The formation of trans-thylakoid proton motive force (pmf) is coupled to light-driven electron transfer and both powers the synthesis of ATP and acts as a signal for initiating antenna regulation. This key intermediate has been difficult to study because of its ephemeral and variable qualities. This review covers recent efforts to probe pmf in vivo as well as efforts to address one of the key questions in photosynthesis: How does the photosynthetic machinery achieve sufficient flexibility to meet the energetic and regulatory needs of the plant in a varying environment? It is concluded that pmf plays a central role in these flexibility mechanisms.
All of the sugar produced in the photosynthetic cells of plants and other organisms is derived from the initial chemical combining of carbon dioxide and water with sunlight.
LabBench Activity Plant Pigments and Photosynthesis
Higher plants, phytoplankton, algae, as well as some bacteria carry out the process of photosynthesis.
Steps of Photosynthesis
Photosynthesis occurs in two main stages, the first stage being towards light reaction and the second stage being the Calvin Benson Cycle.
These also produce a proton gradient, ..
Photophosphorylation is the production of ATP using the energy of sunlight. Photophosphorylation is made possible as a result of chemiosmosis. Chemiosmosis is the movement of ions across a selectively permeable membrane, down their concentration gradient. During photosynthesis, light is absorbed by chlorophyll molecules. Electrons within these molecules are then raised to a higher energy state. These electrons then travel through Photosystem II, a chain of electron carriers and Photosystem I. As the electrons travel through the chain of electron carriers, they release energy. This energy is used to pump hydrogen ions across the thylakoid membrane and into the space within the thylakoid. A concentration gradient of hydrogen ions forms within this space. These then move back across the thylakoid membrane, down their concentration gradient through ATP synthase. ATP synthase uses the energy released from the movement of hydrogen ions down their concentration gradient to synthesise ATP from ADP and inorganic phosphate.