6 Functions of Mitochondria

By  //  June 29, 2022

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Mitochondria are found in almost all eukaryotic cells and are known as the cell’s powerhouse. They get the name from the cellular activities that release energy. Mitochondria release energy and supply energy for various processes. Some cells in the human body do not have any mitochondria, while others have multiple mitochondria.

Oxymonad Monocercomonoides species are the only eukaryotes to lack mitochondria completely. Here’s more information about mitochondria including their functions.

What are Mitochondria?

Mitochondria (singular: mitochondrion) are membrane-bound organelles in almost all eukaryotic cells. They are typically oval or round in shape and 0.5 to 10μm in size. They are microscopic organisms and can be seen only by staining. When you see mitochondria under a microscope, you will observe two distinct membranes.  

The outer membrane transports proteins and contains enzymes for various functions. It has porins that help transport proteins. An intermediate space is present between the outer and inner membrane. The inner membrane also contains proteins. However, porins are absent in the inner membrane. The inner membrane allows permeability to a large variety of molecules.

It is the main site of ATP production. The inner membrane contains folds called cristae. These folds provide a higher surface area for chemical reactions synthesizing ATP. The internal space of the mitochondria is known as the matrix. Mitochondrial DNA is also present in the matrix along with enzymes for ATP production.

Functions of Mitochondria

ATP Production

Energy production in the form of ATP is the most fundamental function of Mitochondria. It uses food to produce ATP for cellular use. ATPs (Adenosine Triphosphate) is the body’s energy units that facilitate different bodily processes. Mitochondria produce ATP through the Krebs cycle or citric acid cycle. Krebs cycle produces NADH that is converted into ATP by enzymes. These enzymes are present in the cristae where ATP production takes place. Various processes within the body utilize the ATPs, including muscle contraction, phosphorylation, ion transport, etc.

Calcium Storage

Another essential function of mitochondria is the storage of calcium. Calcium is involved in several cellular processes like fertilization, muscle function, and blood clotting, besides hormone signaling and steroid synthesis. The release of calcium back into the cell contributes to releasing neurotransmitters to initiate a response. Mitochondria store the calcium to use it when needed. 

Heat Production

Besides ATP, mitochondria also play a major role in keeping the body warm. Factual based information shows that mitochondria use brown fat to generate heat through the proton leak process. It is known as non-shivering thermogenesis. Heat production through this process reduces over time as brown fat reduces as we age. 

Apoptosis

Apoptosis is a vital body process that helps kill unneeded cells in the body. It is critical to destroy and eliminate broken or degraded cells, or they may cause problems. Mitochondria decide the cells to be destroyed. They release the cytochrome C enzyme, which helps in destroying the cells.

Regulating Innate Immunity

Innate immunity refers to the defense mechanism of an organism present since birth. It recognizes and initiates action to kill antigens like allergens, viruses, and bacteria. Mitochondrial antiviral signaling proteins (MAVS) play a critical role in fighting viral infections. They provide a non-specific defense. An unregulated amount of MAVS in the cells can affect the functioning of the immune system.

Stem Cell Regulation

Mitochondria are believed to be highly important in regulating differentiation and reprogramming induced stem cells. Mitochondria have ROS (reactive oxygen species), which helps regulate somatic stem cell fate. Further studies about the role of mitochondria in stem cell regulation can prove immensely beneficial for the treatment of various diseases.

The Bottom Line

Mitochondria serve as the energy store or powerhouse in eukaryotic cells. They are microscopic, double-membrane, oval-shaped organelles. You can only observe them under a microscope after staining. They have two membranes, and the inner membrane has folds called cristae. These folds act as the main site of ATP production. Other functions of mitochondria include calcium storage, apoptosis, heat production, regulating innate immunity, and stem cell regulation.