Question

An oxygen binding curve of fractional saturation versus pO₂ displays a sigmoidal shape. This is the oxygen binding curve for

Select one:

a. myoglobin in the presence of 2,3-BPG.

b. hemoglobin in the presence of 2,3-BPG.

c. myoglobin.

d. hemoglobin that has been dissociated into individual subunits.

Answer 1

The correct answer for this question is B. Basically when you plot the same graph for myoglobin, you will get a hyperbolic curve rather than sigmoidal curve ( S shape ) graph . This Sigmoidal shape graph in case of hemoglobin enables it to deliver much more oxygen to the tissues when compared with hyperbolic curve of myoglobin and this is the reason why myoglobin is not used as an oxygen transporter in the blood. Secondly 2-3,BPG is a compound which decreases the oxygen binding capability of the hemoglobin.

So there is a slight shift in the sigmoidal curve when you plot it for pure hemoglobin and hemoglobin in the presence of BPG,but for both the cases you do get a Sigmoidal (S shape ) curve. Hence option B is correct.