Question

How does an electron transport chain work?

Answer 1

How does an electron transport chain work?

As the electrons from reduced molecules such as NADH and FADh are passed through the complexes to the final acceptor oxygen, the protons are pumped across the inner membrane to intermembrane space of the mitochondria. This generates proton motive force. Protons flow back to the mitochondrial matrix through ATP synthase forming ATP.

Steps involved are

Step 1 Two electrons are passed from NADH into the NADH dehydrogenase complex. Coupled with this transfer is the pumping of one hydrogen ion for each electron.

Step 2 The two electrons are transferred to ubiquinone.

Step 3 Each electron is then passed from the cytochrome b-c1 complex to cytochrome c. One hydrogen ion is pumped through the complex as each electron is transferred.

Step 4 The next major step occurs in the cytochrome oxidase complex. This step requires four electrons. These four electrons interact with a molecular oxygen molecule and eight hydrogen ions. The four electrons, four of the hydrogen ions, and the molecular oxygen, are used to form two water molecules. The other four hydrogen ions are pumped across the membrane.

Step 5 The hydrogen pumping steps creates a gradient. The potential energy in this gradient is used by ATP synthase to form ATP from ADP and inorganic phosphate.

This is analogous to how a hydroelectric dam functions. The water at the top of dam or falls has higher potential energy that that of the water at the base of the dam/falls. As the water falls down, some of the potential energy of the water is harnessed to drive turbines that make electricity.