मराठी

Transport of Gases

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Estimated time: 5 minutes
CBSE: Class 12

Key Points: Transport of Gases

  • O₂ transport - 97% by RBCs (as oxyhaemoglobin) and 3% dissolved in plasma. CO₂ transport - 20-25% by RBCs (as carbaminohaemoglobin), 70% as bicarbonate, and 7% dissolved in plasma.
  • Haemoglobin is a red-coloured, iron-containing pigment in RBCs. Each haemoglobin molecule can carry 4 molecules of O₂.
  • The Oxygen Dissociation Curve is a sigmoid curve plotting % saturation of haemoglobin with O₂ against pO₂.
  • In alveoli - high pO₂, low pCO₂, low H⁺, lower temperature → favourable for oxyhaemoglobin formation. In tissues - low pO₂, high pCO₂, high H⁺, higher temperature → favourable for dissociation of O₂ from oxyhaemoglobin.
  • Every 100 mL of oxygenated blood delivers 5 mL of O₂ to tissues; every 100 mL of deoxygenated blood delivers 4 mL of CO₂ to alveoli.
  • Carbonic anhydrase enzyme (present in RBCs) facilitates: CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ in tissues. This reaction reverses in alveoli (low pCO₂), releasing CO₂.
  • High pCO₂ and low pO₂ in tissues promote CO₂ binding to haemoglobin; low pCO₂ and high pO₂ in alveoli promote dissociation of CO₂ from carbaminohaemoglobin.
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