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-harvesting complexes of green plants protons and electrons. Under changing light conditions, the reversible phosphorylation of light harvesting chlorophyll a/b binding proteins (LHCII) represents a system for balancing the excitation energy between the two photosystems. The N-terminus of the chlorophyll A-B binding protein extends into the stroma where it is involved with adhesion of granal membranes and photo-regulated by reversible phosphorylation of its threonine residues. Both these processes are believed to mediate the distribution of excitation energy between photosystems I and II. This family also includes the photosystem II protein PsbS, which plays a role in energy-dependent quenching that increases thermal dissipation of excess absorbed