[Organism defense against reactive oxygen species].

Reactive oxygen species (ROS) are constantly formed as side products of biological reactions in which electron transfer goes on. ROS include superoxide anion radical O2*, hydroxide radical OH, hydrogensuperoxide radical HO2, hydrogen peroxide and singlet oxygen. The maintenance of homeostasis at the redox level is particularly important for many biological processes such as: DNA synthesis, enzymes activation and regulation genes, regulation of cellular cycle and programmed death of the cell. Cells protect themselves against oxidative stress by means of antioxidants enzymes and compounds which in their structure have redox sensitive spots.