Photosynthesis that leads to the ultimate reduction of NADP to NADPH. In addition, this creates a proton gradient (energy gradient) across the chloroplast membrane, which is used by ATP synthase in the synthesis of ATP. The chlorophyll molecule ultimately regains the electron it lost when a water molecule is split in a process called photolysis, which releases a dioxygen (O) molecule as a waste product. The overall equation for the light-dependent reactions under the conditions of non-cyclic electron flow in green plants is: Not all wavelengths of light can support photosynthesis. The photosynthetic action spectrum depends on the type of accessory
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