Breathing And Exchange Of Gases Question And Answers

Biology Class 11 WBCHSE Breathing And Exchange Of Gases Questions And Answers

Question 1. What is the significance of gaseous exchange in the human body?
Answer:

The significance of gaseous exchange in the human body

The body needs energy to perform all important physiological functions. In living cells, glucose and other calorific foods are oxidised to release that energy. For this oxidation, oxygen is required by higher animals.

During the oxidation of glucose and other calorific foods, energy is released and ATP is synthesised.

At the same time, harmful carbon dioxide is generated. This gas may accumulate in the tissues causing cell damage. Thus, for sustaining life, gaseous exchange between oxygen and carbon dioxide is necessary.

Question 2. Respiration is a metabolic reaction but breathing is not.—Explain.
Answer:

Respiration is a metabolic reaction but breathing is not

Respiration is a catabolic reaction. It is because in this case glucose and other calorific foods undergo partial or complete oxidation in the living cells in the presence or absence of oxygen.

ATP synthesis also takes place. But breathing involves the exchange of gases with atmosphere O₂ and CO₂. No energy is produced in humans due to breathing, rather energy is utilised.

Read and Learn More WBCHSE Solutions For Class 11 Biology

Question 3. Why does the trachea not collapse even in the absence of air?
Answer:

The length of the human trachea is about 10-11 cm. Its wall is surrounded by an 11-20 C-shaped cartilage ring. These are actually formed by hyaline cartilages.

The terminal end of each cartilage is connected by elastic fibres and smooth muscle fibres. Due to cartilage rings, the wall of the trachea is elastic and if in the absence of air trachea collapses, then also it regains its shape.

Question 4. State the position and role of the diaphragm in the human respiratory system. Answer:

Position: The Diaphragm is located horizontally, between the thoracic cavity and abdominal cavity, below the two lungs and heart.

Role in respiration:

When the diaphragm contracts, it moves downward, so the volume of the thoracic cavity increases. Intrapulmonary pressure reduces. Then atmospheric O₂ enters the lungs,

When the diaphragm expands, it moves upward and comes back to its normal position, so the volume of the thoracic cavity reduces. Intra-pulmonary pressure increases. As a result, the lungs expire CO₂ from the body.

Breathing and exchange of gases questions and answers PDF

Question 5. How many intercostal muscles are present in the human rib cage? Mention their role in respiration.
Answer:

Number of intercostal muscles: The human rib cage contains 12 pairs of ribs. In between these ribs, 11 external and 11 internal intercostal muscles are present.

Role in respiration:

[When external intercostal muscles contract, ribs move upward and outward. As a result, the thoracic cavity increases and inspiration takes place,

When internal intercostal muscles expand, ribs move downward and inward. As a result, the volume of the thoracic cavity decreases and expiration takes place. State the differences between inspiration capacity (1C) and expiration capacity (EC)

Question 6. How much volume of air is inspired or expired per minute by the lungs of an adult, at rest? What is this volume of air known as?
Answer:

At rest, an adult can inspire or expel approximately 500 ml or 0.5L of air per minute, by the two lungs. This volume of air is known as tidal volume (TV).

Question 7. What is the reason behind the diffusion of oxygen from alveolar air to blood in pulmonary capillaries?
Answer:

The partial pressure of oxygen (PO₂) in alveolar air is approximately 104 mm Hg and PO₂ in pulmonary capillaries is 40 mm Hg.

Due to this pressure gradient, oxygen diffuses from the alveolar air to the blood in capillaries, by crossing the squamous epithelium layer of alveoli and endothelium of capillaries.

NEET breathing and exchange of gases important questions with answers

Question 8. Although the PO₂ in human alveoli is 100-104 mm Hg, yet when oxygen enters the blood by diffusion, its PO₂ never becomes 100-104 mm Hg. Why?
Answer:

Although the PO₂ in human alveoli is 100-104 mm Hg, yet when oxygen enters the blood by diffusion, its PO₂ never becomes 100-104 mm Hg.

The reason behind dissimilar PO₂ is that some amount of oxygen is absorbed by the tissues, present in the walls of the alveoli. It is required for cellular oxidation and energy release. So, the PO₂ in oxygenated blood is 90-95 mm Hg.

Question 9. On which factors does the binding of oxygen by haemoglobin in the pulmonary capillaries depend?
Answer:

The formation of oxyhaemoglobin depends on the following factors—

1. High PO₂ in alveolus
2. Low PCQ2 in alveolus, 0 high pH of blood,
3. Low temperature of lungs.

Question 10. Under what conditions, does dissociation of oxyhaemoglobin in the capillaries of various organs occur fast?
Answer:

In the human body, oxyhaemoglobin dissociates to produce oxygen in the capillaries of various organs other than the lungs.

This oxygen diffuses to associated tissues and is used in cellular respiration. The conditions required for oxyhaemoglobin are—

• Low pO₂ in tissues,
• High pcO₂ ‘n tissues,
• Low pH in the blood,

Increase in temperature in tissues.

Question 11. Oxygen transport capacity in healthy individuals is 20 volume per cent- what does this mean?
Answer:

Oxygen transport capacity in healthy individuals is 20 volume per cent

In a healthy individual, lg haemoglobin transports 1.34 ml O₂. 100 ml blood of a healthy individual contains 15 g of haemoglobin.

That means, in 100 ml blood, approximately 1.34 X 15 = 20.1 = 20 ml O₂ is transported, when it is 100% saturated. So, the oxygen transport capacity in a healthy individual is called ’20 volume per cent’.

Class 11 biology breathing and exchange of gases Q&A

Question 12. What is carboxyhaemoglobin? On what condition does the compound formation take place?
Answer:

Carboxyhaemoglobin

Carbon dioxide present in the blood capillaries in different organs of the human body reacts with the haemoglobin of RBCs, to form an unstable compound which is called carboxyhaemoglobin.

The conditions necessary for the formation of this compound are—

1. high P
2. low PO₂ in tissues.

Question 13. Where is carbonic anhydrase (CA) found? Write its functions.
Answer:

Carbonic anhydrase (CA) is a fast-acting enzyme. It is present in huge quantities in RBCs but less in blood plasma.

Due to the activity of CA, carbonic acid (H2C03) forms in RBCs by the reaction of carbon dioxide and water. Next, it dissociates H2C03 in HC03- and H+ and carries out the reverse reaction. CO₂ + H20 H2C03 HCO- + H+

Question 14. Write the names of the region in the brain that regulates respiration. Write the respiratory centres located in that region.
Answer:

The region of the brain that regulates respiration is—

1. Medulla oblongata,
2. Pons varolii.

The centres located in the medulla oblongata are the dorsal regulatory group and the ventral regulatory group.

The centres located in Pons Varolii are-

1. Pneumotaxic centre and
2. Apneustic centre.

Question 15. Name two chemical stimuli that regulate breathing, Name two chemical receptors that regulate breathing.
Answer:

Two chemical stimuli controlling breathing are—

More carbon dioxide concentration in blood and H+ ion concentration in blood.

Two chemical receptors that regulate breathing are—

The region near the medulla oblongata in the brain and wall of the aortic arch and carotid artery.

Question 16. What is the reason behind respiratory trouble in premature babies? Answer: Generally, after the formation of the human embryo, surfactant formation in the alveoli occurs in the 35th week.

So premature children, born before the 35th week, lack surfactant. In the absence of surfactant, alveoli shrink and gaseous exchange is hampered. As a result, children suffer from breathing trouble.

This type of disease in newborn babies is known as respiratory disease syndrome or RDS.

Class 11 Biology WBCHSE Breathing And Exchange Of Gases Very Short Answer Type Questions

Question 1. State the chemical reaction for bicarbonate ion and hydrogen ion becoming carbon dioxide in the lungs.
Answer:

\(\mathrm{HCO}_3^{-}+\mathrm{H}^{+} \rightarrow \mathrm{H}_2 \mathrm{CO}_3 \stackrel{\begin{array}{c}
\text { Carbonic } \\
\text { Anhydrase }
\end{array}}{\longrightarrow} \mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2\)

Question 2. A fluid-filled double membranous layer surrounds
Answer: Pleura

Question 3. What is the site of gaseous exchange in insects?
Answer: The site of gaseous exchange in insects is the trachea.

Question 4. Cigarette smoking causes emphysema. Give reason.
Answer: Cigarette smoking releases proteolytic enzymes in the lungs that damage the wall of the lungs and ultimately collapse of alveoli.

Breathing and exchange of gases chapter-wise questions with solutions

Question 5. What is the amount of O₂ supplied to tissues through every 100 ml of oxygenated blood under normal physiological conditions?
Answer: 5. 4.5 ml

Question 6. What is the condition called when the pleura of a lung is punctured?
Answer: Pneumothorax.

Question 7. A major percentage (97%) of O₂ is transported by RBCs in the blood. How does the remaining percentage (3%) of O₂ transport?
Answer: The remaining percentage of O₂ is transported as a physical solution i.e. dissolved in the plasma of blood.

Question 8. What is vital capacity?
Answer:

Vital capacity:

The maximum volume of air that can be exhaled after a maximal inspiration is called vital capacity.

Question 9. What is the conducting zone?
Answer:

Conducting zone

The conducting zone extends from the top of the trachea to the beginning of the respiratory bronchioles and no gas exchange occurs due to the absence of alveoli.

Short answer questions on breathing and exchange of gases

Question 10. Define residual volume. Or, State the volume of air remaining in the lungs after normal breathing.
Answer:

Residual volume

Residual volume is the amount of air remaining in the lungs after a maximal exhalation.

Question 11. Name the smallest airways in the conducting zone.
Answer: Terminal bronchioles.

Question 12. Why is it more difficult to breathe in when the stomach is full?
Answer: A full stomach impedes the downward motion of the contracting diaphragm. As a result, breathing becomes difficult

Question 13. Which component of the respiratory system helps in the generation of pressure gradient for breathing?
Answer: Diaphragm and intercostal muscles in ribs.

Question 14. How is the bulk of carbon dioxide carried in blood?
Answer: The bulk of carbon dioxide in blood is carried as bicarbonate compounds.