Mitochondria: Structure, Function and Role in the Cell

The article is written by Pavlo Chaika, the chief editor of the "Piznavayka" magazine. Since its founding in 2013, Pavlo Chaika has been dedicated to popularizing science in the world. The main goal, both of the magazine and of this article, is to explain complex scientific topics in a simple and accessible language.



  • Definition

  • Quantity in a Cell

  • Size

  • Location

  • Origin

  • Structure

  • Functions

  • References and Further Reading

    Discovery of mitochondria happened back in the 19th century. They attracted the attention of biologists by their elongated zigzag-like form. What do mitochondria mean in science? The term “mitochondria” is composed of two Greek words: “mitos” – string and “chondros” – grain. In our article, we’ll talk about why the mitochondria are so important, and what is the role of mitochondria in the cell


    Mitochondria are a two-membrane organelle of a eukaryotic cell. What do mitochondria do? The main task of mitochondria is the oxidation of organic compounds, the synthesis of ATP molecules, with the next use of the energy formed after their disintegration. Mitochondria are the energy base of cells; they are a kind of stations that produce the energy necessary for cells.

    Quantity in a Cell

    The number of mitochondria in cells can vary from a few pieces to thousands of units. Cells, which are making the synthesis of ATP molecules, have a greater number of mitochondria.


    Mitochondria have different shapes and sizes, there are rounded, elongated, spiral and cupped representatives among them. How big are mitochondria? Usually, their shape is round and elongated, with a diameter from one micrometer to 10 micrometers long.


    Mitochondria picture.

    Mitochondria can move through the cell (they do this thanks to the cytoplasm) and remain motionless in place. They always move to places where energy production is needed the most.


    Mitochondria are located in the cytoplasm of cells along with other organelles of the cell.


    Scientists believe that mitochondria originated from aerobic bacteria introduced into another prokaryotic cell. These bacteria began to supply the cell with ATP molecules instead of receiving the nutrients they need. In the process of evolution, they lost their autonomy, transferring a part of their genetic information to the nucleus of the cell, becoming a cell organelle.


    Mitochondria consist of:

    • two membranes, one of them is internal, the other is external,
    • intermembrane space,
    • matrix – the inner contents of the mitochondria,
    • the cristae – this is the part of the membrane that has grown in the matrix,
    • protein of the synthesizing system: DNA, ribosomes, RNA,
    • other proteins and their complexes, including a large number of various enzymes,
    • other molecules

    You can see the mitochondrion structure on this picture.

    Structure of Mitochondria

    The outer and inner membranes of mitochondria have different functions, and for this reason, their structure differs. The outer membrane is similar in its structure to the plasma membrane, which surrounds the cell and plays a role of a protective barrier.

    Mitochondrial enzymes are located on the inner membrane of the mitochondria. They form multienzymatic systems.

    Mitochondria have their own protein synthesis system: DNA, RNA, and ribosomes. The genetic apparatus has the form of a ring molecule, a nucleotide, almost like bacteria. Some of the necessary proteins for mitochondria they synthesize by themselves and some obtained from the cytoplasm since these proteins are encoded by nuclear genes.


    What is the function of mitochondria? The main function of mitochondria is to supply the cell with energy. The energy is extracted from organic compounds through numerous enzymatic reactions. Some of these reactions occur with the participation of oxygen. And these reactions occur, both within the mitochondria itself and in its matrix.

    Yet, the most important purpose of mitochondria in the cell is to actively participate in “cellular respiration”, which includes many chemical reactions.

    References and Further Reading

    • Henze K, Martin W (November 2003). “Evolutionary biology: essence of mitochondria”. Nature. 426 (6963): 127–128. Bibcode:2003Natur.426..127H. doi:10.1038/426127a. PMID 14614484.
    • Karnkowska A, Vacek V, Zubáčová Z, Treitli SC, Petrželková R, Eme L, Novák L, Žárský V, Barlow LD, Herman EK, Soukal P, Hroudová M, Doležal P, Stairs CW, Roger AJ, Eliáš M, Dacks JB, Vlček Č, Hampl V (May 2016). “A Eukaryote without a Mitochondrial Organelle”. Current Biology. 26 (10): 1274–1284. doi:10.1016/j.cub.2016.03.053. PMID 27185558.
    • “mitochondria”. Online Etymology Dictionary.
    • Campbell NA, Williamson B, Heyden RJ (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 978-0-13-250882-7.
    • Siekevitz P (1957). “Powerhouse of the cell”. Scientific American. 197 (1): 131–140. Bibcode:1957SciAm.197a.131S.

    Author: Pavlo Chaika, Editor-in-Chief of the journal Poznavayka

    When writing this article, I tried to make it as interesting and useful as possible. I would be grateful for any feedback and constructive criticism in the form of comments to the article. You can also write your wish/question/suggestion to my mail or to Facebook.