AP BIOLOGY

Detailed explanation-1: -Chlorophyll is therefore said to “donate” an electron (Figure 5.12). To replace the electron in the chlorophyll, a molecule of water is split. This splitting releases an electron and results in the formation of oxygen (O2) and hydrogen ions (H+) in the thylakoid space.

Detailed explanation-2: -Light that is harvested from PSII causes an excited electron of the chlorophyll a special pair to be passed down an electron transport chain (Pq, Cyt, and Pc) to PSI. The electron lost from the chlorophyll a special pair is replenished by splitting water.

Detailed explanation-3: -In the electron transport chain, electrons are passed from one molecule to another, and energy released in these electron transfers is used to form an electrochemical gradient. In chemiosmosis, the energy stored in the gradient is used to make ATP.

Detailed explanation-4: -The electrons then exit the photosystem and move down the electron transport chain. As electrons move from one component to the next, they release energy. The electrons that have left photosystem II need to be replaced, and these electrons are provided by the photolysis of water.