Oxygen transport 1

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Oxygen transport 1

• How haemoglobin carries oxygen

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Oxygen transport

• Haemoglobin is a conjugated protein attached to a
  prosthetic group
• The prosthetic group is called haem and contains
  iron
• There are four haem groups in each haemoglobin
  molecule each of which can bind to an oxygen
  molecule.

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Oxygen transport
in lungs

• Hb 4O2 HbO8
• haemoglobin oxygen oxyhaemoglobin

in tissues
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Oxygen transport

• The partial pressure of oxygen (pO2) is a measure
  of the amount of oxygen concentration
• The greater the concentration of dissolved
  oxygen, the higher its partial pressure

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Oxygen transport

• RBC pick up oxygen in the capillaries that cover
  the alveoli of the lungs
• Here the partial pressure of oxygen is high and
  the haemoglobin becomes saturated with oxygen.

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Oxygen transport

• The rbc carry the oxyhaemoglobin to respiring
  tissues.
• Here the partial pressure of oxygen is low as the
  oxygen is being used up in respiration.
• Under these conditions, oxyhaemoglobin gives up
  its oxygen to the respiring cells.

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Oxygen transport
We say that the oxygen dissociates.
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Oxygen transport

• Haemoglobin
• In high concentrations of oxygen it will combine
  with large amounts of the gas.
• In low concentrations it dissociates with the
  gas, giving it up.

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Oxygen transport

• Samples of haemoglobin can be exposed to
  different partial pressures of oxygen
• The amount of oxygen combining at the different
  partial pressures can then be estimated
• The percentage saturation of each sample can then
  be plotted against the partial pressure to give
  and oxygen dissociation curve.

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pO2 in human lung alveoli
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pO2 in human lung alveoli
pO2 in human muscle capillaries
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Oxygen transport

• Look at the graph
• Hb becomes almost fully saturated with oxygen at
  high partial pressures such as is found in the
  lungs
• Oxyhaemoglobin dissociates under low partia
  pressures such as found in respiring tissue.

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Oxygen transport

• Why is the curve S shaped?
• Each molecule of Hb has four haem groups
• When the first oxygen combines with the first
  haem group the shape of the Hb molecule becomes
  distorted
• This makes it easier for the other three oxygen
  molecules to bind to the other haem groups