Biology MITOCHONDRIA, RIBOSOMES, PLASTIDS, MICROBODIES

Mitochondria :

`->` Kolliker (1880) first observed mitochondria as cytoplasmic granules in striped muscles of insects .

`->` Altman (1894) established them as cell organelles and called Bioblast. Flemming and Altman was credited for the discovery of mitochondria. Term 'Mitochondria, was given by C.Benda.

Diameter `0.2 -1.0 mu` m (average `0.5 mu`m)

Length `1.0- 4.1 mu` m

`->` Number `1000-1600` per cell.

`->` Number depends upon physiological activity of cell.

`->` One in Microasterias, Chlorella fusca (alga).

`->` All the mitochondria present in a cell are collectively called chondriome.

`->` Usually plant cells have fewer mitochondria as compared to animal cell.

`->` In higher animals rnaxirnurn mitochondria are found in flight muscles of birds.

`->` Mitochondria can make its shape sausage or cylindrical.

`->` Mitochondria are stained by ,Janus green B.

Structure :

`->` Mitochondria unless specifically stained are not easily visible under the microscope.

`->` Mitochondria is covered by double unit membrane. Outer membrane has more phospholipids (Phosphatidyl choline) and cholesterol as compared to inner membrane. Phospholipid in inner membrane is mainly diphosphatidyl glycerol and Inner membrane have more protein.

`->` The outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e .. the outer compartment and the inner compartment. The inner compartment is called the matrix. The outer membrane forms the continuous limiting boundary of the organelle. The two membranes have their own specific enzymes associated with the mitochondrial function.

`->` Each membrane is `60-75` `A^0` thick and separated by a space (`80-100 A^0`) called perimitochondrial (lntermembrane) space. This space have enzymes required for oxidation of fats. ...

`->` If outer membrane of mitochondria is removed then it is called as mitoplast .

`->` Outer surface of inner membrane is called C- face while inner surface called M- face.

`->` Inner membrane is folded into a number of finger like cristae .

`->` In metabolically active mitochondria number of cristae is higher.

`->` Many electron carrier cylochromes are arran~Jed in a definite sequence in Inner membrane of r,..,.,.,..,..,.,"',."",.'" which forms Electron transport system (ETS).

`->` Inner membrane is studded with pin head particles called oxysomes or elementary particles or `F_(0) - F_(1)` - particles ( `10^4` to `10^6` in number).These particles first described by Fernandez Moran.

`->` Head of Oxysomes or `F_1` is concerned with Oxidative phosphorylation (formation of ATP by energy of oxidation)

`->` Mitochondrial matrix have enzyme for kreb's cycle (Aerobic respiration). Beside these enzymes matrix have a complete
protein synthesis apparatus (Ribosome- (`70`-s). DNA, few RNA's & enzymes) so mitochondria called as semi autonomous cell organelles.


`->` Single, double stranded and circular naked DNA present in mitochondrial matrix.

`->` Mitochondrial DNA is 1% of total DNA in a cell. It is rich in c;-c content.

`->` Mitochondrial DNA can code the synthesis of some types of proteins. Eest of the proteins and enzymes of mitochondria are synthesized under the control of nuclear genes (Semi autonomous nature).

`->` Enzymes for replication and transcription of DNA like DNA- polymer�ase and RNA- polymerase are found
in mitochondrial matrix.

`->` Mitochondria of mammals have 55s ribosomes (35s,25s sub units)

FUNCTIONS OF MITOCHONDRIA:

(1) Mitochondria are site of aerobic respiration.Most of the oxidative metabolism and ATP production occurs in mitochondria, thus mitochondria are the power house of cell, where organic compounds are broken down to release & store metabolic energy in the the form of ATP molecules. (Eesp. metabolism).

(2) Mitochondria help in vitellogenesis in oocytes, Mitochondria of oocytes called Yolk nuclei.

(3) In cytoplasmic inheritance.

Biogenesis Of mitochondria -


 
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