The substances needed for photosynthesis are water, carbon dioxide and chlorophyll. Plants require these three substances in the presence of light to convert light energy into chemical energy.
When chlorophyll molecules in plant cells absorb light, they increase the energy in some chlorophyll electrons. This allows the electrons to escape their chlorophyll molecules.
The chlorophyll molecules that lack electrons attract electrons from hydrogen atoms to take their place. These atoms are supplied by water molecules obtained from the environment, causing a chemical reaction in which water molecules break apart into oxygen atoms, protons and electrons.
Protons released from water molecules and escaped electrons from chlorophyll molecules react with one another to produce adenosine triphosphate and nicotinamide adenine dinucleotide diphosphate.