When a photon is absorbed by a pigment molecule, what typically happens next?

• A. The pigment becomes excited and energy is transferred
• B. The pigment dissolves
• C. The pigment emits a second photon
• D. The pigment loses all energy and returns to ground state instantly

Answer: (A)

When a photon is absorbed, the pigment’s electron is promoted to a higher energy level, putting the pigment in an excited state. In light-harvesting systems, that excitation is then rapidly passed to neighboring pigments through resonance energy transfer, guiding the energy toward the reaction center. This non-radiative transfer is fast and efficient, and it sets up the reaction center to drive charge separation and begin the electron transport chain. While an excited pigment can sometimes relax by emitting light (fluorescence) or releasing energy as heat, those are not the typical next steps in the energy transfer process; the common pathway is excitation followed by energy transfer to the reaction center.