What is the endpoint of the respiratory chain?

Answer 1

Exhalation!!!
The electron transport chain is a collection of cytochromes and flavoproteins situated close to each other on the inner membrane of the mitochondria. This allows for the proper flow of electrons from one cytochrome to another. A compound such as NADH2 or FPH2 loses hydrogen atoms at the beginning of the chain, returning to its original form, NAD or FP. The electrons pass down the chain of cytochromes, alternately reducing and oxidizing the cytochrome as the electron arrives and moves on to the next one, until finally oxygen is reached and water produced. Hence the process is aerobic, that is, requiring oxygen.

Answer 2

When 2 H+ combine with 1/2 of an O2 molecule producing water.