Carriage of Oxygen
- Created by: Eleanor Izzard
- Created on: 30-12-12 12:33
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- Carriage of Oxygen
- Haemoglobin
- +oxygen ---> oxy-haemoglobin
- oxy-haemoglobin must be able to dissociate with oxygen to release it into respiring cells
- complex protein with 4 sub-units consisting of a polypetide chain and a haem group
- each haem group contains an iron ion (2+) that can attract and hold an oxygen molecule - has an affinity for it
- +oxygen ---> oxy-haemoglobin
- Oxygen Transport
- amount of oxygen is measured by the relative pressure that it contributes to a mixture of gases - PARTIAL PRESSURE/ pO2/OXYGEN TENSION - measured in kPa
- oxy-haemoglobin dissociation curve - S shape
- at low oxygen tensions, the haemoglobin does not readily take up oxygen molecules because the haem groups that attract the oxygen are in the centre of the molecule
- accounts for the low saturation level of haemoglobin at low oxygen tensions
- as oxygen tension rises, the diffusion gradient into the haemoglobin molecule increases, so one oxygen molecule diffuses into the haemoglobin molecule, causing a conformational change in the shape
- allows more oxygen molecules to diffuse into the haemoglobin
- accounts for the steepness of the curve as the oxygen tension rises
- allows more oxygen molecules to diffuse into the haemoglobin
- once the haemoglobin contains 3 oxygen molecules, it becomes more difficult for the 4th to diffuse in - so it is difficult to achieve 100% oxygen saturation
- at low oxygen tensions, the haemoglobin does not readily take up oxygen molecules because the haem groups that attract the oxygen are in the centre of the molecule
- Fetal Haemoglobin
- has a higher affinity for oxygen than adult haemoglobin
- must be able to pick up oxygen when adult haemoglobin releases it
- must absorb oxygen from the mothers blood, reducing the oxygen tension within the blood fluid, making the maternal haemoglobin release oxygen
- so the fetal dissociation curve is to the left of the adults
- Haemoglobin
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