Mitochondria,history,Distribution,Morphology,size,shape,number,structure

Mitochondria :

Mitochondria are found in filamentous or granular shape and occurs in all aerobic cell of higher animals and plants and also in certain microorganisms such as Protozoa, Algae, Fungi.

These are absent in bacterial cells.
Mitochondria is the Power House of cell 

History & Identification :

Kolliker: The Mitochondria were first observed by Kolliker in 1850 as a granular structure in the strained muscles.

He named this organelle, the Bioblasts.

Benda: The present The name of Mitochondria was assigned by Benda in 1897-98.

He stained Mitochondria with crystal violet & alizarin.

Palade: Palade described the ultrastructure of cristae(the folding type).

Nass & Nass: In 1963, Nass & Nass demonstrated that the presence of the DNA fibres in the matrix of mitochondria of the embryonic cell.

Attardi, Atlardc, Aloni: They report the 70s type ribosome inside the mitochondria.

Distribution & localization:

The Mitochondria move autonomously in the cytoplasm, so it generally uniform distribution in the cytoplasm, but in many cells, their distribution is very restricted.

The distribution and number of Mitochondria(also mitochondrial cristae) is depending on the function of the cell.

Mitochondrial and its cristae are associated with mechanical and osmotic work situations.

Myocardial muscle cells have a large number of Mitochondria called Sarcosomes , that reflect the great amount of work done by the cells.

Morphology:

Various arrangement of cristae

1.Size:

Normally, Mitochondria is very small in the size 0.5-2.0 um, therefore, are not properly visible under light microscope.

Somewhere their length may reach up to 7 um.

 2.Shape:

The Mitochondria may be filamentous or granular in shape and change one form to another depending upon the physiological condition  of the cell.

Thus, they may be of a club, round, ring, racket, vesicular shape.

3.Number:

The number of Mitochondria in a cell depends on the type and functional state of cell.

Certain cells contain a large number of Mitochondria such as Amoeba, chaos contains 50,000; eggs of sea urchin contain 1,40,000 -1,50,000 and oocytes of amphibians contain 3,00,000 Mitochondria.

Certain cells Viz, liver cells of rat contain only 500- 1600 Mitochondria.

The cells of plants contain less number of Mitochondria comparison to the animal cells because in plants cell the function of Mitochondria is overtake by chloroplast.  

Some algal cell may contain only one Mitochondria.

Structure:

This image from here

Each Mitochondrion is bound by two highly specialized membranes that play a crucial part in its activities.

Outer membrane:

The Mitochondria membrane is 6nm in thickness and fluid-mosaic in ultrastructure.

The outer membrane is quite smooth and has many copies of transport proteins called Porin.

This membrane is permeable of all molecules of 10,000 daltons or less, including small proteins.

Inner membrane:

Inside and separated from the outer membrane by a 6-8nm wide space is present the inner membrane

The inner membrane is not smooth but is impermeable and highly convoluted, forming a series of infolding known as “Cristae”.

The inner membrane has an outer cytosol or c-face toward the peri mitochondrial space & an inner matrix or m-face toward matrix.

For more information:https://www.philpoteducation.com/mod/book/view.php?id=805&chapterid=1076#/

For more information:http://www.biologydiscussion.com/cell-biology/the-size-shape-and-structural-organization-of-mitochondria-membrane/3891

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