Mitochondria is one of the vital cell organelles present inside the cell.
Every cell has at least one or more numbers depending on the requirement.
The cells of those organs with high physiological activity posses a higher number of mitochondria.
Similarly, those organelles with low physiological activity have less number of mitochondria.
Further, in a typical cell, their location varies within the cytoplasm. But in general they are more concentrated in the regions of the cell with high physiological activity.
Structure and Function of Mitochondria
Mitochondria structure is quite compact, and all of its functions happen within this structure.
Structure of mitochondria
They are sac-like double membranes structures present in the cytoplasm of the cell.
They can be seen only under an electron microscope.
Their shape differs from being either spherical, club, oval or even thread like structures.
They are divided into two compartments, i.e. an inner compartment and an outer compartment.
The inner compartment lies within the inner membrane. The outer compartment is in between outer membrane and inner membrane.
The inner compartment is also called as matrix and is surrounded by an inner mitochondrial membrane. This membrane is divided into several folds within which lies the matrix. The membrane also has permeability, and hence the substances can move from matrix to fluid in the outer compartment and vice-versa.
The folding on the inner membrane is termed as cristae which have elementary particles and some enzymes.
The enzymes on cristae and those in the matrix are involved in the production of energy through the breakdown of carbohydrates.
Even fats and proteins converted to some form of carbohydrates mitochondria. Even the single-stranded DNA lies in the matrix.
The outer compartment is surrounded by outer mitochondrial membrane towards exterior and also by inner mitochondrial membrane towards interiors of mitochondria.
This outer mitochondrial membrane is smooth without any folding or projections. It is selectively permeable to substances. That is from the cytoplasm into the mitochondria and also from mitochondria into the cytoplasm.
Thus it can act as a reserve for various substances needed for mitochondrial energy generation and excretion of related waste bi-products.
Check out →Mitochondrial characteristics
1. It is a well-known fact that mitochondria are responsible for cell energy supply. Cell requires energy for many purposes like DNA, RNA, protein synthesis, cell division etc. Most of the processes occur due to bond formations or with the involvement of enzymes and phosphate. These enzymes and phosphorylations are energy dependent. The required energy is supplied by mitochondria to the cell.
2. Mitochondria produce energy in the form of ATP (adenosine triphosphate) by the breakdown of carbohydrate substrates in the presence of oxygen. This is how the food in the body is converted to energy. Once we consume food, it is digested and absorbed into the blood as glucose. This is supplied to each and every cell and organ in the body. The glucose is then broken down to release the energy.
Check out→How food is converted to energy in the body for more details.
3. These are the cell organelles where the TCA cycle (tricarboxylic acid cycle) and other respiratory cycles of the cell take place.
4. Many bi-products like glutarate, glyco-oxalic acid are produced during the TCA cycle. These biproducts are further utilized by the cell to form glutamine, glycine like amino acids which are essential for normal physiology and metabolism of the cell.
5. Mitochondria is involved in calcium homeostasis in the cell. Calcium is taken into the cell from outside through the cell membrane. This calcium is stored in calcium vesicles inside the cell. But when required, calcium is released and again stored in the vesicles. However, mitochondria also take up calcium and also release it back into cytoplasm. Read for more on mitochondria and calcium
6. They promote cell growth and also signal transmission. In especially nerve cells they are concentrated at the nerve ending to support nerve growth and also supply energy for nerve conduction.
7. Mitochondria are also partly responsible for cell death in case of trauma. The membrane of mitochondria releases apoptosis factors leading to programmed cell death. Even, disruption of mitochondria will lead to sudden stoppage of energy supply leading to shock and immediate death.
8. They also generate oxidative radicals during energy formation. These oxidative radicals are necessary for various other reactions. But the main contribution of these oxidative radicals is in ageing.
9. Mitochondria support nerve conduction by helping neurotransmitter release. Hence, there are more number of mitochondria near the nerve endings, especially at the synapse. These mitochondria produce sufficient energy for the release of neurotransmitters at the nerve junctions.
10. Abnormalities in mitochondria can lead to many diseases like neurodegeneration, cardiac problems, cancer etc.