Describe the oxyhemoglobin dissociation curve in the following: explain why oxyg
ID: 3481468 • Letter: D
Question
Describe the oxyhemoglobin dissociation curve in the following:
explain why oxygen leaves hemoglobin in the tissues
I have the below info but need one paragraph in own words.
Reason for releasing of oxygen from Hb in tissues:
Each gram of hemoglobin can combine with 1.34 mL of oxygen.
At low partial pressures of oxygen (e.g. within tissues that are deprived of oxygen), oxyhemoglobin releases the oxygen to form hemoglobin.
The oxygen dissociation curve has a sigmoid shape because of the co-operative binding of oxygen to the 4 polypeptide chains of Hb. Hemoglobin is therefore most attracted to oxygen when 3 of the 4 polypeptide chains are bound to oxygen.
Explanation / Answer
Please find below explanation. Please let me know if you any more question regarding this.
The oxygen dissociation curve is a graph that plots the proportion of haemoglobin in its oxygen-laden saturated form on the vertical axis against the partial pressure of oxygen on the horizontal axis.
At high partial pressures of oxygen, haemoglobin binds to oxygen to form oxyhaemoglobin. All of the red blood cells are in the form of oxyhaemoglobin when the blood is fully saturated with oxygen. Each gram of haemoglobin can combine with 1.34 mL of oxygen. At low partial pressures of oxygen (e.g. within tissues that are deprived of oxygen), oxyhaemoglobin releases the oxygen to form haemoglobin.
The oxygen dissociation curve has a sigmoid shape because of the co-operative binding of oxygen to the 4 polypeptide chains. Co-operative binding means that haemoglobin has a greater ability to bind oxygen after a subunit has already bound oxygen. Haemoglobin is therefore most attracted to oxygen when 3 of the 4 polypeptide chains are bound to oxygen.
There is often a P50 value expressed on the curve, which is the value that tells us the partial pressure of oxygen at which the red blood cells are 50% saturated with oxygen. At an oxygen saturation of 50% the PaO2 is approximately 25 mmHg (3.5k Pa).
Factors affect the oxygen dissociation curve:
The oxygen dissociation curve can be shifted right or left by a variety of factors. A right shift indicates decreased oxygen affinity of haemoglobin allowing more oxygen to be available to the tissues. A left shift indicates increased oxygen affinity of haemoglobin allowing less oxygen to be available to the tissues.
Factor
Decrease
Increase
pH
Right shift
Left shift
CO2
Left shift
Right shift
Temperature
Left shift
Right shift
2,3-DPG
Left shift
Right shift
How does carbon monoxide affect the curve: Carbon monoxide (CO) interferes with the oxygen transport function of the blood by combining with haemoglobin to form carboxyhaemoglobin (COHb). CO has approximately 240 times the affinity for haemoglobin that oxygen does and for that reason even small amounts of CO can tie up a large proportion of the haemoglobin in the blood making it unavailable for oxygen carriage. If this happens the PO2 of the blood and haemoglobin concentration will be normal but the oxygen concentration will be grossly reduced. The presence of COHb also causes the oxygen dissociation curve to be shifted to the left, interfering with the unloading of oxygen.
How does methaemoglobin affect the curve: Methaemoglobin is an abnormal form of haemoglobin in which the normal ferrous form is converted to the ferric state. Methaemoglobinaemia causes a left shift in the curve as methaemoglobin does not unload oxygen from haemoglobin.
Factor
Decrease
Increase
pH
Right shift
Left shift
CO2
Left shift
Right shift
Temperature
Left shift
Right shift
2,3-DPG
Left shift
Right shift
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