Question

Can ATP synthase work without a proton gradient?

Answer 1

ATP

1. ATP stands for Adenosine 5′-triphosphate.
2. It is an energy molecule present in all living organisms, commonly referred to as an energy currency.
3. Act as a coenzyme that works with enzymes. For example ATP triphosphates to transfer energy to cells by releasing its phosphate groups.
4. ATP molecule consists of three components, Adenine bicyclic system, a furanose, and a triphosphates chain.

Proton Gradient

1. The proton gradient is a product of the electron transport chain produced by proton pumping.
2. The proton gradient is important for ATP synthesis.
3. ATP synthesis requires a proton gradient during the electron transport chain inside the matrix of mitochondria.
4. The energy which is obtained from the passage of electrons through the electron transport chain is used to transport protons across the inner mitochondrial membrane.
5. Four protons entering an elementary particle knock out one oxygen of phosphate making its energy-rich reactive phosphate for combining with ADP.
6. So without a proton gradient ATP synthesis can't work.

Electron Transport Chain

1. The electron transport chain (ETC) is an important metabolic pathway that produces energy by performing a series of redox reactions that transfer electrons from electron donor to electron receptor.
2. ETC also involves the transfer of protons (H ions) through the membrane.
3. This series leads to the development of a gradient of electrochemical protons across the membrane which activates the ATP synthase proton pump, resulting in the generation of ATP (energy) molecules.
4. The ETC cycle ends up with the absorption of electrons by oxygen molecules.
5. A cycle of the electron transport chain produces around 30 molecules of ATP (Adenosine triphosphate)
6. In eukaryotic organisms, the electron transport chain incorporated in the inner membrane of the mitochondria
7. In bacteria, ETC is found in the cell membrane. In plants, it is present in the thylakoid membrane of the chloroplasts. In chloroplast photons from light are used to generate a proton gradient.

Enzyme Complexes used in Electron Transport Chain

1. Complex I NADH-coenzyme Q oxidoreductase: First NADH is oxidized to NAD+ by reducing FMN to FMNH2 in a two-step electron transfer. FMNH₂ is then oxidized to FMN where the two electrons are first transferred to Fe-S centers and then to ubiquinone.
2. Complex II NADH-coenzyme Q oxidoreductase: The enzyme complex catalyzes the transfer of electrons from other donors like fatty acids and glycerol-3 phosphate to ubiquinone through FAD and Fe-S centers. The enzyme complex catalyzes the transfer of electrons from other donors like fatty acids and glycerol-3 phosphate to ubiquinone through FAD and Fe-S centers.
3. Complex III Q-cytochrome c oxidoreductase: The enzyme complex, cytochrome reductase, catalyzes the transfer of two electrons from reduced CoQH₂ to two molecules of cytochrome c. Meanwhile, the protons (H⁺) from the ubiquinone are released across the membrane aiding the proton gradient. The CoQH₂ is oxidized back to CoQ while the iron center (Fe³⁺) in the cytochrome c is reduced to Fe²⁺.
4. Complex IV cytochrome c oxidase: Complex IV have of cytochrome a and a3 and is known as cytochrome oxidase. This is the last complex of the electron transport chain and is involved in the transfer of two electrons from cytochrome c to molecular oxygen (O2) forming water. At the same time, four protons are translocated across the membrane aiding the proton gradient.