What Is A Free Radical - Ústav lékařské chemie a biochemie

Reactive oxygen species (ROS, ‘oxygen radicals’) can be
derived from intermediates of oxygen reduction to water:
O 2
+4 e-
(+4 H + )
+1 e-
O 2·–
superoxide
+2 e-
(+2 H + )
H 2 O 2
hydrogen peroxide
+3 e-
(+3 H + )
2H 2 O
OH·
hydroxyl
radical
( +H 2 O )
Superoxide
O 2·–
• Sources in the body:
– Escape of electrons to oxygen
- Respiratory chain in mitochondria
- Other similar redox carrier systems, e.g. microsomal
cytochrome P450 monooxygenase
– NAD(P)H Oxidase:
- Phagocytes (”respiratory burst”)
- Non-phagocytic cells
– Some enzymes:
- Xanthine oxidase
- Cyclooxygenase
- Lipoxygenase
– Reaction of FeII-hemoglobin with oxygen
– Autoxidation (reaction with oxygen) of various compounds
(ascorbate, glutathione and other thiols, catecholamines)
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