Lesson 3 of 11 · 6 min
Steps of respiration
NCERT §14.1.1
One O2 molecule Meher breathes in during warm-up will pass through five separate steps before her calf muscle can use it. Miss one and the chain breaks.
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In short
Breathing or pulmonary ventilation: atmospheric air is drawn in and CO₂-rich alveolar air is released.
Diffusion of O₂ and CO₂ across the alveolar membrane.
Transport of the gases by the blood.
Diffusion of O₂ and CO₂ between the blood and the tissues.
Use of O₂ by cells for catabolic reactions, with release of CO₂; this last step is cellular respiration, dealt with in Chapter 12 (Respiration in Plants).