Mitochondria Introduction Structure and Functions
- Mitochondria word from greek word Mitos – thread; Chondrion – granule.
- First seen by kolliker in striated muscles of insects.
- Term mitochondria was given by Benda.
- Fleming gave them name filla.
- Altman considered them cell organelle and called them bioplast.
- It is called power house of cell.
- It is maternal inheritance or cytoplasmic inheritance.
- Cells with more metabolic activity have more number of mitochondria.
- Generally their number is 1000-1600 in a cell.
- In ova, number of mitochondria increase in order to increase.
- Prokaryotic cell, anaerobic cells and old mammalian RBCs lack
- Microsterias green alga and sporozoite have one mitochondria.
- Chaos Chaos amoeba and pleomyxa have 5 lac mitochondria.
- Animal cell have more mitochondria than plant cell.
Typically it is sausage-shaped or cylindrical or rod like or filamentous having a diameter of 0.2-1.0µm and length 1.0-4.1µm.
Mitochondria is a double membrane structure having following components –
(A) Outer membrane:-
- Outer membrane of mitochondria transfer very large molecules about 6000 kD.
- It has more Phosphatidyl choline.
- It enclose entire organelle made up of protein and phospholipid in ratio 1:1 by weight.
- It consists of large number of integral proteins called porins. So more permeable than inner membrane.
- It can associate with E.R. it is 60-70 Å thick.
- It has stalk less particles on outer surface known as subunits of parson.
(B) Perimitochondrial space: –
- It is of 80-100Å size.
(C) Inner membrane: –
- These perform redox reactions of oxidative phosphorylation.
- ATP synthesis.
- Transport protein.
- Protein import machinery.
–> Outer surface of inner membrane is known by as C-face while inner surface is called M-face.
- Inner membrane possess many projection called cristae.
- Cristae contains with small round bodies called F2 particles or oxysomes or inner membrane subunit.
- At the base of F2 particle, factor F0 is present which helps in attachment of F1 particle with inner membrane and called as OSCP (oligomycin sensitivity conferring protein).
- Distance between two oxysomes is 100Å.
- Oxysomes are made up of ATPase enzyme and are related with oxidative phosphorylation.
- It is a space enclosed by inner membrane. It contain about 2/3 of the total protein a mitochondrion.
(E) Inner chamber: –
- It contains fluid knows as matrix.
- It consists of mixture of large number of Krebs cycle enzyme, special mitochondrial ribosomes, t-RNA and several copies of the mitochondrial DNA genome.
(F) Mitochondrial DNA: – .
- It constitute 1% of total DNA of cell.
- Size of mt-DNA is greater in plant than animals.
- In mitochondria genome size is small but gene no is very high.
- Mitochondrial genome size in human is 16kD and yeast 200kD
- Mutation in mt-DNA produce Labour Optic Neuropathy. In this neuron connected with optic nerve get damaged.
- DNA is double stranded, naked granular, circular, molecule with higher G-C ratio.
- Mt-DNA is used for the study of Phylogenetic relationships.
- It have 70s type Ribosomes.
- It is called semi-autonomous bodies because of presence of mitochondrial DNA (m-DNA) in them
- Cellular respiration and ATP production.
- ATP storage and transport
- Vitellogenesis – mitochondrial kinase makes yolk dense and insoluble. Mitochondria are also called yolk nuclei in egg.
- It found in neurons where they help to from neurohormone. Rg. Acetylcholine.
Mitochondria is similar to rickettsia bacteria
Mitoplast- if outer membrane of mitochondria is removed then it called mitoplast. After it mitochondria can work.
Similarities between plastids and mitochondria: –
- Both exhibit similar growth and origin.
- Both are able to synthesize their own required protein.
- It is believed that both are evolved from endosymbiotic bacteria.
Programmed Cell Death: –
When mobile electron carrier (Cyt-c) comes into the cytoplasm it is a signal of programmed cell death. In cytoplasm Cyt-c bind to APAF by procaspases and cell undergo to death.
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