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.

File:52-Exploring the Mechanism of Peroxodisulfate Activation with Silver Metavanadate to Generate Abundant Reactive Oxygen Species.jpg

52-Exploring the Mechanism of Peroxodisulfate Activation with Silver Metavanadate to Generate Abundant Reactive Oxygen Species

Introduction

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.

Types of ROS

• 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.

Sources of ROS

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.

Roles in Cellular Processes

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.

ROS and Disease

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.

Antioxidant Defenses

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.

See Also

• Oxidative Stress
• Antioxidants
• Free radicals
• Cellular Respiration

References

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