Mitochondria
MITOCHONDRIA:-
Mitochondria are cell organelles of aerobic eukaryotes which takepart in oxidative phosphorylation and Krebs cycle of aerobic respiration. They are called power House of the cell because they are the major centres of release energy in the aerobic respiration. They were first observed by kolliker in 1880. Benda gave the present name of mitochondria to the organelles. Mitochondria can be stained differentially with Janus green and are easily distinguishable under light microscope though ultrastructure can be studied only under electron microscope.
Mitochondria absent in prokaryotes and anaerobic eukaryotes. Mitochondria are secondarily lost in the red blood corpuscles of mammals. Their number varies from one to several. The number depends upon cellular activities. Cells of dormant seeds have very few mitochondria
Those of germinating seed have several mitochondria.
Commonly mitochondria are cylindrical in outline. The size of the mitochondria is variable . Normally they have a length of 1.0-4.1 micrometer and diameter of 0.2-1.0 micro meter .
ULTRASTRUCTURE OF MITOCHONDRIA:-
A mitochondria contains two membrane and two Chambers ,outer and inner . The two membranes form the envelope of the mitochondrion. Each of them is 60-70 Armstrong in thickness.
Outer membrane :- The membrane is smooth. It is permeable to a number of metabolites . It is due to presence of protein channels called porins or minute pores. A few enzymes connected with lipid synthesis are located in the membrane . It is poorer in proteins as compared to inner membrane .
Inner membrane:- It is permeable to only some metabolites. It is Rich in double phospholipid called cardiolipin which make the membrane impermeable to ions. Proteins content is also high ,being 70-75% of total components. The inner membrane is infolded variously to form involutions called cristae. They meant for increasing the physiologically active area of the inner membrane. The cristae are generally arranged like baffles,at right angles to the longitudinal axis of the mitochondrion.
The inner membrane as well as it's cristae posses small tennis racket like particles called elementary particles or oxysome or F0-F1 particles. Each oxysome has a head,a stalk and a base . The base is about 11nm long and 1.5nm in thickness. The stalk is about 5nm long and 3.5 nm broad . The head has diameter of 8.5nm. Oxysome function as ATP-ase . They are,therefore ,the centres of ATP synthesis during oxidative phosphorylation.
ANATOMY OF MITOCHONDRIA:-
1) Mitochondria have their own DNA which can replicate independently
2) Mitochondrial DNA produce it's own mRNA,tRNA,and rRNA .
3)The organelles posses their own ribosomes.
4) Mitochondria synthesise some of their own structural proteins.However,most of the Mitochondrial proteins are synthesised under instructions from cell nucleus.
5)The organelles synthesise some of the enzymes required for their functioning.
6)They grow internally.
7) New Mitochondria develop by division /binnary fission of pre existing mitochondria.
Mitochondria are cell organelles of aerobic eukaryotes which takepart in oxidative phosphorylation and Krebs cycle of aerobic respiration. They are called power House of the cell because they are the major centres of release energy in the aerobic respiration. They were first observed by kolliker in 1880. Benda gave the present name of mitochondria to the organelles. Mitochondria can be stained differentially with Janus green and are easily distinguishable under light microscope though ultrastructure can be studied only under electron microscope.
Mitochondria absent in prokaryotes and anaerobic eukaryotes. Mitochondria are secondarily lost in the red blood corpuscles of mammals. Their number varies from one to several. The number depends upon cellular activities. Cells of dormant seeds have very few mitochondria
Those of germinating seed have several mitochondria.
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| (Structure of mitochondria) |
Commonly mitochondria are cylindrical in outline. The size of the mitochondria is variable . Normally they have a length of 1.0-4.1 micrometer and diameter of 0.2-1.0 micro meter .
ULTRASTRUCTURE OF MITOCHONDRIA:-
A mitochondria contains two membrane and two Chambers ,outer and inner . The two membranes form the envelope of the mitochondrion. Each of them is 60-70 Armstrong in thickness.
Outer membrane :- The membrane is smooth. It is permeable to a number of metabolites . It is due to presence of protein channels called porins or minute pores. A few enzymes connected with lipid synthesis are located in the membrane . It is poorer in proteins as compared to inner membrane .
Inner membrane:- It is permeable to only some metabolites. It is Rich in double phospholipid called cardiolipin which make the membrane impermeable to ions. Proteins content is also high ,being 70-75% of total components. The inner membrane is infolded variously to form involutions called cristae. They meant for increasing the physiologically active area of the inner membrane. The cristae are generally arranged like baffles,at right angles to the longitudinal axis of the mitochondrion.
The inner membrane as well as it's cristae posses small tennis racket like particles called elementary particles or oxysome or F0-F1 particles. Each oxysome has a head,a stalk and a base . The base is about 11nm long and 1.5nm in thickness. The stalk is about 5nm long and 3.5 nm broad . The head has diameter of 8.5nm. Oxysome function as ATP-ase . They are,therefore ,the centres of ATP synthesis during oxidative phosphorylation.
ANATOMY OF MITOCHONDRIA:-
1) Mitochondria have their own DNA which can replicate independently
2) Mitochondrial DNA produce it's own mRNA,tRNA,and rRNA .
3)The organelles posses their own ribosomes.
4) Mitochondria synthesise some of their own structural proteins.However,most of the Mitochondrial proteins are synthesised under instructions from cell nucleus.
5)The organelles synthesise some of the enzymes required for their functioning.
6)They grow internally.
7) New Mitochondria develop by division /binnary fission of pre existing mitochondria.
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