Photosynthesis: Cyclic Electron Flow

In some cases, the electrons may take an alternate cyclic pathway in which pigments capture energy from the sun in photosystem 1.

As per usual, the energy is transferred to the alpha glucose in the reaction centre and an electron is transferred to the primary electron acceptor.

From there, ferredoxin carries it to the b6-f complex and plastocyanin carries it back to photosystem 1 where it may replace another lost electron.

In the process, a proton gradient is created for ATP synthesis.

This type of electron flow DOES NOT allow for carbon fixation because there are no electrons released to form NADPH, a energy carrier necessary for the reduction of carbon dioxide.