English:
1. Energy in the form of sunlight
2. The light dependent reactions take place when the light excites a reaction center, which donates an electron to another molecule and starts the electron transport chain to produce ATP and NADPH.
3. Once NADPH has been produced, the Kreb’s cycle proceeds as in oxygenic photosynthesis, turning CO2 into glucose.

Micro-essay: While most photosynthesis is done in the presence of water and releases oxygen, there are several types of anoxygenic photosynthesis that use another substance as a reducing agent [1]. Green sulfur bacteria (GSB) use H2S instead of water to donate electrons [2]. Light energy stimulates the electron transport chain, which is composed of one photosystem (similar to Photosystem I) that acts cyclically [2]. As the electron goes through the cycle, it generates ATP by oxidative phosphorylation and reduces NADP+ to NADPH [1]. This NADPH is used in the Krebs cycle, which proceeds as in ordinary photosynthesis to turn CO2 into glucose.

1.Hanada, S. (2016, March). Anoxygenic Photosynthesis —A Photochemical Reaction That Does Not Contribute to Oxygen Reproduction—. Retrieved May 18, 2017, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4791109/

2.Anoxygenic Photosynthesis. (n.d.). Retrieved May 21, 2017, from https://courses.cit.cornell.edu/biomi290/z.OldWebSite/ANOXY.HTML