Question

Topic 9: Oxygen-hemoglobin dissociation curve

Define what the oxygen hemoglobin dissociation curve is and describe why it is physiologically important. explain the significance of the sigmoidal shape, including the physiological significance of the plateau and step portions, and the relationship between oxygen loading/unloading with changes to po2

Give an example of a situation/condition that would result in a right shift of the oxygen hemoglobin dissociation curve. explain what causes the shift and relate it to oxygen binding affinity, loading-unloading of oxygen, and changes in po2

Answer 1

Oxygen dissociation curve is defined as the curve which shows the percentage saturation of hemoglobin with the oxygen. We can see that there is a sigmoid curve. A molecule of hemoglobin can carry 4 molecules of oxygen. In it the binding of the first molecule is so faster and then the bind of second molecule is slower than the first. So the 50% saturation occurs so fast. The binding of 3rd molecule makes around 75% saturation and is do slow and atlast the binding of the fourth molecule is makes the plateau phase and makes a sigmoid curve. The pateu phase means that no more oxygen bcan bind to the hemoglobin even if the level of oxygen increases.

Hemoglobin is more in affinity towards Carbon dioxide than oxygen. So when there is more carbon dioxide the oxygen detaches from the hemoglobin making the unloading. If po2 is more then hemoglobin binds to oxygen faster makes the loading.

When the presence of Carbon-dioxide is more the curve shift towards right showing less affinity of hemoglobin towards oxygen. Because the binding of oxygen decreases in presence of carbon dioxide. This happens at the time of exercise as more Carbon-dioxide bis present in blood and the pH is less. Thus the loading of oxygen decreases bas po2 is less and the unloading is initiated more.