Question

22: What are the unique characteristics of mitochondrial inner membrane that contribute to its function?

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Answer 1

Mitochondria are regarded as powerhouse of the cell. Inner mitochondrial membrane lies between the outer membrane and mitochondrial matrix. It is folded extensively with numerous invaginations called as cristae which are seperated by crista junctions. This highly folded and compartmentalized structure of the membrane increases its total surface area to a great extent. The first compartment is the space between the inner and outer membrane of mitochondria is called the intermembrane space and is continuous with cytosol, and the second compartment is the more convoluted space at the inside part of the inner membrane, called matrix. These compartments seperate the matrix from the cytosolic environment.

Respiratory chain complexes reside in the cristae of inne mitochondrial membrane. Cristae membranes are the sites for F1 protein complexes to act and plays an important role in proton-gradient driven ATP synthesis in the mitochondria. Mitochondrial F1-Fo ATP synthase is the protein complex in the cristae. The highly folded structure gives a larger surface area for protein complexes to act efficiently. Junctions seperates the cristae and the inner boundary membranes. For mitochondria to function efficiently, the inner membrane is fully permeable to oxygen, carbon dioxide, and water. Since it is less permeable to ions and small molecules, it acts as an efficient chemical barrier. Ions can enter from cytosol only with the help of specilaized ion transporters located on the inner membrane.