NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases: As you may have studied earlier, oxygen () is utilized by the organisms by (indirectly) break down of simple molecules like glucose, amino acids, fatty acids, etc., so that energy can be derived to perform various activities. Carbon dioxide ( ) is among those gases which is harmful, and in the solutions of NCERT class 11 biology chapter 17 breathing and exchange of gases you will get questions and solutions related to these topics. You will study that their is a process of exchange of from the atmosphere with produced by the cells which is called breathing and commonly it is known as respiration. Wait simply place your hands on your chest; you can feel a slight motion in the chest moving towards up and down. You know that it is due to breathing. How do we breathe? The answer is with the help of respiratory organs and the mechanisms of breathing are the most important one as in NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases you get questions related to this. If you are looking for an answer from any other chapter even from any other class then go with NCERT Solutions, there you will get all the answers.
Here are the important topics of CBSE NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases mentioned below:
17.1 Respiratory Organs
17.1.1 Human Respiratory System
17.2 Mechanism of Breathing
17.2.1 Respiratory Volumes and Capacities
17.3 Exchange of Gases
17.4 Transport of Gases
17.4.1 Transport of Oxygen
17.4.2 Transport of Carbon dioxide
17.5 Regulation of Respiration
17.6 Disorders of Respiratory System
You will study that inspiration and expiration are carried out by creating pressure gradients between the atmosphere and the alveoli with the help of specialized muscles, that are: intercostals and diaphragm. You will also learn that respiratory rhythm is being maintained by the respiratory centre which is located in the medulla region of our brain. In NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases, you will get questions all related to our breathing, exchange of gases and their machanisms.
After going through the solutions of NCERT class 11 biology chapter 17 breathing and exchange of gases, you must be able to understand the answers of all the following questions:
NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases- Solved Exercise Questions-
Q1. Define vital capacity. What is its significance?
Vital capacity refers to the maximum volume of air that can be exhaled after a maximum inspiration. It is about 3.5 — 4.5 liters in the human body.
It promotes the act of supplying fresh air and getting rid of foul air, thereby increasing the gaseous exchange between the tissues and the environment.
Q2. State the volume of air remaining in the lungs after a normal breathing.
The volume of air remaining in the lungs after normal breathing is called functional residual capacity (FRC). It combines expiratory reserve volume (ERV) and residual volume (RV). ERV is the maximum volume of air that can be exhaled after a normal expiration and it is about 1000 mL to 1500 mL. RV, on the other hand, refers to the volume of air remaining in the lungs after maximum expiration and is about 1100 mL to 1500 mL.
Thus, FRC = ERV + RV
1500 + 1500 = 3000 mL
Hence, functional residual capacity of the human lungs is about 2500 - 3000 mL.
Q4. What are the major transport mechanisms for CO_2? Explain.
The major transport mechanisms for CO2 is transported by sodium bicarbonate as well as red blood cells. See, about 70% of carbon dioxide is transported as sodium bicarbonate. As CO2 diffuses into the blood plasma, a large part of it combines with water to form carbonic acid in the presence of the enzyme carbonic anhydrase. Carbonic anhydrase is a zinc enzyme that speeds up the formation of carbonic acid. This carbonic acid dissociates into bicarbonate (HCO3–) and hydrogen ions (H+). About 20 – 25% of CO2 is transported by the red blood cells as carbaminohaemoglobin. Carbon dioxide binds to the amino groups on the polypeptide chains of hemoglobin and forms a compound known as carbaminohaemoglobin.
Q5. What will be the pO_2 and pCO_2in the atmospheric air compared to those in the alveolar air?
(i) lesser, higher
(ii) higher, lesser
(iii) higher, higher
(iv) lesser, lesser
PO2 higher, pCO2 lesser
As the partial pressure of oxygen in atmospheric air is higher than that of oxygen in alveolar air. So, in atmospheric air, pO2 is about 159 mm Hg and in alveolar air, it is about 104 mm Hg. The partial pressure of carbon dioxide in atmospheric air is lesser than that of carbon dioxide in alveolar air.
In atmospheric air, pCO2 is about 0.3 mmHg and in alveolar air, it is about 40 mm Hg.
Q6. Explain the process of inspiration under normal conditions.
Inspiration is the process, during which atmospheric air is drawn inside the body. It can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure.
It is initiated by the contraction of diaphragm which increases the volume of the thoracic chamber in the anteroposterior axis. The contraction of external intercostal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs,
Q7. How is respiration regulated?
A center present in the medulla region of the brain called respiratory rhythm center and it is primarily responsible for respiration regulation. And another center which is present in the pons region of the brain called pneumotaxic center. It can moderate the functions of the respiratory rhythm center. The neural signal from this center can reduce the duration of inspiration and thereby alter the respiratory rate.
A chemosensitive area is situated adjacent to the rhythm center which is highly sensitive to CO 2 and hydrogen ions. Increase in these substances can activate this center, which in turn can signal the rhythm center to make necessary adjustments in the respiratory process by which these substances can be eliminated. Receptors associated with aortic arch and carotid artery also can recognize changes in CO 2 and H + concentration and send necessary signals to the rhythm center for remedial actions. The role of oxygen in the regulation of respiratory rhythm is quite insignificant.
NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases:
Q8. What is the effect of pCO_2 on oxygen transport?
Breathing and exchange of gases chapter will tell you that pCO_2 plays an important role in the transportation of oxygen. The low pCO_2 and high pO_2 favors the formation of oxyhaemoglobin take place at alveolus. And at the tissues, the high pCO_2 and low pO_2 favor the dissociation of oxygen from oxyhaemoglobin. So, the affinity of haemoglobin for oxygen is enhanced by the decrease of pCO_2 in blood. Therefore, oxygen is transported in the blood as oxyhaemoglobin and oxygen dissociate from it at the tissues.
Q9. What happens to the respiratory process in a man going up a hill?
When a man goes uphill, he gets less oxygen with each breath and as we know that when altitude increases, the oxygen level in the atmosphere decreases.
Because of this, the amount of oxygen in the blood start to decline. The respiratory rate increases in the response to the decrease in the oxygen content of the blood. Simultaneously, the rate of heartbeat increases to increase the supply of oxygen to the blood.
Q10. What is the site of gaseous exchange in an insect?
In insects, gaseous exchange takes place through a network of tubes collectively known as the tracheal system. The small openings on the sides of an insect’s body are called spiracles and oxygen-rich air enters through the spiracles. These spiracles are connected to the network of tubes. From the spiracles, oxygen enters the tracheae and from here, oxygen diffuses into the cells of the body. The movement of carbon dioxide follows the reverse path and the CO2 from the cells of the body first enters the tracheae and then leaves the body through the spiracles.
Q11. Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
The oxygen dissociation curve is a graph which shows the percentage of saturation of oxyhaemoglobin at various partial pressures of oxygen. This curve shows the equilibrium of oxyhaemoglobin and haemoglobin at various partial pressures. In the case of the lungs, the partial pressure of oxygen is high. So, haemoglobin binds to oxygen and forms oxyhaemoglobin.
Solutions for NCERT class 11 biology chapter 17 breathing and exchange of gases:
Q12. Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.
Hypoxia is a type of condition characterized by an inadequate or decreased supply of oxygen to the lungs. It is caused by several extrinsic factors such as a reduction in pO_2, inadequate oxygen, etc. It can be also classified as either generalized, affecting the whole body, or local, affecting a region of the body.
Different types of hypoxia are:
- Anaemic hypoxia
- Hypoxemic hypoxia
Q13. (a) Distinguish between IRV and ERV
Difference between the IRV and ERV are given below:
- Total lung capacity minus the volume of air in the lung at the end of a normal inspiration. This means that we have a reserve volume that we can tap into as tidal volume increases with exercise or activity.
- IRV is about 2500 – 3500 mL in the human lungs.
- Difference between the volume of air left in the lung at the conclusion of normal expiration versus at the conclusion of maximal expiration. That means that we have a "reserve" volume which we can tap into when our tidal volume increases with exercise or activity.
- ERV is about 1000 – 1500 mL in the human lungs.
Q13. (b) Distinguish betweenInspiratory capacity and Expiratory capacity.
Difference between Inspiratory capacity and Expiratory capacity:
- It is the volume of air that can be inhaled after a normal expiration.
- IC = TV + IRV
- It is the volume of air that can be exhaled after a normal inspiration.
- EC = TV + ERV
CBSE NCERT solutions for class 11 biology chapter 17 breathing and exchange of gases:
Q13 (c).Distinguish between Vital capacity and Total lung capacity.
- It is the maximum volume of air that can be exhaled after a maximum inspiration. It includes IC and ERV.
- It is about 4000 mL in the human lungs.
Total lung capacity
- It is the volume of air in the lungs after a maximum inspiration. It includes IC, ERV, and residual volume.
- It is about 5000-6000 mL in the human lungs.
Q14 What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.
Tidal volume is the volume of air that is transported into and out of the lungs (inspired or expired) with each normal respiratory cycle. Tidal volume is approximately 6000 to 8000 mL of air per minute for a healthy human.
We can calculate the hourly tidal volume for a healthy human.
If, Tidal volume = 6000 to 8000 mL/minute
So, the Tidal volume in an hour will be:
= 6000 to 8000 mL × (60 min)
= 3.6 × 105 mL to 4.8 × 105 mL
Hence, the hourly tidal volume for a healthy human is approximately 360000 ml-480000 ml.
If you are facing any issue in understanding these answers of above questions, then don't worry again go through that NCERT Book and try to understand all the concepts of every topic and then write the answers of all these questions by your own and then compare them with solutions for NCERT class 11 biology chapter 17 breathing and exchange of gases. You will see that your knowledge, as well as the understanding of these concepts will increase and you will be able to explain the answers in a more better way.
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