What are Mitochondria?

Mitochondria are organelles found in the cytoplasm of most cells. They are essential to healthy living as they play an important role in the way cells function in the body. Mitochondria generate energy for cells to carry out activities. This energy is in the form of adenosine triphosphate (ATP). They also take part in cell signalling and help cells sense and adapt to their environment.

The amount of mitochondria found in cells depends on the particular types of cells. E.g., Liver cells can have as much as 2000. The amount can depend on the levels of energy required by the cell.

What are Mitochondria?
Section of mitochondria. Image Copyright: NoPainNoGain / Shutterstock

What is the Structure of a Mitochondrion?

A mitochondrion is an organelle about 0.75 – 3µm in diameter. Its structure, which tends to be bean-shaped, includes several compartments that carry out different important roles. However, mitochondria are not easily visible structures unless using staining of cells.

An outer mitochondrial membrane about 60 – 70Å thick containing proteins called porins surrounds a folded inner mitochondrial membrane. The outer membrane incorporates enzymes that contribute to the oxidation of adrenalin, the reduction of amino acids and the lengthening of fatty acids.

Just in between the inner and outer membranes of the mitochondrion is the intermembrane space. The inner membrane has proteins involved in several functions including redox reactions of oxidative phosphorylation, generating ATP in the matrix, regulating metabolites, importing substances as well as fusion and fission.

The inner membrane also has folds called cristae which provide a large area for the mitochondrion to carry out its reactions. This is where the energy production happens. In particular, it helps with aerobic cellular respiration.

The inner membrane surrounds a space called the matrix which has lots of enzymes, RNA, ribosomes, and mitochondrial DNA genomes.

The mitochondria-associated endoplasmic reticulum membrane (MAM) in a mitochondrion takes part in regulating the environment of the cell such as its acidity, alkalinity, and temperature.

The Role of Mitochondria in the Functions of a Cell

Mitochondria produce energy for cells through respiration. They produce ATP through a process called the citric acid cycle by oxidation of substances formed in the cytosol of the cell. A chemical called NADH is produced which is worked on by enzymes in the inner membrane, producing electrons which move around the internal system of the mitochondrion.

Mitochondria also helps maintain the environment of the cell (homeostasis) to keep the best conditions for optimum function. This is achieved by the storage and release of free calcium. Both cellular proliferation and cell division are regulated by mitochondria. Mitochondria themselves, however, actually divide by the process of binary fission.

Mitochondria also have a role in controlled cell death (apoptosis). They generate reactions which contribute to cell changes and eventually cell death. Up to 70 billion cells die in the average adult human every day. For children this is around 20 to 30 billion cells.

The Role of Mitochondria in Triggering Diseases

Mitochondria have such an important job to do in helping cells function properly that when they malfunction, they can cause diseases. Some malfunctions are believed to be due to mutations of mitochondrial DNA in about 15% of cases. Other times, mutations in genes will cause problems and lead to inherited diseases. It has been found that malfunctioning mitochondria play a role in conditions such as autism, heart failure, and cardiac dysfunction. People with Parkinson’s disease have a high level of mitochondrial mutations.

The typical symptoms of many mitochondrial diseases are loss of muscle coordination muscle weakness sight problems, liver disease, kidney disease, neurological conditions, and gastrointestinal problems to name just a few.


Further Reading

Last Updated: Jul 19, 2023

Deborah Fields

Written by

Deborah Fields

Deborah holds a B.Sc. degree in Chemistry from the University of Birmingham and a Postgraduate Diploma in Journalism qualification from Cardiff University. She enjoys writing about the latest innovations. Previously she has worked as an editor of scientific patent information, an education journalist and in communications for innovative healthcare, pharmaceutical and technology organisations. She also loves books and has run a book group for several years. Her enjoyment of fiction extends to writing her own stories for pleasure.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Fields, Deborah. (2023, July 19). What are Mitochondria?. News-Medical. Retrieved on June 17, 2024 from https://www.news-medical.net/life-sciences/What-are-Mitochondria.aspx.

  • MLA

    Fields, Deborah. "What are Mitochondria?". News-Medical. 17 June 2024. <https://www.news-medical.net/life-sciences/What-are-Mitochondria.aspx>.

  • Chicago

    Fields, Deborah. "What are Mitochondria?". News-Medical. https://www.news-medical.net/life-sciences/What-are-Mitochondria.aspx. (accessed June 17, 2024).

  • Harvard

    Fields, Deborah. 2023. What are Mitochondria?. News-Medical, viewed 17 June 2024, https://www.news-medical.net/life-sciences/What-are-Mitochondria.aspx.


  1. Teresa D. Teresa D. Serbia says:

    Is mitochondrial donation worth trying it? Will it help me to conceive?

    • Lon Dra Lon Dra Serbia says:

      My sister-in-law did it in Ukraine and you know it helped her to avoid a miscarriage. But every case is unique..

    • Rebecca Johnson Rebecca Johnson Serbia says:

      In simple words, mitochondrion is the cell’s energy station. Essentially, its work consists in supplying the cell with vital energy for its normal functioning. Women that went through multiple unsuccessful IVF attempts, as well as of older reproductive age, need to restore oocyte mitochondria. To carry out such a procedure, an egg donor with a high functional activity of mitochondria, a patient, and sperm for in vitro fertilization are required. Healthy functionally active mitochondria are taken from a donor’s oocyte and integrated with the patient’s cells. Next, fertilization with sperm and transfer of a healthy embryo into the patient’s uterus. Though the option is possible only when the eggs aren't damaged genetically. Mitochondrial donation makes it possible for a woman to carry and give birth to a child genetically related to both parents on her own. These programmes allow thousands of infertile women to carry and give birth to 'genetically related to them' babies. The package costs depend on the number of attempts. The prices for mitochondrial donation in Eastern Europe start with 6500 EUR - 1 shot. 9900 EUR - 2 shots. 14900 EUR - 5 shots. I believe every other method should be tried before moving onto more invasive treatment procedures. Hope this is useful.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.