Free Radical Reactions: Definition & Examples

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

In this lesson we will learn about free radicals. We will discover how they can cause damage to the body and how they can be helpful in other reactions.

Free Radicals

You might have heard that blueberries are important to eat because they are high in antioxidants. Why are antioxidants so important? One reason is that they stop free radical reactions from occurring in our body. These free radical reactions can cause a lot of damage, so it is important to stop them from occurring.

Free radicals are very reactive species ('species' here refers to a molecule or atom). Most reactions occur with a pair of electrons reacting. However, free radicals have a lone electron. Electrons are more stable as a pair (since that fills up their atomic orbitals). When a compound has a lone electron, it will quickly react with another compound, stealing an electron in order to fill up its orbital and become stable again. The problem with this is that since the free radical has only stolen a single electron, we are now left with another compound with a lone pair, making a new free radical. This continues until it either finds another free radical to react with, or it is quenched with something such as an antioxidant.

In this reaction the free radical on the oxygen reacts with itself; once two free radicals find each other they can resolve the free radical
Free Radical Reaction

Free Radicals in the Body

Free radicals are particularly dangerous in the body. The damage that they cause may lead to many diseases, including heart disease, Alzheimer's, and cancer. It is normal to have a few free radicals in the body; in fact, they are used in the process of breaking down food into energy and also help the body fight off diseases. But when there are too many free radicals they start to find other places to react, such as the cellular membrane. This breaks down the cellular membrane, leading to cell mutation and death.

Antioxidants can quell free radicals in a variety of ways. For example, the antioxidant may be a large, complex molecule that allows the free radical to simply move around on itself. In this way no one atom needs to hold the free radical; instead, the antioxidant is able to share it with several atoms. Since it is being shared with other atoms, the free radical is no longer as reactive. Antioxidants can also break down the molecule with the free radical into individual atoms and electrons so that it is no longer reactive.

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