Chlorophyll’s function in plants is to absorb light and transfer it through the plant during photosynthesis. The chlorophyll in a plant is found on the thylakoids in the chloroplasts.
Chlorophyll uses sunlight to make sugar. It’s the key substance within chloroplasts, which are the food production centers of a plant cell. Sunlight hitting chloroplasts in plants is absorbed by chlorophyll and then combined with carbon dioxide and water to create glucose, or sugar. This process also creates oxygen, which animals use in their own respiration. Mitochondria then use the sugar produced by the chlorophyll to convert it into energy that’s usable by the plant. The stroma regulate the carbon dioxide intake of the plant, which is critical to the whole process.
Chlorophyll is also not the only structure that uses light. Algae has phycoerythrin, and brown algae uses fucoxanthin.
Chlorophyll absorbs all sunlight colors besides green, which is why they appear green to the human eye. The green light is what’s being reflected. Leaves slowly lose their chlorophyll during the fall months because trees shut down their photosynthesis processes because there won’t be enough sunlight to complete the process, and they need to conserve energy. As the green from chlorophyll fades away, the yellows and oranges that were in the leaves all along are then seen due to food stored in the leaves.