Final answer:
The chemiosmotic theory proposes that ATP synthesis is driven by a proton gradient created by an electron transport chain across a membrane. As protons flow back through ATP synthase, their energy is harnessed to produce ATP from ADP. This theory is central to understanding energy conversion during cellular respiration and photosynthesis.
Step-by-step explanation:
The chemiosmotic theory is a principle in bioenergetics that explains how ATP is synthesized in the mitochondria and chloroplasts of cells. Peter Mitchell, the Nobel Prize-winning biochemist, introduced this concept to elucidate the mechanism of ATP synthesis in cellular respiration and photosynthesis. According to this theory, an electron transport chain creates a proton gradient across a membrane, leading to the flow of protons back through the ATP synthase enzyme. This flow provides the energy necessary for the conversion of ADP to ATP. The remarkable aspect of this mechanism is its universal application across many forms of life to effectively convert energy from food and light into the molecular energy currency of the cell, ATP.
During the process of oxidative phosphorylation, which occurs in the mitochondria, electrons are transported through a series of complexes that drive the pumping of protons from the mitochondrial matrix to the intermembrane space. This creates an electrochemical gradient. When the protons flow back into the matrix through ATP synthase, their potential energy is transformed into chemical energy, which is utilized to phosphorylate ADP into ATP. The creation of water from oxygen and low-energy electrons at the end of the electron transport chain rounds off the process. The chemiosmotic mechanism is integral not only to cellular respiration but also to the light reactions of photosynthesis where it's referred to as photophosphorylation.