Answer:
Step-by-step explanation:
Photosynthetic organisms need light because this is the source of the energy that is transformed to chemical energy by chlorophyll. These organisms need water because the electrons that are excited in chlorophyll and passed to the electron transport system are replaced with electrons from a split water molecule. Hydrogen is used to form the proton gradient across the thylakoid membrane. The electrons take from the oxygen molecules in water release an oxygen gas into the atmosphere which makes living possible for us.