Reactive oxygen species
Reactive oxygen species (ROS) are chemically reactive chemical species containing oxygen. They are crucial in cell signaling and homeostasis, but when produced in excess, they can cause significant damage to cell structures—a phenomenon known as oxidative stress.
Introduction[edit | edit source]
Reactive oxygen species (ROS) are molecules or ions formed by the incomplete one-electron reduction of oxygen. They are highly reactive due to the presence of unpaired valence shell electrons. While ROS play an essential role in cell signaling and metabolic processes, excessive ROS can lead to cellular damage.[1]
Types of ROS[edit | edit source]
- ROS include both free radicals and non-radicals. Major types of ROS include:
- Superoxide (O2•-): A free radical produced primarily within mitochondria. It serves as a precursor to most other ROS.
- Hydrogen Peroxide (H2O2): A non-radical ROS that can freely cross cell membranes. It can be converted into more reactive species, such as hydroxyl radicals.
- Hydroxyl Radical (•OH): The most reactive of the ROS. It is primarily produced from hydrogen peroxide via the Fenton reaction.[2]
Sources of ROS[edit | edit source]
ROS are produced by several processes within cells, including the mitochondrial electron transport chain, NADPH oxidases, and the metabolism of arachidonic acid. Environmental factors, such as ionizing radiation, pollutants, and certain drugs, can also induce ROS production.[3]
Roles in Cellular Processes[edit | edit source]
At low to moderate levels, ROS participate in several cellular signaling pathways and contribute to the host defense against microbial infections. They are also involved in the regulation of gene expression, cell proliferation, and apoptosis.[4]
ROS and Disease[edit | edit source]
Excessive ROS, leading to oxidative stress, can damage DNA, proteins, and lipids, which may contribute to aging and various diseases, including cancer, neurodegenerative disorders, cardiovascular diseases, diabetes, and inflammatory diseases.[5]
Antioxidant Defenses[edit | edit source]
Organisms have evolved antioxidant defenses to counteract the harmful effects of ROS. These include enzymatic antioxidants, such as superoxide dismutase, catalase, and glutathione peroxidase, and non-enzymatic antioxidants, such as vitamins C and E, glutathione, and various phytochemicals.[6]
See Also[edit | edit source]
References[edit | edit source]
- ↑ Sies, H.. (2015). Oxidative stress: a concept in redox biology and medicine. Redox Biology, 4, 180-183.
- ↑ Halliwell, B., & Gutteridge, J. M. (2015). Free radicals in biology and medicine. Oxford University Press.
- ↑ Droge, W.. (2002). Free radicals in the physiological control of cell function. Physiological reviews, 82(1), 47-95.
- ↑ Schieber, M., & Chandel, N. S. (2014). ROS function in redox signaling and oxidative stress. Current biology, 24(10), R453-R462.
- ↑ Finkel, T., & Holbrook, N. J. (2000). Oxidants, oxidative stress and the biology of ageing. Nature, 408(6809), 239-247.
- ↑ Powers, S. K., & Jackson, M. J. (2008). Exercise-induced oxidative stress: cellular mechanisms and impact on muscle force production. Physiological reviews, 88(4), 1243-1276.
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