... dioxide is reduced by the addition of electrons provided by NADPH. In order to make glucose from carbon dioxide, the Calvin cycle also utilizes chemical energy from ATP. Pigments aid in the absorption of light. In plants, the main light-absorbing pigments are known as chlorophyll. There are two main types of chlorophyll, chlorophyll a and chlorophyll b. Each type of chlorophyll absorbs different wavelengths of light. Another type of pigment is the carotenoids, pigments in shades of yellow and orange. Carotenoids may broaden the spectrum of colors and absorb light harmful to chlorophyll. When a pigment absorbs the photons, an electron in the pigment "jumps" to a higher energy state. When the electron moves back down to the normal energy state, it emits energy. This concept is important in the light reaction because when electrons move down from a higher energy state, they provide the energy necessary to make ...

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