Functions of Mitochondrion

MITOCHONDRION

Mitochondrion (plural = mitochondria) is a membranebound cytoplasmic organelle concerned with production of energy. It is a rod-shaped or oval-shaped structure with a diameter of 0.5 to 1 μ. It is covered by a bilayered membrane. The outer membrane is smooth and encloses the contents of mitochondrion. This membrane contains various enzymes such as acetyl-CoA synthetase and glycerolphosphate acetyltransferase. The inner membrane is folded in the form of shelf-like

inward projections called cristae and it covers the inner matrix space. Cristae contain many enzymes and other protein molecules which are involved in respiration and synthesis of adenosine triphosphate (ATP). Because of these functions, the enzymes and other protein molecules in cristae are collectively known as respiratory chain or electron transport system.

Enzymes and other proteins of respiratory chain

i. Succinic dehydrogenase

ii. Dihydronicotinamide adenine dinucleotide (NADH) dehydrogenase

iii. Cytochrome oxidase

iv. Cytochrome C

v. ATP synthase.

Inner cavity of mitochondrion is filled with matrix which contains many enzymes. Mitochondrion moves freely in the cytoplasm of the cell. It is capable of reproducing itself. Mitochondrion contains its own deoxyribonucleic acid (DNA), which is responsible for many enzymatic actions. In fact, mitochondrion is the only organelle other than nucleus, which has its own DNA.

Functions of Mitochondrion

1. Production of energy

Mitochondrion is called the ‘power house’ or ‘power plant’ of the cell because it produces the energy required for cellular functions. The energy is produced during the oxidation of digested food particles like proteins, carbohydrates and lipids by the oxidative enzymes in cristae. During the oxidative process, water and carbon dioxide are produced with release of energy. The released energy is stored in mitochondria and used later for synthesis of ATP.

2. Synthesis of ATP

The components of respiratory chain in mitochondrion are responsible for the synthesis of ATP by utilizing the energy by oxidative phosphorylation. ATP molecules diffuse throughout the cell from mitochondrion. Whenever energy is needed for cellular activity, the ATP molecules are broken down.

3. Apoptosis

Cytochrome C and second mitochondria-derived activator of caspases (SMAC)/diablo secreted in mitochondria are involved in apoptosis

4. Other functions

Other functions of mitochondria include storage of calcium and detoxification of ammonia in liver. CENTROSOME AND CENTRIOLES

Centrosome is the membrane-bound cellular organelle situated almost in the center of cell, close to nucleus. It consists of two cylindrical structures called centrioles which are made up of proteins. Centrioles are responsible for the movement of chromosomes during cell division.

SECRETORY VESICLES

Secretory vesicles are the organelles with limiting membrane and contain the secretory substances. These vesicles are formed in the endoplasmic reticulum and are processed and packed in Golgi apparatus. Secretory vesicles are present throughout the cytoplasm. When necessary, these vesicles are ruptured and secretory substances are released into the cytoplasm.

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