chlorofylli

Chlorophylls are a group of closely related green pigments that play a central role in oxygenic photosynthesis. They are magnesium-containing porphyrin compounds with a long hydrophobic phytol tail that anchors them in the thylakoid membranes of chloroplasts in plants and algae, and in the photosynthetic membranes of cyanobacteria.

The most common forms in higher plants and green algae are chlorophyll a and chlorophyll b. Chlorophyll a is the primary pigment involved in the light reactions, while chlorophyll b is an accessory pigment that broadens the range of light that can be absorbed and transferred to chlorophyll a. Other chlorophylls, such as c, d, and f, occur in diverse algae and photosynthetic bacteria and extend absorption into different spectral regions. The characteristic green color arises because chlorophylls absorb light mainly in the blue and red parts of the spectrum and reflect green.

In photosynthesis, chlorophyll molecules are embedded in photosystems I and II within the thylakoid membranes. They absorb photons and transfer excitation energy to reaction centers containing special chlorophyll a molecules (P680 in PS II and P700 in PS I), initiating a sequence of electron transfer that drives the conversion of light energy into chemical energy.

Biosynthesis of chlorophyll occurs in plastids and involves the insertion of Mg2+ into a porphyrin ring, followed by modifications and esterification with phytol to form the mature pigments. Chlorophyll degradation, which occurs during leaf senescence or stress, removes Mg2+ and leads to color changes.

Etymology traces to Greek chloros, green, and phyllon, leaf. Chlorophylls are essential footprints of photosynthetic life on Earth.