Below are two oxygen dissociation curves. The one on the left illustrates oxygen

Question

Below are two oxygen dissociation curves. The one on the left illustrates oxygen dissociation curve for hemoglobin that exhibits cooperativity. The one on the right shows what the oxygen dissociation curve for an imaginary hemoglobin that DOES NOT bind O2 in a cooperative manner (in other words, the subunits do not influence each other binding). Complete the series of questions below using the information in these two graphs.

Question 10.5 pts

The percent O2 saturation in the lungs under noncooperative binding is                           [ Select ]                       ["50", "100", "20", "80"]         , and the percent O2 saturation in the lungs under cooperative binding is                            [ Select ]                       ["80", "100", "50", "20"]         .

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Question 20.5 pts

The percent O2 saturation in tissues at rest under noncooperative binding is                           [ Select ]                       ["10", "30", "50", "70"]         , and the percent O2 saturation in tissues at rest under cooperative binding is                            [ Select ]                       ["50", "70", "20", "10"]         .

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Question 30.5 pts

The percentage of O2 DELIVERED to tissues at rest under noncooperative binding is                           [ Select ]                       ["10", "30", "50", "70"]         , and the percentage of O2 DELIVERED to tissues at rest under cooperative binding is                            [ Select ]                       ["10", "70", "50", "30"]         .

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Question 40.5 pts

The percentage of O2 is DELIVERED to exercising tissues under under non-cooperative binding is                            [ Select ]                       ["10", "70", "50", "80"]         , and the percentage of O2 is DELIVERED to exercising tissues under cooperative binding is                            [ Select ]                       ["70", "50", "10", "80"]         .

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Question 50.5 pts

Based on what you have learned from the comparison above, what is the major distinction between the noncooperative binding and the cooperative binding? How does this relate to/impact gas exchange?

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The x-axis shows the partial pressure of oxygen (PO2). This is a measure of the amount of oxygen present in a tissue. The blue arrows on thexaxis show the partial pressure of oxygen in various tissues of the body. The y axis shows the oxygen saturation of hemoglobin (o2 saturation). This is the percentage of oxygen-binding sites on hemoglobin molecules that are actually bound to oxygen. Noncooperative binding Cooperative binding 100 100 80 80 60 60 o 40 o 40 20 20 10 20 30 40 50 (60 70 80 90 100 10 20 30 40 50 60 70 80 90 100 tissue during tissue lungs tissue during tissue lungs at rest at rest exercise exercise PO2 (mm Hg) PO2 (mm Hg)

Explanation / Answer

From the graph , the percent saturation of hemoglobin expresses average saturation of hemoglobin with oxygen

1) percent oxygen saturation in lungs

Cooperative binding = 100%

Non cooperative binding =100%

2 ) percent oxygen saturation in tissue at rest

Cooperative binding = 50%

Noncooperative binding = 70%

3) percentage of oxygen delivered in tissue at rest

Cooperative binding = 50%

Noncooperative binding = 30%

4) percentage of oxygen delivered in exercising tissue

Cooperative binding = 80%

Noncooperative binding = 50 %

5) Cooperative binding show a sigmoidal curve whereas noncooperative binding show a hyperbolic curve. A quaternary structure of hemoglobin has affinity for oxygen. Cooperative binding means binding of ligand to the one site of macromolecule influence the binding of ligand to another site means there is a interaction between binding site where as when binding of ligand for example oxygen to hemoglobin has no influence on the binding of additional oxygen molecule to the same hemoglobin called non cooperativity. The degree of cooperativity in the binding reaction is expressed by the Hill coefficient (n). Here, in this Cooperative curve n>1 where as for non cooperativity curve n=1.

Cooperative binding help in a distribution of oxygen throughout the body according to need . For example, in this graph cooperativity shows oxygen distribution different in exercising and resting tissue because exercising tissue require more oxygen but non cooperativity shows equal distribution of oxygen in both case.

When higher amount of oxygen is present, it overcome the inhibitory T state means deoxyhemoglobin less affinity for oxygen. During oxygen binding to one subunit, T state convert to R state means oxyhemoglobin higher affinity for oxygen state, this oxygen binding dissociate proton from haemoglobin subunit that help in exhalation of carbon dioxide. Cooperativity permits the loading and unloading of the large amount of the oxygen at physiological relevant pressure. Due to this phenomenon , hemoglobin increase affinity for oxygen so it fully saturated and distribute oxygen all our the body.

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