What is the electron transport chain?

The electron transport chain (ETC) is the final stage of aerobic respiration where high-energy electrons from NADH and FADH₂ are transferred through a series of proteins to produce a large amount of ATP.

It occurs in the inner mitochondrial membrane and is the main site of energy production in cells.

How the electron transport chain works:

1. Transfer of electrons
NADH and FADH₂ donate high-energy electrons to the electron carriers (protein complexes) in the membrane.

2. Energy release and proton pumping
As electrons move through the chain, energy is released and used to pump hydrogen ions (H⁺) across the membrane, creating a proton gradient.

3. Formation of ATP (chemiosmosis)
Hydrogen ions flow back through an enzyme called ATP synthase, and this movement drives the production of ATP from ADP.

4. Role of oxygen
Oxygen acts as the final electron acceptor, combining with electrons and hydrogen ions to form water (H₂O). Without oxygen, the chain stops.

Energy yield:

• Produces the majority of ATP during respiration (around 32–34 ATP per glucose)

Importance:

• Most efficient stage of respiration

• Essential for high energy output

• Maintains continuous ATP supply for cells

In simple terms: The electron transport chain uses electrons to create a proton gradient that powers the production of large amounts of ATP.