Oxygen in biologic systems

Cadenas, F. and Sies, H. (1984). Low-level chemiluminescence as an indicator of singlet molecular oxygen in biological systems. Methods in Enzymology 105 221 231. 

A further role has been attributed to (Cu,Zn)-SOD the quenching of singlet oxygen. This raises, moreover, the question of the unlikely production of singlet oxygen in biological systems by non-photochemical means. 

This final reaction accounts for most of the known oxygen consumption by aerobic organisms. The cascade of redox reactions that couples the oxidation of organic substrates to reduction of molecular oxygen in biological systems is called electron transport, and is often presented schematically as shown in Figure 14-1. When substrates are oxidized by such a system, the rate and extent of substrate oxidation is directly dependent on, and can be measured by, the decrease in concentration of molecular oxygen, as will be done in this experiment. 

The third case (33) is particularly significant as far as biological oxidation is concerned. The metal, in fact, acts as an electronic relay between the ligand and oxygen. In biological systems, the two electrons come from NAOH. 

Barnett, J. E. G. Fluorine as a Substituent for Oxygen in Biological Systems Examples in Mammalian Membrane Transport and Glycosidase Action. Amsterdam Ciba Foundation Symposium Associated Scientific Publishers, 1972, pp. 95-115. 

N.I. Krinsky (1983). Singlet oxygen in biological systems. Trends Biochem. Sci., 2, 35-38. 

Taha, Z., R Kiechle, and T. Malinski (1992). Oxidation of nitric-oxide by oxygen in biological systems monitored by porph5rinic sensor. Biochem. Biophys. Res. Commun. 188(2), 734-739. 

L. 5erak, Measurement of oxygen in biological systems, "Electro-... 

As noted, oxonium salts are commonly used in the laboratory to effect the addition of an alkyl group onto oxygen. In biological systems, methylation can be effected using an onium salt, and it has been shown for many cases that the methylating species is a sulfonium salt, S-adenosylmethionine (SAM). 

Oxygenation Reactions and Singlet Oxygen 4.3.1 Photosensitized Oxygenations in Biologic Systems... 

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