1. Light Absorption: A chlorophyll molecule in the PSII reaction center absorbs a photon of light. This excites an electron in the chlorophyll molecule to a higher energy level.
2. Electron Transfer: The energized electron is then transferred to a series of electron carriers within PSII. These carriers include pheophytin, plastoquinone, and cytochrome b6f complex.
3. Energy Release: As the electron moves through these carriers, it loses energy. This energy is used to power the movement of protons (H+) across the thylakoid membrane, creating a proton gradient.
4. Water Splitting: The energy from light is also used to split water molecules. This process releases oxygen as a byproduct and provides electrons to replace those lost from the chlorophyll molecule.
Therefore, the energy of electrons in PSII originates from light energy, which is absorbed by chlorophyll and then used to drive electron transport and the creation of a proton gradient. This process is essential for photosynthesis, as it provides the energy needed to convert carbon dioxide into sugars.
