Electron carriers are molecules that accept and donate electrons during electron transport, facilitating energy transfer. Key examples include NADH and FADH2, which provide electrons to the electron transport chain to produce water and generate ATP. NADH is formed during glycolysis and the Krebs cycle, while FADH2 is exclusively produced in the Krebs cycle.

1. What are electron carriers and what do they do? Provide specific examples and explain where
and how they are used in metabolism.
Solution
Electron carriers are the molecules which are capable of accepting one or two electrons from one
molecule and then donating to the other in the process of electron transport. As the transferring
of electrons occurs from one carrier to other, their energy level decreases and release of energy
occurs.
Ex. Cytochromes, quinones,, NADH, FADH2.
The role of NADH and FADH2 is to donate electrons to the electron transport chain. During the
electron transport chain both NADH and FADH2 donate electronsto create water by providing a
hydrogen molecule to an oxygen molecule to form water. During both the glycolysis and Kreb
cycles NADH is formed as a product. FADH2 is only produced in Krebs cycle.
During the electron transport chain, NADH become NAD+ and the H get transported across the
membrane. Thus in the transport chain electrons reduced from NAD+ are utilised. Similar thing
happens to FADH2 as well. FADH2 becomes FAD+ and the H's are transported across the
membrane. These hydrogens that were released by ATP synthase utilises the hydrogens released
by NAD+ and FAD + to form ATP by placing back hydrogen molecules across the membrane.