The Mitochondrial Free Radical Theory of Aging - Supernova: Pliki

A Challenge from Textbook Bioenergetics and Free Radical Chemistry
to cross between surface and bulk, thus reducing the surface-to-surface proton-motive
force (∂p) and impairing OXPHOS. It has indeed been shown 49 that the degree to which
proton conduction is preferentially lateral varies with the density of negatively charged
head groups.
This idea is too new to have undergone the detailed analysis by the bioenergetics
community that will be needed before it can be accepted as a valid refinement of the
chemiosmotic theory. I anticipate that such scrutiny will be intensive, because the
ramifications of this model for our understanding of mitochondrial function are very
profound. For example, one vital role of mitochondria in vivo is cellular calcium homeostasis:
they are able to take up and store calcium when there is an excess of it in the cytosol, so
stabilising its cytosolic concentration. The textbook model for how they achieve this relies
on the presence of a large bulk-to-bulk Δψ, which causes cations (of which calcium in solution
is of course one) to leak, slowly, through the mitochondrial membrane. If there is in fact no
Δψ, that mechanism must be radically revised.
Presuming that this model survives such scrutiny, however, it finally shows—after a
whole chapter of twists and turns—that SOS is, after all, compatible with the rise in superoxide
levels that is caused by certain types of respiratory chain inhibition.
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