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Is the production of ATP in photosynthesis similar to the production of ATP in cellular respiration? Photosynthesis is often described as the reverse of cellular respiration. Respiration breaks down complex molecules to release energy that is used to make ATP. Photosynthesis takes energy from photons and uses it to build complex molecules. However both systems use an electron transport chain and associated proton pump and ATP synthase as a key part of the process. In photosynthesis electrons enter the transport chain after receiving light energy – in respiration the electrons are provided by organic food molecules. In both cases the electron transport chain uses the energy to pump hydrogen ions across a membrane. The protons pass back through ATP synthase, driving the production of ATP. In photosynthesis this ATP is used to construct organic molecules from carbon dioxide and water.