Reaktsioonikeskuste

Reaktsioonikeskuste, often translated as "reaction centers," are crucial components in the process of photosynthesis. These specialized protein complexes are embedded within the thylakoid membranes of chloroplasts in plants, algae, and cyanobacteria. Their primary function is to capture light energy and convert it into chemical energy in the form of ATP and NADPH.

There are two main types of reaction centers involved in oxygenic photosynthesis: Photosystem II (PSII) and Photosystem I (PSI). PSII is responsible for the initial absorption of light and the splitting of water molecules, a process known as photolysis. This splitting releases electrons, protons, and oxygen. The electrons are then passed along an electron transport chain. PSI absorbs light at a different wavelength and re-energizes the electrons, which are ultimately used to reduce NADP+ to NADPH.

Within each reaction center, a special pair of chlorophyll molecules, known as the reaction center chlorophylls, play a pivotal role. When these chlorophylls absorb sufficient light energy, they become excited and donate an electron to a primary electron acceptor. This electron transfer initiates a cascade of events that drives the synthesis of ATP and NADPH, the energy currency of the cell, powering the Calvin cycle where carbon dioxide is fixed into sugars.