Mitochondria Structure and Function

  • Morphology: No. of mitochondria depends on cell type and functional state of cell
  • Size: 0.5-2.0 µm
  • double membrane organelle
  • Outer membrane with porin proteins (transport proteins) , permeable
  • Inner membrane with infoldings called cristae , less permeable, presence of cardiolipin
  • Mitochondrial matrix: proteins 65-70%, lipids 25-30%, 0.5% RNA and circular DNA molecule
  • Microscopic observation: Janus Green stain-stains living mitochondria greenish blue.
  • Inner membrane: site of oxidative phosphorylation and electron transport and associated ATP production.
  • Central matrix: site of citric acid cycle and fatty acid break down and mt DNA codes some mt proteins.
Histochemical/ cytochemical markers:
  • monoamine oxidase for outer membrane
  • Cytochrome oxidase for inner membrane
  • Malate dehydrogenase for matrix
Similarity between mitochondria and prokaryotes
(that supports Endosymbiont theory)
Endosymbiont theory
  • The bacterial plasma membrane resembles the inner mitochondrial membrane in many aspects. Bacterial plasma membrane has infolding called mesosomes.
  • Circular ds DNA
  • Not covered by a membrane
  • Not associated with histone proteins
  • Generally lack introns
  • Small 70 S ribosomes
  • Protein synthesis initiated by formyl methionyl tRNA (f-met tRNA) and in both mitochondria and bacteria protein synthesis can be inhibited by the same inhibitor chloramphenicol
  • Replication, transcription and translation similar to bacteria.
  • And high degree of relatedness between mt genes and bacterial genes
Learn more :Mitochondrial genome (mt DNA)
Previous Post Next Post