Chlorophyll a chlorophyll biosynthesis. Chlorophyll "a" absorbs light within the violet, blue and red wavelengths while mainly reflecting green. This reflectance gives chlorophyll its green appearance. Accessory photosynthetic pigments broaden the spectrum of light absorbed, increasing the range of wavelengths that can be used in photosynthesis. The addition of chlorophyll "b" next to chlorophyll "a" extends the absorption spectrum. In low light conditions, plants produce a greater ratio of chlorophyll "b" to chlorophyll "a" molecules, increasing photosynthetic yield. Absorption of light by photosynthetic pigments converts photons into chemical energy. Light energy radiating onto the chloroplast strikes the pigments in the thylakoid membrane
Light-dependent reactions poorly understood structure embedded within PS II called the "water-splitting complex" or the "oxygen-evolving complex". It catalyzes a reaction that splits water into electrons, protons and oxygen: 2 → 4H + 4e + The actual steps of the above reaction are running in the following way (Dolai's diagram of S-states): The electrons are transferred to special chlorophyll molecules (embedded in PS II) that are promoted to a higher-energy state by the energy of photons. The excitation P680 → P680of the reaction center pigment P680 occurs here. These special chlorophyll molecules embedded in PS II absorb the energy of photons, with