhalation
Calculation	IC = TV + IRV	EC = ERV + RV
Normal Values	Approximately 3,000 mL	Approximately 1,200 mL
Affected by	Lung health, age, body size, and exercise	Lung health, age, body size, and posture
Clinical Significance	Used to assess lung function and diagnose respiratory disorders	Used to assess lung function and evaluate respiratory muscle strength

(b) Inspiratory capacity and Expiratory capacity. 

Feature	Inspiratory Capacity (IC)	Expiratory Capacity (EC)
Calculation	IC = TV + IRV	EC = ERV + RV
Purpose	Measures the total amount of air that can be inhaled after a normal exhalation	Measures the total amount of air that can be exhaled after a normal inhalation
Normal Values	Approximately 3,600 mL	Approximately 2,400 mL
Affected by	Lung health, age, body size, and exercise	Lung health, age, body size, and posture
Clinical Significance	Used to assess overall lung function and diagnose respiratory disorders	Used to evaluate exhalation efficiency and respiratory muscle strength

(c) Vital Capacity and Total Lung Capacity

Feature	Vital Capacity (VC)	Total Lung Capacity (TLC)
Calculation	VC = TV + IRV + ERV	TLC = VC + RV
Purpose	Measures the maximum amount of air that can be exhaled after a maximum inhalation	Measures the total volume of air that the lungs can hold
Normal Values	Approximately 4,800 mL	Approximately 6,000 mL
Affected by	Lung health, age, body size, and exercise	Lung health, age, body size, and posture
Clinical Significance	Used to assess overall lung function and diagnose respiratory disorders	Used to evaluate the overall capacity of the lungs

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

Ans : 

Tidal Volume (TV) is the normal volume of air inhaled or exhaled in one breath. It’s a key measure of lung function and typically ranges between 500-600 milliliters in healthy adults.

To find the approximate tidal volume for a healthy human in an hour:

1. Calculate breaths per minute: Assume a normal breathing rate of 12-15 breaths per minute. Let’s use an average of 13 breaths per minute.
2. Calculate breaths per hour: Multiply the breaths per minute by 60 minutes to get the breaths per hour. 
3. 13 breaths/minute * 60 minutes/hour 

= 780 breaths/hour.

4. Calculate total tidal volume: Multiply the tidal volume per breath by the number of breaths per hour. Assuming a tidal volume of 550 mL, the total tidal volume in an hour would be 550 mL/breath * 780 breaths/hour = 429,000 mL or 429 liters.