Mitochondria Definition | Its Structure and Characteristics

Mitochondria definition: Mitochondria are sac-like cell organelles present in the cytoplasm of a cell, and they are engaged in energy production.

They do so by breaking down carbohydrates in the presence of oxygen.

In short, they are termed as powerhouses of the cell.

Also, they are called the energy currencies of the cell.

They are the power generators of all big and small living beings.

Unlike other cell organelles, they are extensively studied.

Their study is regarding body energy production and its implications in some complex diseases and disorders. Hence, mitochondria tests are done to check their function and efficiency.

Characteristics of mitochondria

Mitochondria are organs of special importance. These organelles are absolute requirements to sustain the physiological activities of the cells.

1. They are sac-like or pouch-like structures.

2. They are double membrane in nature.

The outer membrane is oval-shaped without folding.

While the inner membrane is folded to form partitions termed cristae.

In the gap of these folding lies the matrix, which encompasses all the enzymes and other substances that can help in the production of energy as ATP.

For more on mitochondria anatomy, refer to the page.

3. They are present in almost all the cells of the body except in Red Blood Cells.

4. They are freely floating in the cytoplasm and stay in the regions of high energy requirement.

5. Mitochondria are self-replicable, i.e., they can multiply on their own without the requirement of cells to divide. This characteristic feature helps replace old, worn out, and damaged mitochondria with new and healthy mitochondria. This process happens many times in the life cycle of a cell.

6. Mitochondria have their own genetic material as single-stranded DNA. This DNA is unlike the double-stranded one in the cell nucleus.

7. They have the capacity to generate mRNA, which helps in the formation of proteinaceous enzymes required for the respiratory chain.

8. The mitochondria have many enzyme complexes which, in series, help in the formation of energy, i.e., adenosine triphosphate (ATP).

9. In times of stress or injury, mitochondria can also play a role in cell death. This cell death meditated by mitochondrial damage is in the form of apoptotic cell death. The mitochondrial damage leads to the release of cell death factor (caspases).

10. If the mitochondria are killed, the whole cell dies immediately. That is the reason why, when cyanide is consumed, the person dies immediately. Cyanide immediately arrests the energy-forming complexes, leading to energy failure and death.

Brain mitochondria

The mitochondria are transported or migrated through the long nerve cell. The Brain is a high energy-demanding organ, and hence, the number of mitochondria is higher in nerve cells. Nerve cells have a central nerve body and an extended lengthy axon with a nerve tip at the end. The mitochondria are formed in the nerve body and then migrate towards the nerve tip. The nerve tip is involved in signal transmission, nerve growth, and branching (plasticity). Hence, healthy mitochondria are concentrated at the tip of nerve endings to cope with the high energy demand, and those mitochondria that are worn out, aged, and damaged are migrated back from the nerve tip to the nerve body for digestion.