Photosynthesis (Light-Dependent Reactions)

In photosystem II, solar energy excites electrons and water molecules are split into hydrogen ions, oxygen molecules, and free electrons

The free electrons travel through the electron transport chain along the thylakoid membrane

As the electrons travel, some energy is used to actively transport hydrogen ions against their concentration gradient from the stroma into the inner thylakoid space

The hydrogen ions then move along their concentration gradient back into the stroma through specific channels. These channels contain enzymes that create ATP as the hydrogen atoms flow

The electrons continue on the electron transport chain (ETC) until they reach photosystem I, where electron carriers are charged

Think of photosystem I as a charging outlet

At this photosystem, chlorophyll molecules absorb photons of sunlight energy and electrons pass the energy along another electron transport chain

At the end of this chain, the electrons, NADP+, and hydrogen ions react to form NADPH, another energy carrier molecule