Oxygen as both donor and receiver of electrons?

Question

In mitochondria, NADH supplies electrons to electron transport system. Molecular oxygen is the final receiver. In photosynthesis, oxygen in water is the source of electrons and the final receiver is NADH. How can oxygen be both donor and receiver?

In mitochondria, NADH supplies electrons to electron transport system. Molecular oxygen is the final receiver. In photosynthesis, oxygen in water is the source of electrons and the final receiver is NADH. How can oxygen be both donor and receiver?

Answer 1

H2O does not normally want to release its electrons, its not something that is very easy to do...if you look at the delta G of it, its in the same sort of energy range as visible light, hence the need of light to drive the process
but in normal respiration, O2 loves electrons (just look on the periodic table) and you can see that O2 will attract electrons always without the supply of energy..photosyntheis and respiration are almost identically opposite reactions...quite impressive

Answer 2

The hydrogen in the water is the electron donor, not oxygen. NAD+ accepts the electrons to make the reduced compound NADH