Behavior of mitochondria in the living cell.

Publisher Summary This chapter describes the behavior of mitochondria in the living cell. The dynamics of mitochondria during fusion and fission and in intracellular displacement have important implications for understanding the supramolecular organization of cytoplasm. The physiological significance of the formation of mitochondrial reticula and the location of mitochondria close to energy-consuming structures is clear, and active locomotion establishes and maintains these important associations. Fusion and fission is of genetic significance, allowing the rapid exchange of alleles among different strands of DNA and thus accelerating the spreading of new mutations through a population of mitochondria. It also stabilizes the mitochondrial genome by facilitating recombinations and eliminating mutations. Fusion and fission of mitochondria also provide a structural control mechanism within the cell, allowing adaptation to varying energy demands during differentiation processes. A mitochondrial reticulum forms a pathway for energy transduction, which is equivalent to other transport systems such as cytoplasmic streaming or electrotonic signal transduction in some nerve cells. The role of supramolecular organization within the cytoplasm and the resulting microcompartmentation of the cell are necessary to elucidate these mechanisms.