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
Carotenoid especially reds and purples, are due to other classes of chemicals. Carotenoids serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage. Carotenoids that contain unsubstituted beta-ionone rings (including beta-carotene, alpha-carotene, beta-cryptoxanthin and gamma-carotene) have vitamin A activity (meaning that they can be converted to retinol), and these and other carotenoids can also act as antioxidants. In the eye, lutein, meso-zeaxanthin, and zeaxanthin are present as macular pigments whose importance in visual function remains under clinical research in 2017. The basic building blocks of carotenoids are isopentenyl diphosphate