Mitochondria

Mitochondria are tiny organelles in cells that are involved in the release of energy from food. This process is called cellular respiration, which is why mitochondria are often called power plants of the cell. Cells that require a lot of energy, such as muscle cells, can contain thousands of mitochondria. In addition to cellular respiration, mitochondria also play a key role in the ageing process as well as in the development of degenerative diseases

When the breakdown products of food digestion enter the cell, a series of chemical reactions take place in the cytoplasm. This allows some of the energy trapped in these products to be released and incorporated into the cells’ universal energy supplier called ATP (adenosine triphosphate). Remaining molecular fragments of this process enter the mitochondria and are finally converted into carbon dioxide and water in a complex series of steps. The energy trapped in these fragments is converted into further ATP. The ATP molecules produced in this way can then be used by the cell to provide the energy needed to function

During cellular respiration, highly reactive molecules called free radicals are formed in the mitochondria. Perhaps the best known free radical produced in this way is the superoxide radical O2-. Free radicals are potentially very damaging to cell components such as proteins and genetic material such as DNA and RNA. If too many free radicals are released in the mitochondria, the damage can be severe and ultimately lead to the death of the cell

To protect against free radical damage, mitochondria produce their own antioxidant enzymes. One of these enzymes is known as superoxide dismutase or SOD

Research has shown that substances found in some fruits and vegetables have an antioxidant effect. This means that they can neutralise free radicals in laboratory tests. It was thought that eating these foods or extracts made from them would help the body or mitochondria neutralise and remove harmful free radicals

However, recent research suggests that antioxidants work differently in the body than they do in the laboratory. Some antioxidants, particularly a class of plant chemicals known as polyphenols, are now thought to have a direct effect on mitochondria. It seems that they stimulate mitochondria to produce energy from food more efficiently, so that they produce fewer free radicals and neutralise them more quickly

Thus, when mitochondria are not functioning efficiently, their energy production capacity is also reduced. More free radicals escape as a result and damage the cell, which can lead to early cell death