Mitochondria are a double-membrane-bound organelle found in most of the eukaryotic organisms. They are free floating organelles found within the cytoplasm which functions like a digestive system of the cell. They play a major role in breaking down the nutrients and generates energy-rich molecules for the cell. Many of the biochemical reactions involved in cellular respiration takes place within the mitochondria. The term ‘mitochondrion’ is derived from a Greek word which means a thread like granules and was first described by German pathologist -Richard Altmann in the year 1890.

Structure of Mitochondria

Mitochondria are a double membrane, rod shaped structure found in both plant and animal cells. The size of the mitochondria ranges from 0.5 to 1.0 micrometre in diameter. The structure of mitochondria comprises of an outer membrane, an inner membrane, and a gel-like material called the matrix. The outer membrane and an inner membrane are made of proteins and phospholipid layers and are separated by the intermembrane space.

The outer membrane, covers the surface of the mitochondrion and has a large number of special proteins known as the porins. It is freely permeable to ions, nutrient molecules, energy molecules like the ADP and ATP molecules.

The inner membrane of mitochondria is complex in structure, which is folded over many times to create a layered structures called cristae and helps in increasing the surface area inside the organelle. The cristae and the proteins of the inner membrane aids in the production of ATP molecules. The inner membrane is strictly permeable only to oxygen and to ATP molecules. A number of chemical reactions takes place within the inner membrane of mitochondria.

The matrix of the mitochondria is a viscous fluid which contains a mixture of enzymes and proteins. The mitochondrial matrix comprises of the ribosomes, soluble enzymes, inorganic ions, mitochondria’s DNA, nucleotide cofactors, and small organic molecules. The enzymes present in the matrix play an important role in the synthesis of ATP molecules.

The diagram below shows the structure of the mitochondria.


Function of Mitochondria

The mitochondria also affect human health, like mitochondrial disorder and cardiac dysfunction and they also play important role in the aging process.

Mitochondria are known as the powerhouses of the cell. It is involved in various cellular activities like cellular differentiation, cell-signalling, cell senescence, controlling of cell cycle and also in the cell growth.

The most important function of the mitochondria is to produce energy through the process of oxidative phosphorylation. It is also involved in the following process:

  1. Regulates the metabolic activity of the cell.
  2. Helps in detoxifying ammonia in the liver cells.
  3. Play an important role in the process of apoptosis or programmed cell death.
  4. Building certain parts of blood and hormones like testosterone and oestrogen.
  5. Maintains proper concentration of calcium ions within the compartments of the cell.

Stay tuned with BYJU’S to learn more about Mitochondria, its structure, and functions.

Practise This Question

Which of the following process is distinctly different from the other three?