Mitochondria: you’ve got a friend in me

When we think about our friends, we think about the people who support us, those that would do anything for us. But have you ever considered that you may in fact have a friend inside your body, an organelle that works tirelessly day and night to ensure that you survive? Let me introduce you to the mitochondrion, the friend you never knew you had.

Mitochondria are remarkable organelles that are present in almost every cell in eukaryotes, like us humans. With its distinct structure including an outer membrane, an inner membrane that is folded and layered to form structures called cristae and a viscous space called the matrix, mitochondria are able to have a central role in carrying out various important functions.

Mitochondria are the powerhouses of the cell

Throughout school you may have heard the phrase that ‘mitochondria are the powerhouses of the cell’ far too often. What exactly does this phrase mean and most importantly why does this matter? Well, the mitochondria are crucial for energy transfer, transferring energy from proteins, fats and carbohydrates in the food we eat to an energy store called adenosine triphosphate (ATP) that our cells, organs and tissues can utilise. In fact, even as you are sitting reading this article your mitochondria are continuously working hard to transfer sufficient energy, by the process of aerobic respiration, so that your tissues and organs can function. You can picture mitochondria working away transferring energy, a bit like a power station or powerhouse transferring energy to our homes. Some organs have a particularly high energy transfer demand to support processes, such as active transport or cell division. There are therefore high concentrations of mitochondria and high rates of aerobic respiration in organs such as the brain, heart, liver and kidneys.

Mitochondria – the jack of all trades

The role of the mitochondria extends far beyond aerobic respiration transferring energy for your cells. Mitochondria are vital for many other roles in your body including signalling, the immune response, cell death and regulating calcium levels. Mitochondria have been found to serve as a platform to initiate signals between cells where protein to protein interactions can occur. Studies have also shown that mitochondria ‘upregulate.’ This means they increase the production, of ATP in response to cell synthesis stimuli.

These communication signals govern proper functioning and development of our bodies. Interestingly, mitochondria have shown to have a critical role in the immune response as it can regulate factors such as the activation, differentiation and even death of specific immune cells when necessary.

^ A diagram of mitochondria

Additionally, the process of cell death known as apoptosis, which ensures our proper development such as ensuring that we have five distinct fingers, is also highly regulated by mitochondrial signals. The storage and transport of calcium is a further role that the mitochondria are highly involved in, this process is essential for extremely rapid biological processes like muscle contraction as well as long term biological processes like organ development. On top of everything, new research is constantly emerging demonstrating additional roles that mitochondria are involved in. Impressive, isn’t it? The mitochondria really are the jack of all trades.

You’ve got troubles, I’ve got ‘em too

Sometimes however, there can be faulty mitochondria present in individuals due to mistakes in either nuclear DNA or mitochondrial DNA. Nuclear DNA which is found in the nucleus and is responsible for our physical attributes is different from mitochondrial DNA which is located in the mitochondria and largely contributes to the energy transfer process. However, both DNA types contain instructions for generating proteins that are involved in maintaining proper mitochondrial function and faults in either can lead to mitochondrial dysfunction. Detrimental effects can occur at certain thresholds of faulty mitochondria, as cells begin to fail and die without sufficient energy. This can be particularly damaging for organs and tissues such as the brain, muscle, heart and kidneys that need substantial energy transfers to function.

Since mitochondria play a role in many different functions, there are hundreds of mitochondrial diseases that exist. These can present with varying symptoms including: heart problems, muscle weakness, fatigue, liver disease, hearing disorders and sometimes the disease can even be fatal. However, as mitochondrial DNA is solely inherited from mothers, a fairly new technique called mitochondrial transfer has meant that biological inheritance for some cases of mitochondrial disease can be blocked. This technique has sometimes been referred to as ‘3 parent babies’ since the approach removes nuclear DNA from the affected mother’s egg cell containing faulty mitochondria and transfers it into a woman donor’s egg cell, which has had its nuclear DNA removed but still contains healthy mitochondria. Therefore, the resulting baby will still have nuclear DNA from its father and mother but also have mitochondrial DNA from a woman’s donor egg.

Hope in the form of research

Despite the serious problems that can be caused by the presence of faulty mitochondria, advances in research mean that there is exciting promise in the field of mitochondrial research. Everyday many researchers around the world are exploring novel ways to treat and understand the mechanisms behind mitochondrial disease and there is hope that one day we will be able to treat and prevent disease related to this organelle that we simply could not live without. With that all being said, I hope you will be able to appreciate that you really do have a friend in mitochondria.

Find out more from Anitta’s video about Mitochondria