Final answer:
The excited PSII reaction-center pigment (P680*) transfers a photoexcited electron to pheophytin. Pheophytin acts as the primary electron acceptor in the photosynthetic electron transport chain within photosystem II, facilitating the subsequent production of ATP and NADPH for the Calvin cycle.
Step-by-step explanation:
The excited PSII reaction-center pigment (P680*) transfers a single photoexcited electron to a closely associated, chlorophyll-like molecule called pheophytin. This molecule is crucial in the initial steps of the photosynthetic electron transport chain within photosystem II (PSII). Once excited by photons, the energy from the light is passed through pigments to chlorophyll a molecules which then excite electrons. These electrons are transferred to pheophytin, which acts as the primary electron acceptor. Subsequently, the electrons enter an electron transport chain, leading to the production of vital molecules like ATP and NADPH, which are later used in the Calvin cycle to produce glucose.