Light Reaction

Light Dependent Reaction

Step1

Photon strikes PSII and excites an electron

The excited electron left PSII and go to electron carrier (Redox Reaction, PSII oxidized)

H2O splited by Water-Spliting Enzyme, sends one electron

Oxygen and Hydrogen ion is then produced. Oxygen goes outside of the cell as a by-product, and the Hydrogen ion remains in Thylakoid space

Step2

Electrons from PSII is transfered through a series of REDOX reactions (ElectronTransportSystem)

As pass through those proteins, Energy is released to pump Hydrogen ions into the Thylakoid space

This finally creates a Ion-Gradient. The concentration of Hydrogen ions is higher inside and can be used for chemiosmosis

Step3

PhotoSystemI captures light Energy and excites electron

The excited electron leaves PhotoSystemI and then replenished by the electron from PhotoSystem II

Step4

NADP Reductase needs to be oxidized

So NADP+, the final electron acceptor, pulls electron out of the chain and produces NADPH

Chemiosmosis & ATP

ATP Synthase pumps H+ out of the membrane to make ATP

The left H+ ion is then combined with NADP+ to form NADPH in the stroma.

Electron Transport Cyclic Flow:

Occurs at PhotoSystem I

The electron carrier didn't take the excited electron to NADP reductase, but take it back to b6-f complex.

So no NADPH is made at this round because the electron is not delivered to NADP reductase. However this won't affect ATP syntheize and one more ATP is made.

Because a ratio of 3ATP:2NADPH is needed for Calvin Cycle to continue, so one more ATP must be made.

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