Best note ||For class11 ||Describe the structure of mitochondria in detail?
Introduction:
A mitochondria is a membrane bound , bean shaped organelle.
The word mitochondrion , derived from the Greek word mitos which means thread,and chondrion which means grain like.
The diameter of these organelles varies from 0.5-1micrometer.
As mitochondria generate most of the cell's supply of ATP ,which help to provide chemical energy, therefore it is sometimes regarded as the ''cellular power plants''.
Depending upon the organism and tissue type,the number of mitochondria in a cell varies widely.
It is seen that many cells have only a single mitochondrion whereas other cells can contain several thousand mitochondria.
Kolliker the scientist, who first observed mitochondria in the year of 1850 ,as granular structure in the striated muscle.
⏺️ Structure of mitochondria:
There are two types of membranes present in mitochondria first one is outer membrane and second one is inner membrane,and they are composed of proteins and phospholipid bilayer.
Because of the presence of, this type of double membrane structure, there is present five distinct parts to a mitochondrion.
These are:
1.Outer membrane of the mitochondria.
2.The intermembrane space (which is present in between the outer and inner membrane).
3.The inner membrane of the mitochondria.
4.The cristae.
5.And the matrix.
OSC Microbio 03 04 Mitochond.jpg, Image by-CNX OpenStax , Source , License-CC BY4.0
1.Outer membrane of mitochondria :
The outer mitochondrial membrane completely encloses the mitochondria ,and in it present a protein to phospholipid ratio similar like the eukaryotic plasma membrane.
The outer membrane of the mitochondria contains a type of transport protein, called porins.
which helps in the formation of large aqueous channels through the lipid bilayer.
These channels allow those molecules, to move freely from one side of the membrane to the other ,which contains 5000 Daltons or less than that molecular weight.
Large protein can enter the mitochondrion If a signalling sequence at the N -terminus binds to a large multi subunit protein known as translocase of the outer membrane, which then helps then to move across the membrane.
➡️ The outer membrane of the mitochondria can associate with the membrane of the endoplasmic reticulum, helps in the formation of MAM(mitochondria associated ER membrane).
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2. The intermembrane space of Mitochondria:
➡️The intermembrane space is the space which is present in between the outer and inner mitochondrial membrane.It is also known as the perimitochondrial space.
➡️ The protein composition in the inter membrane space is different from the protein composition which is present in the cytosol.
3.The inner mitochondrial membrane.
➡️The inner membrane of the mitochondria is highly specialized in nature.
➡️There's present more than 151 different types polypeptides in the inner mitochondrial membrane.Its lipid bilayer is made up of a high proportion of the double phospholipid namely cardiolipid.
➡️In cardiolipid there is present four fatty acids rather than two, and many of them are involved to make the membrane , especially impermeable to ions.
➡️ The inner mitochondrial membrane contains protein with five types of functions
.ATP synthase , which helps in the formation of ATP in the matrix.
. Protein transport machinery
. Mitochondrial fusion and fission protein.
. Specific transport protein that regulate the metabolic passage into or out of the matrix.
4.Cristae :
➡️The inner membrane of the mitochondria is highly folded into winding like structure , with a great deal of surface area, which is known as cristae . Cristae project into the matrix.
➡️The number of cristae present in the mitochondrion of the cardiac muscle is three times greater than that of mitochondrion present in a liver cell.
There is present many enzymes in the cristae and also other protein molecules which are involves in the synthesis of ATP and in the process of respiration.
Because of these types of functions the enzymes and other protein molecules present in the cristae of the mitochondria are collectively known as respiratory chain or electron transport system.
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5.Matrix
➡️The matrix of the mitochondria are homogeneous,dense,gel like proteinaceous structure.
➡️ It is surrounded by the inner membrane of the mitochondria . Most of the protein which are present mitochondrion are present in the matrix (about 2/3rd).
➡️ The matrix of the mitochondria contain lipids, ribosomes (55s), circular DNA molecules , proteins etc.
➡️The matrix of the mitochondria has an important role in the production of Adenosine Tri Phosphate, with the help of ATP synthase, which is present in the inner membrane of the mitochondria.
In the matix there is also present a highly concentrated mixture of hundreds of enzymes.
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Very informative 👍👍
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