WHAT IS CHEMIOSMOSIS AND HOW DOES ATP SYNTHASE FACTOR INTO IT?
Chemiosmosis, in simple terms, is the movement of protons (hydrogen ions, or H+) from the mitochondrial matrix to the intermembrane space across the inner membrane of the mitochondria (in most eukaryotes). In plants, chemiosmosis occurs in the chloroplast, while in prokaryotes, this process takes place in the cell membrane. This movement is enabled by proton pumps embedded within the membrane that allow the hydrogen ions to pass through.
After protons are transferred into the intermembrane space, a proton gradient is formed. This is essentially used to describe the state of having a higher concentration of particles or ions on one side of a membrane than the other; in this case, the intermembrane space has more of these ions than the mitochondrial matrix does due to chemiosmotic process. According to the basic principle of diffusion, particles move from areas of higher concentration to areas of lower concentration. Following this law, the H+ ions flow from the intermembrane space back into the matrix. But wait! What does that do? Weren't the hydrogen ions pumped out as a step in energy production? Of course they were. This is where ATP synthase comes into the picture.
After protons are transferred into the intermembrane space, a proton gradient is formed. This is essentially used to describe the state of having a higher concentration of particles or ions on one side of a membrane than the other; in this case, the intermembrane space has more of these ions than the mitochondrial matrix does due to chemiosmotic process. According to the basic principle of diffusion, particles move from areas of higher concentration to areas of lower concentration. Following this law, the H+ ions flow from the intermembrane space back into the matrix. But wait! What does that do? Weren't the hydrogen ions pumped out as a step in energy production? Of course they were. This is where ATP synthase comes into the picture.
The protons that were pumped into the intermembrane space re-enter the mitochondrial matrix, but not along the same pathway that they exited from. Instead of using the proton pumps, the H+ diffuses through an enzyme embedded in the inner membrane called ATP synthase. As the hydrogen ions flow through a hole in the synthase, something similar to an electrical current forms, generating sufficient energy to spur the synthase to action. With this burst of energy, the synthase is able to attach an inorganic phosphate group to ADP (adenosine diphosphate), forming ATP (adenosine triphosphate). The ATP formed can be used to carry out a variety of different cellular processes, including active transport and mechanical movement (e.g. muscle contraction). Therefore, chemiosmosis and ATP synthesis are the final steps in the formation of one of the most important chemicals necessary in living things. By helping in the production of ATP, chemiosmosis and ATP synthase play an irreplaceable role in the process of cellular respiration and metabolism.
Still confused? Want a broad overview of the overview? Watch the video below to give you a better idea of the bigger picture in chemiosmosis!
Still confused? Want a broad overview of the overview? Watch the video below to give you a better idea of the bigger picture in chemiosmosis!