Carriage of oxygen

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Last updated 6:54 PM on 6/1/26
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10 Terms

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Must know facts about erythrocytes (RBC)

  • Biconcave for greater surface area

  • Made in bone marrow

  • Mature erythrocytes have no nucleus

  • Only live for about 120 days

  • 1mm3 of blood contains 5 million erythrocytes

  • Haemoglobin red pigment contains iron

  • 300 million haemoglobin molecules in one erythrocyte

  • Haemoglobin carries oxygen

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Describe the transport of oxygen

  • Oxygen binds to haemoglobin in RBC to form oxyhaemoglobin. One molecule of haemoglobin can carry four oxygen molecules.

  • At lungs O2 concentrations are high so it diffuses into erythrocytes and binds to haemoglobin. At tissues, O2 concentrations are low so diffuses from erythrocytes into body cells down conc. gradient

Note:

When all of haemoglobins oxygen binding sites are all taken up with oxygen it is saturated

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What is meant by the term dissociation

Release of oxygen from haemoglobin

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What is meant by the term of affinity

Attraction for (oxygen)

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What is meant by the term partial pressure

The pressure that oxygen exerts within a mixture of gases

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Oxygen dissociation curve

  • At high partial pressures of oxygen, haemoglobin will have a higher affinity for oxygen so it binds more easily but dissociates slowly and if partial pressures of oxygen is low haemoglobin has low affinity it binds slowly and dissociates easily.

<ul><li><p>At high partial pressures of oxygen, haemoglobin will have a higher affinity for oxygen so it binds more easily but dissociates slowly and if partial pressures of oxygen is low haemoglobin has low affinity it binds slowly and dissociates easily.</p></li></ul><p></p>
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Why is the oxygen dissociation curve sigmodial shaped

This is due to haemoglobins affinity at different partial pressures of oxygen and the ease of binding.

  • The first O2 molecule is difficult to bind due to the shape of haemoglobin which is why curve shallow at start

  • Second and third O2 bind easier ,explaining the steeper part of curve in the middle, as haemoglobin undergoes confrontational change once first O2 is bound. This is called positive co-operation

  • Fourth O2 molecule difficult to bind due to crowding and the tendency for O2 to dissociate, explaining the levelling of the curve at the top

<p>This is due to haemoglobins affinity at different partial pressures of oxygen and the ease of binding.</p><p></p><ul><li><p>The first O<sub>2 </sub>molecule is difficult to bind due to the shape of haemoglobin which is why curve shallow at start</p></li><li><p>Second and third O<sub>2</sub> bind easier ,explaining the steeper part of curve in the middle, as haemoglobin undergoes confrontational change once first O<sub>2</sub> is bound. This is called positive co-operation</p></li><li><p>Fourth O<sub>2</sub> molecule difficult to bind due to crowding and the tendency for O<sub>2 </sub> to dissociate, explaining the levelling of the curve at the top</p></li></ul><p></p>
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What is foetal haemoglobin

Foetal haemoglobin has a higher affinity for oxygen at the same partial pressures of oxygen this means that as maternal blood passes foetus it diffuses from blood to bind with foetal haemoglobin. At lower pO2 higher saturation of foetal haemoglobin.

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How is fetal haemoglobin different on a dissociation curve

The foetal haemoglobin curve shifts to the left

<p>The foetal haemoglobin curve shifts to the left</p>
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What is myoglobin

Similar structure to haemoglobin but is just one polypeptide chain. Stores oxygen in muscles. Has a higher affinity for oxygen meaning it can hold oxygen until muscles really need it.