Oxygen metabolism and human disease

See also Antioxidants, Reactive Oxygen, Oxygen Metabolism and Human Disease, P-Carotene, G Proteins in Vision, Lipid-Soluble Vitamins, Vitamins... 

See also Pyrimidine Dimers, Thymine Dimers Photoreactivation, Postreplication Repair, RecA / SOS Response, Antioxidants (from Chapter 15), Oxygen Metabolism and Human Disease... 

See also Oxygen Metabolism and Human Disease, Antioxidants... 

In many crucial biological processes, such as oxygen transport, electron transport, intermediary metabolism, metals play an important part. Therefore, disorders of metal homeostasis, metal bioavailability or toxicity caused by metal excess, are responsible for a large number of human diseases. We have already mentioned disorders of iron metabolism (see Chapter 7) and of copper metabolism (see Chapter 14). The important role, particularly of redox metals such as copper and iron, and also of zinc, in neurodegenerative diseases, such as Parkinson s disease, Alzheimer s disease, etc. has also been discussed (see Chapter 18). We will not further discuss them here. 

The accompanying table lists the essential elements in the human body. Of special interest are the trace elements, such as iron (Fe), copper (Cu), zinc (Zn), iodine (I), and cobalt (Co), which together make up about one percent of the body s mass. These elements are necessary for biological functions such as growth, transport of oxygen for metabolism, and defense against disease. There is a delicate balance in the amounts of these elements in our bodies. Too much or too little over an extended period of time can lead to serious illness, retardation, or even death. 

Oxygen is a dangerous friend. Overwhelming evidence indicates that oxidative stress can lead to cell and tissue injury. However, the same free radicals that are generated during oxidative stress are produced during normal metabolism and thus are involved in both human health and disease. 

There is a considerable body of research that indicates that vitamin E has important antioxidant, or redox-modulatory, functions in cell membranes and other lipidic sites in the body, which include especially the prevention of pro-oxidant (including oxygen free radical) damage by peroxidation of the polyunsaturated lipids. Recent studies suggest that vitamin E also has cell-signaling functions. The different chemical forms of vitamin E have different metabolic fates, and may also have different functions from each other. However, the roles and significance of vitamin E in chronic human diseases have yet to be fully elucidated. 

As noted in a very informative summary by McKersie, although molecular oxygen is required by humans and other oxic organisms for energy metabolism and respiration, it plays an important role in a number of significant diseases and degenerative conditions. Such adverse health conditions are... 

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