The photosystems found in the thylakoid membrane of the plants are the structural and functional unit of photosynthesis. Purple bacteria has a single photosystem with bacteriochlorophyl. They do not produce oxygen while doing photosynthesis. ATP production occurs via cyclic photophosphorylation. Their electron donor is elemental sulfur. Green Bacteria- undergo anoxigenic phototrophy. They also possess a single photosystem with bacteriochlorophyl.. ATP is produced by cyclic photophosphorylation. Electron donor is thiosulfare or H2S. Alters the ATP or NADH. Cyanobacteria- Has 2 different photosystems and reaction centres. They undergo oxygenic phototrophy. They fix CO2, and generate ATP and reducing power in a single process. They have a similar process of photosynthesis as plants. The electrons passes through the electron transpot chain fro photosystem I to photosystemII. And ultimately NADPH+ prodeces from NADP+. Solution The photosystems found in the thylakoid membrane of the plants are the structural and functional unit of photosynthesis. Purple bacteria has a single photosystem with bacteriochlorophyl. They do not produce oxygen while doing photosynthesis. ATP production occurs via cyclic photophosphorylation. Their electron donor is elemental sulfur. Green Bacteria- undergo anoxigenic phototrophy. They also possess a single photosystem with bacteriochlorophyl.. ATP is produced by cyclic photophosphorylation. Electron donor is thiosulfare or H2S. Alters the ATP or NADH. Cyanobacteria- Has 2 different photosystems and reaction centres. They undergo oxygenic phototrophy. They fix CO2, and generate ATP and reducing power in a single process. They have a similar process of photosynthesis as plants. The electrons passes through the electron transpot chain fro photosystem I to photosystemII. And ultimately NADPH+ prodeces from NADP+..