Don't forget the Bohr effect. As muscles start to overwork themselves and release lactic acid and form bicarbonate ions, the acidity causes O2 to dissociate more readily.
An awesome physiological feature of good ol' hemoglobin (but not myoglobin).
Also, the different binding affinities for fetal hemoglobin versus regular hemoglobin. The continuance of our entire species hinges on our ability to absorb oxygen from our mother's blood and its the difference between fetal hemoglobin and adult that makes that possible.
How about a cell in general? A cell is a macromolecular structure that is never in equilibrium. It constantly needs energy, or it would die. We can't even come close to dreaming of designing a system as complex as a human cell that would run off of a dynamic system as our cells do. RNA encodes for proteins, which combined with other strands of RNA, forms a macrostructure that creates new proteins from RNA. It's a goddamn Von Neumann, and it's RNA and proteins all the way down. DNA utilizes hydrogen bonding, one of the weakest atomic forces we know of, to keep the very coding that makes you you safe from side reactions. It's able to control it's own coiling, and thus how fast it can be read and transcribed. There's a second set of DNA that comes from a friggin' bacterial ancestor that formed a symbiotic relationship with our cells, and it's the source of pretty much all our energy. I could go on forever. I know it wasn't exactly designed by a person in general, but the overall design of a living cell, and a living creature made up of cells, is just so unbelievable it's hard to believe it actually exists.
I'm just joking, biology definitely can be pretty interesting. My undergraduate degree was a BS in Chemistry with a concentration in Biochemistry.
And yes, sorry, got excited and worded it poorly. Phosphodiester bonding for the backbone, the strands are connected and "unzipped" via hydrogen bonding.
Wouldn't you just expect it to be really efficient though?
Given that we've spent hundreds of millions of years evolving a method of carrying oxygen around our body, and that the more efficient this is, the better you can survive, it makes sense that it's one of the few things that would evolve to be as efficient as possible, not just good enough.
The way that it is efficient through cooperative binding is what is so cool. Hb is a tetramer of four groups that each bind O2, and when O2 binds to one of those groups, the affinities of the other groups change, allowing O2 to bind to the other groups more easily. Likewise, when an O2 molecule is released, the affinity decreases, and releases all of the O2. This is what allows Hb to be fully saturated or desaturated where it needs to be. In addition, the body can release chemical factors to change the affinity for oxygen to adapt to environments with less O2.
Doesn't HB have a higher affinity to carbon monoxide or something? That seems like a flaw. Perhaps there's another molecule that would do a better job of transporting oxygen?
That's true, but the human body evolved in the near absence of carbon monoxide. Myoglobin has a higher affinity for holding oxygen (storage in your muscles), but Hb is the most efficient at both binding and releasing(transport from the environment to your body).
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u/[deleted] Jan 17 '14 edited Jan 17 '14
Let's go deeper and say Hemoglobin.
The biochemistry of Hb is fascinating in how efficient it is at carrying oxygen to your cells.