Mitochondria, Structure, Functions, and Location

Cells require energy for survival and proper functioning. Mitochondria are membrane-bound cell organelles found in eukaryotic cells. They are commonly known as the cell’s powerhouse because they supply power (energy) to the cells. 

Mitochondria (singular mitochondrion) have their own DNA (deoxyribonucleic acid), and along with the role of energy generator, these also have many other roles like determining cell life, calcium storage, and heat production.  

Structure of Mitochondria

Mitochondria in animal cell
Structure of Mitochondria in Animal Cell

Mitochondria are rod or oval-shaped organelles. These are small cell organelles ranging from 0.75 to 3 µm (similar in size of bacterial cells) in size. Unlike other small cell organelles, double membrane encloses the mitochondria. The structural components of mitochondria are as follows:

  • Outer membrane: It is smooth and is made up of porins that forms a channel for the movement of proteins. It covers the entire mitochondria and consists of enzymes carrying many functions.
  • Inter membrane space: It separates the outer membrane and inner membrane.
  • Inner membrane: It is also made up of proteins. It is impermeable to many molecules as there is the absence of porins. However, special membrane transporters help in transferring some molecules. Maximum ATP (adenosine triphosphate) is produced in this layer.
  • Matrix: It is the space inside the inner membrane and the place where DNA lies. It also harbors enzymes that are required in ATP production.
  • Cristae: These are folds in the inner membrane of mitochondria that increase the mitochondria’s surface area. These help in increasing the rate of chemical reactions in the mitochondria.
  • DNA: Mitochondria has its own DNA similar to bacterial DNA. Mitochondrial DNA (mtDNA) consists of 17,000 base pairs and holds instructions for synthesizing several proteins. A child receives mtDNA from their mother.
Structure of mitochondrial DNA
Structure of human mitochondrial DNA

Function of Mitochondria

The functions of mitochondria are as follows:

  1. Energy Production: ATP is the energy currency of the cell. It is a complex chemical compound and is found in almost all organisms. Most of the ATP found in the body is formed here by a series of chemical reactions called Krebs cycle. Food consumed breakdowns into energy inside the mitochondria which is used by the cell. The chemical reaction involved in converting food to energy is called oxidative phosphorylation. Since cell processes that produce high amount of energy occur inside mitochondria, these are also called power house of the cell.
  2. Storage of Calcium: Calcium is an important component in the human body for various cellular processes like triggering neurotransmission, muscle movement, fertilization, blood clotting, etc. Mitochondria help in quick absorption of calcium and also store them until they are required.
  3. Heat Production: Mitochondria present in brown fat, by the process of protein leak, produce heat. The amount of brown fat is higher in babies because maintaining proper body temperature is crucial in babies.
  4. Signaling cell death : Cell death or apoptosis is the natural phenomenon of any cell. Mitochondria signal which cell is damaged or old and needs to be cleared away. These produce cytochrome C, a chief enzyme involved in the destruction of cells during apoptosis.

Location and Number of Mitochondria

Mitochondria are present in the cytoplasm of the eukaryotic cell. Their number vary in different cells based on the energy produced and required. For example, 40% of the cytoplasm of heart cells is occupied by mitochondria since these cells require maximum energy. Similarly, liver cells have the maximum number (2000 per cell), but the mature RBC lacks mitochondria. 

How to Boost Mitochondria?

It plays a crucial role in cell’s. Different human activities have different affect on their functions like exercise increases their number but consuming more calories can decrease their number and adversely affect the function of mitochondria. There are various things an individual can do to boost the functions of mitochondria which are as follows:

  • Counting calories: Consuming more calories leads to obesity and increases the chance of oxidative stress. The stress causes dysfunction in mitochondria. So, consuming few calories to maintain the proper functionality of mitochondria. 
  • Avoid refined carbohydrates: Refined carbs (carbohydrate) like soft drinks, pasta, cereals, etc., can lead to a significant change in the mitochondria of the brain, leading to type 2 diabetes and Alzheimer’s disease. So, avoiding such carbs is best for boosting the mitochondria. 
  • Exercise: Physical exercise for at least 30 minutes a day can boost the intake of oxygen, which is a vital component for the proper functioning of mitochondria.
  • Sleep: A person should at least sleep for 8 hours for healthy mitochondrial functions.
  • Indulge in relaxation activities: Relaxation activities like meditation, spa, sauna, etc., help reduce the stress of daily life, which is an important cause of degradation of mitochondria in cells. So, meditation, heat therapy (sauna), spa, and massage are very important for boosting mitochondrial activity. 
  • Consume 2-3 meals in a day: Consuming a balanced diet at an interval of 8-10 hours at least 2 times a day is another factor to boost mitochondrial activity.

Some Facts about Mitochondria

The must-know facts about mitochondria are as follows:

  • They can easily change their shape.
  • They grow bigger if cells require more energy and can die or become inactive when not in use.
  • Since mitochondria have their own DNA, which plays a role in synthesizing some proteins.
  • Although mitochondria is absent in bacteria, they possess many similarities to bacteria like the size is similar.
  • Mitochondria can also produce small amounts of carbon dioxide as a by-product during the citric cycle.
  • They produce highest number of ATP in the cell hence termed powerhouse of the cell.

References

  • Verma, P. S., & Agarwal, V. K. (2019). Mitochondria. In Cell Biology, genetics, Molecular Biology, evolution and ecology (13th ed., pp. 191–219). essay, S. Chand and Company Limited.
  • Mitochondria. Genome.gov. Retrieved 25 July 2022, from https://www.genome.gov/genetics-glossary/Mitochondria.

Ashma Shrestha

Hello, I am Ashma Shrestha. I am currently pursuing my Master's Degree in Microbiology. Passionate about writing and blogging. Key interest in virology and molecular biology

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