Question

Explain how the “slide” of electrons down the electron transport chain is coupled to the production of ATP by chemiosmosis.

Answer 1

during electron transport chain NADH and FADH2 is oxidized via complexes on the electron transport chain.

NADH is oxidized by complex I, from complex I electrons are transferred to co-enzyme Q, complex III oxidizes coenzyme Q and reduces cytochrome c, cytochrome c is oxidized by complex IV and oxygen is reduced at complex IV.

FADH2 is oxidized by complex II, from complex II electrons are transferred to co-enzyme Q, complex III oxidizes coenzyme Q and reduces cytochrome c, cytochrome c is oxidized by complex IV and oxygen is reduced at complex IV.

as the electrons move down the electron transport chain, from a species with lower reduction potential to a species with higher reduction potential, energy is released, using the energy released H+ from the matrix is pumped to the intermembrane space creating an H+ gradient.

H+ gradient across the inner mitochondrial membrane is used by the ATP synthase, ATP synthase transports H+ down the concentration gradient to the mitochondrial matrix, during this process energy is released and ATP synthase rotates, then the mechanical energy is converted to chemical energy between the anhydride bonds between phosphate groups in ATP ( ATP is made from ADP and Pi).

The movement of H+ ions down the concentration gradient is chemiosmosis.

So the electron transport chain is coupled to ATP synthesis by chemiosmosis.