Conflict? I'd say inaccuracy. Let's remind ourselves of what you said that pushed me into action:
Alrighty then.
To make this even simpler, I'll just stick to the example that One Brow mentioned(and you ignored):
I'll try to be simple and succinct:
the body has two proteins that it uses to shuttle oxygen around the body: hemoglobin, and myoglobin. Myoglobin and hemoglobin are extremely genetically related-- the major difference is this: hemoglobin is assembled from several similar subunits (let's call them 'globin-monomers' for the sake of this conversation) that came to fruition from gene duplication. Well, the question becomes this: what was the original function of the gene that coded for the 'globin-monomer' before it duplicated?
Answer: it was myoglobin (or it's analogue at that point in time).
Myoglobin is coded by the gene called MB
here is the link for the gene info
If you want to think of it this way, 4 myoglobins that assemble together make a structure really, really similar to hemoglobin. This is how hemoglobin arose. This has been proven ad-nauseum.
Now, as anyone with some basic human physiology might know, hemoglobin and myoglobin serve completely different functions: and it's purely because of how many subunits the protein has.
Let's look at their oxygen-binding curves, to try and point out what I am talking about:
Since hemoglobin has 4 major subunits, in other words 4 spots where oxygen can bind, it has a sigmoidal curve. What this means is that it doesn't bind oxygen extremely tightly right away-- the binding is a lot more loose, and the affinity of hemoglobin to oxygen is very modifiable by factors that exist in the bloodstream (1,3 BPG, H+, etc.)
Depending on what the summated state of the subunits of hemoglobin are, it has different states that either bind oxygen tightly or release it. These two states make it possible for hemoglobin to bind oxygen tightly when it comes in through the lungs and then release it easily when it gets to the body tissues (that need the oxygen).
In contrast, myoglobin is usually more involved in the body tissues where the oxygen is used. It binds oxygen with a greater affinity than hemoglobin.
This is not by accident. It receives the oxygen transported by hemoglobin and keeps it there until it is needed by the body tissue.
Hence, hemoglobin, stemming from the historic-myoglobin, now serves a different function because it's duplicated subunits make it's affinity more sensitive to oxygen levels, allowing it to take in loads of oxygen from the lungs, and give up loads of oxygen to the myglobin in the tissues, where it can then divvy up the oxygen to the tissues that need it most.
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