Operational definition
Energy-conversion mechanism.
The conversion of photon energy into a biologically conserved form through excitation of a photoactive molecule.
The immediate conserved result may be:
- charge separation;
- a stronger reductant or oxidant;
- electron flow;
- proton or sodium translocation;
- an electrochemical gradient.
Photochemical conversion is the first conversion step of phototrophy. It precedes ATP production or carbon fixation.
21.1 Molecular excitation
hν → excited pigment
21.2 Charge separation
excited reaction center → separated electron and hole
21.3 Light-driven ion pumping
hν → Δ μ_ion