What is the significance of the oxygen dissociation curve

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. The oxygen dissociation curve and the factors affecting it.

Which 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. A decrease in the pH shifts the curve to the right, while an increase in pH shifts the curve to the left.

This occurs because a higher hydrogen ion concentration causes an alteration in amino acid residues that stabilises deoxyhaemoglobin in a state the T state that has a lower affinity for oxygen. This rightward shift is referred to as the Bohr effect. A decrease in CO2 shifts the curve to the left, while an increase in CO2 shifts the curve to the right. CO2 affects the curve in two ways. Firstly, the accumulation of CO2 causes carbamino compounds to be generated, which bind to oxygen and form carbaminohaemoglobin.

Carbaminohaemoglobin stabilizes deoxyhaemoglobin in the T state. An increase in temperature shifts the curve to the right, whilst a decrease in temperature shifts the curve to the left. Increasing the temperature denatures the bond between oxygen and haemoglobin, which increases the amount of oxygen and haemoglobin and decreases the concentration of oxyhaemoglobin.

Temperature does not have a dramatic effect but the effects are noticeable in cases of hypothermia and hyperthermia. Carbon monoxide CO interferes with the oxygen transport function of the blood by combining with haemoglobin to form carboxyhaemoglobin COHb. CO has approximately times the affinity for haemoglobin than 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.

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. There are two other oxygen transport molecules that are required knowledge and commonly asked about in medical exams, fetal haemoglobin and myoglobin:. Fetal haemoglobin HbF is the main oxygen transport protein in the human fetus during the last 7 months of development. It persists in the newborn until roughly 6 months of age.

HbF has different globin chains to adult haemoglobin Hb. Whereas adult haemoglobin is composed of two alpha and two beta subunits, fetal haemoglobin is composed of two alpha and two gamma subunits.

This change in the globin chain results in a greater affinity for oxygen and allows the fetus to extract oxygen from the maternal circulation. This increased affinity for oxygen means that the oxygen dissociation curve for fetal haemoglobin is shifted to the left of that of adult haemoglobin.

The curve for myoglobin lies even further to the left than that of fetal haemoglobin and has a hyperbolic, not sigmoidal, shape. Myoglobin has a very high affinity for oxygen and acts as an oxygen storage molecule. It only releases oxygen when the partial pressure of oxygen has fallen considerably. The function of myoglobin is to provide additional oxygen to muscles during periods of anaerobic respiration.

Thank you to the joint editorial team of www. This information was broken down in the most simplest way possible to make it so easy to understand and teach to others. My tendency is to focus on and overemphasize certain areas that may be easy for me to understand, but overlook other factors that are as equally important to notice and cover as well.

How I wish this was how it was taught in Med school…but then again, I am older now, and can understand much better with a more mature level of understanding. Nevertheless, well explained!

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SOAP web service. Hemoglobin is composed of four subunits: two alpha subunits and two beta subunits, each of which contains a heme group and globin chain. The two states differ in their affinity to bind oxygen. In an unbound state, hemoglobin exists in the T state, and binding of oxygen occurs with low affinity. The T-state hemoglobin thus requires a higher partial pressure of oxygen pO2 to facilitate the binding of an oxygen molecule.

The binding of single oxygen induces a conformational change that destabilizes the T state and facilitates the transition of the other subunits to the high-affinity R state.

The binding of the first oxygen allows the second, third, and fourth oxygen molecules to subsequently bind with increasing ease. This relationship is an example of positive cooperativity. In a set of normal lungs, the partial pressure of oxygen is naturally high at the alveolar-capillary junction. Therefore, exposing the T state hemoglobin to vast amounts of oxygen and facilitating oxygen loading.

However, the partial pressure of oxygen is naturally lower in peripheral tissue, which aids in the release of oxygen. In the peripheral tissue, the T state of hemoglobin is preferred as there are a lower pO2 and less oxygen bound, which results in a quick release of the other three molecules of oxygen. Throughout the bloodstream, there are different pO2 levels that participate in a continuous equilibrating transition between T and R states.

The relationship between pO2 and SaO2 can be represented by the oxygen dissociation curve, which represents oxygen saturation y-axis as a function of the partial pressure of oxygen x-axis.

The sigmoid or S-shape of the curve is due to the positive cooperativity of hemoglobin. At this point, little additional binding occurs and the curve flattens out representing hemoglobin saturation. At the systemic capillaries, pO2 is lower and can result in large amounts of oxygen released by hemoglobin for metabolically active cells, which is represented by a steeper slope of the dissociation curve.

The strength by which oxygen binds to hemoglobin is affected by several factors and can be represented as a shift to the left or right in the oxygen dissociation curve. A rightward shift of the curve indicates that hemoglobin has a decreased affinity for oxygen, thus, oxygen actively unloads. A shift to the left indicates increased hemoglobin affinity for oxygen and an increased reluctance to release oxygen.

Several physiologic factors are responsible for shifting the curve left or right, such as pH, carbon dioxide CO2 , temperature, and 2,3-Disphosphoglycerate. A decrease in pH acidity shifts the dissociation curve to the right while an increase in pH alkalinity shifts the dissociation curve to the left. At greater concentrations of hydrogen ions, hemoglobin stabilizes in the deoxygenated T-state.