Cyclic Photophosphorylation: Electrons loop back after completing photosystem 1, creating a cycle where electrons don't leave from. However, only ATP is created. OR Noncyclc photophosphorylation can occur. Either was, anoxygenic photosynthesis produces only ATP or NADPH (they cannot be produced simultaneously.)

Pathway of Anoxygenic Photosynthesis

Photosynthesis that does not use water as the terminal electron donor. Instead, they use reduced inorganic electron donors such as hydrogen sulfide, ferrous ions, etc. Due to not involving water, no oxygen is produced as a result.

University of California, Davis

Photosynthesis is the process of using the sun's light as energy and converting it to chemical energy to fix gaseous carbon dioxide and create sugars such as glucose. The first organisms with the capability to photosynthesize stemmed from prokaryotes 3.8 billion years ago. What is required for photosynthesis include a light source, carbon, electron donor, and pigments to harvest energy.

Photosynthesis

Life: The Science of Biology(12th edition)

Emerged when cyanobacteria (a type of prokaryote) used water as their terminal electron donor, releasing oxygen as a byproduct. 

Oxygenic Photosynthesis

Anoxygenic Photosynthesis

A biological kingdom within the Eukarya domain whose members, commonly known as plants, are typically characterized by having cell walls containing cellulose and the ability to produce their own nutrients through photosynthesis.

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