Structures and properties of pigment molecules

(a) The structure of chlorophylls a and b. As indicated, chlorophylls a and b differ only at a single site, at which chlorophyll a has a ?CH3 group and chlorophyll b has a ?CHO group. (b) The structure of ?-carotene, an example of a carotenoid. The shaded areas are the regions where a delocalized electron can hop from one atom to another. (c) Absorption spectra that show the absorption of light by chlorophyll a, chlorophyll b, and ?-carotene. (d) An action spectrum of photosynthesis depicting the relative rate of photosynthesis in green plants at different wavelengths of light.