Final answer:
In photosynthesis, the energy from a photon is first used to excite electrons in chlorophyll. This energy transfer initiates the process of converting light energy to chemical energy which is then used to produce glucose.
Step-by-step explanation:
The energy of a photon in photosynthesis is first used to excite electrons in chlorophyll. When photons strike the photosystems, they transfer their energy to chlorophyll molecules. Chlorophyll, primarily chlorophyll a, absorbs this energy, resulting in the excitation of electrons. These high-energy electrons are then passed to the primary electron acceptor and eventually move through the electron transport chain. This process is crucial for powering the subsequent production of ATP and NADPH through photochemical reactions. The energy stored in ATP and NADPH is used later in the Calvin cycle to synthesize glucose.