5/31/2023 0 Comments Coursenotes ap bio chapter 8![]() 8.3 Using Light to Make Organic Molecules ![]() Photosystem I absorbs a second photon, which results in the formation of an NADPH molecule, another energy and reducing power carrier for the light-independent reactions. The ions flow through ATP synthase via chemiosmosis to form molecules of ATP, which are used for the formation of sugar molecules in the second stage of photosynthesis. This action builds up a high concentration of ions. The energy travels to the reaction center that contains chlorophyll a and then to the electron transport chain, which pumps hydrogen ions into the thylakoid interior. A photon strikes the antenna pigments of photosystem II to initiate photosynthesis. The pigments of the first part of photosynthesis, the light-dependent reactions, absorb energy from sunlight. 8.2 The Light-Dependent Reaction of Photosynthesis In prokaryotes, such as cyanobacteria, the process is less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates. Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere. Only certain organisms, called photoautotrophs, can perform photosynthesis they require the presence of chlorophyll, a specialized pigment that absorbs certain portions of the visible spectrum and can capture energy from sunlight. Because of photosynthesis, living things gained access to sufficient energy that allowed them to build new structures and achieve the biodiversity evident today. By harnessing energy from the sun, the evolution of photosynthesis allowed living things access to enormous amounts of energy. The process of photosynthesis transformed life on Earth.
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