Electron Transport Chain

Electron Transport Chain

• As electrons are removed from a molecule of Glucose, they carry much energy that was originally stored in their chemical bonds.

• These electrons are transferred to readied hydrogen carrier molecules.

• In the case of Cellular Respiration, these charged carriers are the coenzymes NADH and FADH2.

• We now have:

  • 2 NADH molecules from Glycolysis

  • 2 NADH from the production of acetyl-CoA

  • 6 NADH from The Krebs Cycle

  • 2 FADH2 from The Krebs Cycle

• That gives us a total of 12 electron or energy carriers altogether.

• These electron carriers—NADH and FADH2—“shuttle” electrons to the electron transport chain, the resulting NAD+ and FADH can be recycled to be used as carriers again, and the hydrogen atoms are split into hydrogen ions and electrons.

• The high-energy electrons from NADH and FADH2 are passed down a series of protein carrier molecules that are embedded in the cristae; thus, it is called the electron transport chain.

• Some of the carrier molecules in the electron transport chain are NADH dehydrogenase and cytochrome C.

• Each carrier molecule hands down the electrons to the next molecule in the chain.

• The electrons travel down the electron transport chain until they reach the final electron acceptor, oxygen. Oxygen combines with these electrons (and some hydrogens) to form water.

• This explains the “aerobic” in aerobic respiration. If oxygen weren’t available to accept the electrons, they wouldn’t move down the chain at all, thereby shutting down the whole process of electron transport.

Electron Transport Chain

The Electron Transport Chain (ETC) is a series of proteins embedded in the Thylakoid membrane that transfer electrons during the Light-Dependent Reactions. As electrons move through the chain, energy is released and used to pump protons from the Stroma into the Thylakoid Lumen, creating a Proton Gradient. Key components include Plastoquinone (PQ), the Cytochrome Complex, and Plastocyanin (PC). The ETC links Photosystem II to Photosystem I, enabling ATP and NADPH production for the Calvin Cycle.