Oxygen affinity question

The affinity of oxygen for hemoglobin is:


Hello, is the answer A?

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Yes, it is A, I think the phrasing is a bit ambiguous though

Yeah I was confused with B at first, but this Q seems to mean that the concentration of oxygen (O2) in the surrounding environment is already high enough so hemoglobin has a higher affinity for oxygen. So, for instance, hemoglobin is more likely to bind with oxygen molecules in the lungs, where the oxygen concentration is high, and carry oxygen to tissues where it is needed for cellular respiration.

Conversely, when the concentration of oxygen in the environment is low, such as in peripheral tissues where oxygen is being released from hemoglobin to supply cells, hemoglobin’s affinity for oxygen decreases. This allows oxygen to be more readily released from hemoglobin and delivered to cells for metabolism.


This question has been formulated in an uncommon way (wired). Normally we say the affinity of hemoglobin for oxygen, or oxygen affinity of hemoglobin, or hemoglobin oxygen affinity.

Irrespective of which, the main reason for higher affinity is, as soon as one oxygen molecule binds to the iron in one heme-group, it stimulates binding of three other oxygen molecules to the other three heme groups of the hemoglobin molecule, a process called positive feed forward. So, the affinity for the first oxygen is very important.

It is also important to note that this process is not dependent only to the concentration of oxygen, but also to its partial pressure (oxygen tension).