Oxygen transport and hemoglobin

It may come as a surprise that CO is synthesized by the human body and has roles in human metabolism. Specifically, an enzyme that degrades heme, a constituent of hemoglobin, our oxygen-transporting protein, makes CO, which is a neurotransmitter. Much more about neurotransmitters follows in chapter 21 when we talk about the central nervous system. For the present, just understand that specialized cells known as neurons are the conduits for communication in the nervous system. Neurotransmitters are small molecules that relay information from one neuron to another. Neurotransmitter CO is made, functions, and is quickly destroyed. Personally, I find it surprising that CO has such a critical role in the nervous system. Surprised or not, there it is and there is no doubt about it. 

Kasper, S. Grune, F. Walter, M. Amr, N. Erasmi, H. Buzello, W. The effects of increased doses of bovine hemoglobin on hemodynamics and oxygen transport in patients undergoing preoperative hemodilution for elective abdominal aortic surgery. Anesth. Analg. 1998, 87, 284—291. 

The cationic charge in blood is neutralized by two major anions, Cl and HC03. The chloride ion plays a role in acid-base balance, maintenance of osmotic pressure within an acceptable range, and oxygen transport by hemoglobin. The bicarbonate anion is the form in which most waste CO2 is carried in the blood. 

Coordination compounds play important roles in nature. Chlorophyll, which is involved in photosynthesis in plants, is a coordination complex of magnesium. Hemoglobin, the oxygen transporter in the human body, is a coordination complex of iron. Vitamin B12, necessary for the prevention and cure of pernicious anemia, is a coordination complex of cobalt. In all three compounds, the metal ion is in an approximately octahedral environment, its coordination number is 6, and bonded to it are the four nitrogen atoms of a planar porphyrin-hke ring. The basic planar ring structure is closely related to that of the extremely stable blue pigment, Cu(II)phthalo-cyanine. 

Blood consists of90% water and 10% dissolved solids (proteins, salts, etc.). Blood proteins perform various functions. In one liter of blood, for example, there are 133 X 10 molecules of hemoglobin (for oxygen transport), 17.3 X 10 molecules of albumin (transport of other molecules), 1.63 X 10 molecules of 7-globulin (protective functions), plus hormones, etc. Oxygen transport is by far the most important function of the blood. 

Meldon, J.H., Smith, K.A. and C.K, Colton. "Analysis of 2,3-dlphosphoglycerate-mediated, hemoglobin-facilitated oxygen transport In terms of the Adair reaction mechanism." Advances In Experimental Medicine and Biology 37A (1973) 199-205. 

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