Transport of respiratory gases (D6)

• Haemoglobin can effectively transport O2 by binding to O2 in the lungs & dissociating O2 to the body cells. But how does the protein know when to bind/ let go? At high partial pressure of O2, haemoglobin has high affinity & ∴ binds to O2. At low partial pressure of O2, haemoglobin has low affinity & ∴ O2 is released.
• Exercise causes an ↑ rate of cellular respiration as muscles are more active → ↑ prod of CO2. Majority of CO2 produced by the body is converted to the more soluble & less toxic HCO3- ion. This occurs inside red blood cells & is catalysed by the enzyme carbonic anhydrase. Note that H ion ↓ pH of blood.
• How ventilation is controlled:

  Chemoreceptors in the carotid artery & the aorta send a message to the breathing centre in the medulla oblongata when a ↓ in pH is detected. Nerve impulses are then sent from medulla to the diaphragm & intercostal muscles, causing them to ↑ ventilation rate → ↑ rate of GE to remove CO2.
• ↑ metabolism → ↑ release of CO2 into the blood → ↓ pH of the blood → rightward shift of O2 dissociation curve → ↓ affinity of haemoglobin for O2. This aka Bohr shift. This ensures that respiring tissues have enuff O2 when their need for O2 is greatest.
• Both fetal haemoglobin & myoglobin (muscle haemoglobin) need to take O2 from adult haemoglobin ∴, adult haemoglobin will dissociate its O2 during low partial pressure of O2 where tissues are actively respiring/ in the placenta.
• Myoglobin:


  • Single heme–globin unit
  • Dissociation curve left of normal haemoglobin
  • Has higher affinity than normal haemoglobin
  • Func to obtain O2 from normal hemoglobin to store O2 in muscles
• Fetal haemoglobin:


  • 4 heme–globin unit (BUT not the same as adult)
  • Dissociation curve left of normal haemoglobin
  • Has higher affinity than normal haemoglobin
  • Function to obtain O2 from mother’s blood at placenta to supply the baby
• High altitude GE:

  Benefits:

  ↑ performance & endurance when returning at ↓ altitude due to ↑ conc of red blood cells & haemoglobin → ↑ O2 transported & hence ↑ lung efficiency & GE.

  Risks:

  Diseases such as altitude sickness, stroke & ↓ immunity sometimes occur. The ↑ stress on body ↑ muscle tissue breakdown. The efx are not permanent & ∴ extended training at high altitude is req. Lastly, may be unfair to competitors who cannot train at high altitude.