NCERT Solutions for Class 11 Biology Chapter 17
NCERT Solutions for Class 11 Biology Chapter 17 Breathing and Exchange of Gases not only to Study online but also download in PDF format free updated for new academic session 2020-21.Download NCERT Solutions based on latest NCERT Books 2020-2021 for CBSE, UP Board, MP Board and all other boards who are using NCERT books 2020-2021 as course books. Download Offline Apps and Expression your views through Discussion Forum.
NCERT Solutions for Class 11 Biology Chapter 17
|Chapter 17:||Breathing and Exchange of Gases|
Class 11 Biology Chapter 17 Solutions in English
NCERT Solutions for Class 11 Biology Chapter 17 in PDF form free download or view online for new academic session 2020-21. Download NCERT Books 2020-21 and Offline Apps based on latest CBSE Syllabus. NCERT Solutions 2020-21 are helpful for NIOS Study also. If you have any doubt regarding to educational facts, please visit to discussion forum ask your questions.
Important Notes on Breathing and Exchange of Gases
1. Breathing (External respiration): The process of exchange of O2 from the atmosphere with CO2 produced by the cells.
2. Carbamino haemoglobin: Compound formed in RBCs when CO2 combine with haemoglobin.
3. Inspiration: Oxygen from fresh air taken by lungs and diffuses into the blood.
4. Diaphragm: A muscular, membranous partition separating the thoracic cavity from the abdominal cavity.
5. Expiration: CO2 given up by venous blood in the lungs is sent out to exterior.
6. Respiration: The sum total of physical and chemical processes by which oxygen and carbohydrates (main food nutrient) etc. are assimilated into the system and the oxidation products like carbon dioxide and water are given off.
HYPOXIA-SHORTAGE OF OXYGEN IN TISSUES.
1. Partial Pressure-The pressure contributed by an individual gas in a mixture of gases. It is represented as pO2 for oxygen and pCO2 for carbon dioxide.
2. Pharynx: The tube or cavity which connects the mouth and nasal passages with oesophagus. It has three parts.
i). Nasopharynx (anterior part)
ii). Oropharynx (middle part) and
iii). Laryngopharynx (posterior part which continues to larynx)
3. Adam’s Apple: The projection formed by the thyroid cartilage and surrounds the larynx at the front of the neck.
4. Tidal volume (TV): volume of air during normal respiration (500 mL)
5. Inspiratory Reserve Volume (IRV): Additional volume of air inspired by a forcible inspiration. 2500mL to 3000mL.
6. Expiratory Reserve Volume (ERV): Additional volume of air, a person can expire by a forcible expiration.
1. If the pressure within the lungs (intrapulmonary pressure) is less than the atmospheric pressure, i.e., there is negative pressure in the lungs with respect to the atmospheric pressure.
2. The contraction of diaphragm increases the volume of thoracic chamber in the antero-posterior axis.
3. The contraction of external intercoastals muscles lifts up the ribs and the sternum causing an increase in the volume of thoracic chamber in the dorso ventral axis.
4. It causes an increase in pulmonary volume decrease the intra-pulmonary pressure to less than the atmospheric pressure.
5. If forces the air out side to move in to the lungs, i.e., inspiration.
Important Questions on 11th Biology Chapter 17
∴ FRC = ERV + RV ≅ 1500 + 1500 ≅ 3000 mL
Functional residual capacity of the human lungs is about 2500 – 3000 mL.
Thus, the alveoli are the sites for gaseous exchange. The exchange of gases takes place by simple diffusion because of pressure or concentration differences. The barrier between the alveoli and the capillaries is thin and the diffusion of gases takes place from higher partial pressure to lower partial pressure. The venous blood that reaches the alveoli has lower partial pressure of O2 and higher partial pressure of CO2 as compared to alveolar air. Hence, oxygen diffuses into blood. Simultaneously, carbon dioxide diffuses out of blood and into the alveoli.
The volume of the thoracic chamber in the anteroposterior axis increases with the simultaneous contraction of the external intercostal muscles. This causes the ribs and the sternum to move out, thereby increasing the volume of the thoracic chamber in the dorsoventral axis. The overall increase in the thoracic volume leads to a similar increase in the pulmonary volume. Now, as a result of this increase, the intra-pulmonary pressure becomes lesser than the atmospheric pressure. This causes the air from outside the body to move into the lungs.
The chemosensitive region present near the respiratory centre is sensitive to carbon dioxide and hydrogen ions. This region then signals to change the rate of expiration for eliminating the compounds.
The receptors present in the carotid artery and aorta detect the levels of carbon dioxide and hydrogen ions in blood. As the level of carbon dioxide increases, the respiratory centre sends nerve impulses for the necessary changes.
The movement of carbon dioxide follows the reverse path. The CO2 from the cells of the body first enters the tracheae and then leaves the body through the spiracles.
The curve shows the equilibrium of oxyhaemoglobin and haemoglobin at various partial pressures.
In the lungs, the partial pressure of oxygen is high. Hence, haemoglobin binds to oxygen and forms oxyhaemoglobin.
Tissues have a low oxygen concentration. Therefore, at the tissues, oxyhaemoglobin releases oxygen to form haemoglobin.
The sigmoid shape of the dissociation curve is because of the binding of oxygen to haemoglobin. As the first oxygen molecule binds to haemoglobin, it increases the affinity for the second molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen.
In this condition, there is a reduction in the oxygen content of blood as a result of the low partial pressure of oxygen in the arterial blood.
In this condition, there is a reduction in the concentration of haemoglobin.
Stagnant or ischemic hypoxia
In this condition, there is a deficiency in the oxygen content of blood because of poor blood circulation. It occurs when a person is exposed to cold temperature for a prolonged period of time.
In this condition, tissues are unable to use oxygen. This occurs during carbon monoxide or cyanide poisoning.
It is about 6000 to 8000 mL of air per minute.
The hourly tidal volume for a healthy human can be calculated as:
Tidal volume = 6000 to 8000 mL/minute
Tidal volume in an hour
= 6000 to 8000 mL × (60 min)
= 3.6 × 105 mL to 4.8 × 10^5 mL
Therefore, the hourly tidal volume for a healthy human is approximately 3.6 × 10^5 mL to 4.8 × 10^5 mL.