Question

correlate the length of an ETC and the carriers in it with the magnitude of the proton motive force it generates.

Answer 1

The electron transport chain contains several components.
1. A semi-permeable membrane
2. Electron donor
3. Electron carriers
4. Electron acceptors
5. ATP synthase complex

The flow of electrons through electron carriers results in the pumping of protons across the membrane generating the proton gradient. This proton gradient is coupled to ATP synthesis by the ATP synthase complex.

If the length of ETC is longer, it can accommodate more electron carriers and can pump more protons across the membrane. As a result, more ATP can be produced.
i.e. there is a positive correlation between the length of ETC and the number of electron carriers to that of ATP yield.