Is the passage of protons through the ATP synthase exergonic or endergonic? Explain how the passage of protons through this enzyme relates to ATP synthesis
The correct answer and explanation is:
The passage of protons through the ATP synthase is exergonic. This means that it releases energy as protons move down their electrochemical gradient. This process is crucial for ATP synthesis in cellular respiration.
ATP synthase is a membrane-bound enzyme complex located in the inner mitochondrial membrane (in eukaryotes) or the plasma membrane (in prokaryotes). It operates based on a proton gradient created by the electron transport chain (ETC). In the ETC, high-energy electrons move through protein complexes, and as they do, protons are pumped across the membrane from the mitochondrial matrix to the intermembrane space, establishing a proton gradient and an electrochemical potential difference (also called proton motive force, or PMF).
As protons flow back into the mitochondrial matrix through the ATP synthase complex, the passage is exergonic because the energy stored in the proton gradient is released. This movement drives the rotation of part of the ATP synthase enzyme, specifically the F0 unit, and induces conformational changes in the F1 unit. These conformational changes allow ADP and inorganic phosphate (Pi) to bind, undergo phosphorylation, and form ATP.
The process of proton movement through ATP synthase is called chemiosmosis, and it couples the exergonic flow of protons to the endergonic process of ATP synthesis. Essentially, the energy released by the proton gradient is used to power the production of ATP from ADP and phosphate. This process is essential for providing the cell with usable energy. Without ATP synthase and chemiosmosis, cells would not be able to efficiently produce ATP, limiting their ability to perform necessary biological functions.