The electron transport chain comprises five protein complexes located in the inner membrane of mitochondria.
The components of the electron transport chain are arranged in order of their redox potential, from complex I to IV. The redox potential becomes more positive as we move from the beginning to the end of the chain, indicating that the start of the chain has a more negative redox potential.
This factor drives the movement of electrons along the chain from its starting point to its endpoint. These complexes form a functional unit capable of ATP production. A significant portion of these units are located in the inner membrane of mitochondria.
What are the complexes present in the ETC?
The electron transport chain comprises five protein complexes located in the inner membrane of mitochondria. The components of the electron transport chain are arranged in order of their redox potential, from complex I to IV.
- Complex I (NADH dehydrogenase) contains two prosthetic groups: FMN and Fe-S.
- Complex II (succinate dehydrogenase complex) has two prosthetic groups: FAD and Fe-S. Succinate dehydrogenase is an enzyme that plays a role in the Krebs cycle and the electron transport chain.
- Complex III (ubiquinone-cytochrome c oxidoreductase) has two prosthetic groups: Fe-S and heme.
- Complex IV (cytochrome oxidase) contains two cytochromes, a and a3, and two copper ions.
- Complex V (ATP synthase) in animals has a structure similar to its bacterial and chloroplast counterparts.
ATP synthase consists of two parts, F1 and Fo. The F1 protein is located in the matrix and can be seen as protrusions on the inner membrane. F1 is composed of five different subunits (a3B3y8E). The enzyme’s active site is located on this part of the complex. The FO component consists of three types of proteins: b, a, and c. These hydrophobic subunits are located in the membrane as transmembrane proteins. This pore is exclusive to protons, allowing only proton ions to pass through. Proteins b and A are located on c. The FO part functions to connect 1F to the membrane.
Electron transport chain summary
The electron transport chain (ETC) comprises five protein complexes found in the inner membrane of mitochondria. The components of the electron transport chain are arranged in order of their redox potential, from complex I to IV. Below is a table summarizing the complexes present in the ETC:
| Complex | Prosthetic Groups |
|---|---|
| I | FMN and Fe-S |
| II | FAD and Fe-S |
| III | Fe-S and heme |
| IV | Cytochromes a, a3, and two copper ions |
| V | F1 and Fo |
