NCERT Solutions for Class 11 Biology Chapter 17

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Breathing and Exchange of Gases: Solutions




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NCERT Solutions for Class 11 Biology Chapter 17 Breathing and Exchange of Gases
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Important Notes on Breathing and Exchange of Gases

  • Breathing (External respiration): The process of exchange of O2 from the atmosphere with CO2 produced by the cells.
  • Carbamino haemoglobin: Compound formed in RBCs when CO2 combine with haemoglobin.
  • Inspiration: Oxygen from fresh air taken by lungs and diffuses into the blood.
  • Diaphragm: A muscular, membranous partition separating the thoracic cavity from the abdominal cavity.
  • Expiration: CO2 given up by venous blood in the lungs is sent out to exterior.
  • 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.
  • 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.
  • Pharynx: The tube or cavity which connects the mouth and nasal passages with oesophagus. It has three parts.
    1. Nasopharynx (anterior part)
    2. Oropharynx (middle part) and
    3. Laryngopharynx (posterior part which continues to larynx)
  • Adam’s Apple: The projection formed by the thyroid cartilage and surrounds the larynx at the front of the neck.
  • Tidal volume (TV): volume of air during normal respiration (500 mL)
  • Inspiratory Reserve Volume (IRV): Additional volume of air inspired by a forcible inspiration. 2500mL to 3000mL.
  • Expiratory Reserve Volume (ERV): Additional volume of air, a person can expire by a forcible expiration.



Inspiration
  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.