IB Biology Sub-topic C1.3 Notes

Whilst respiration uses oxygen and organic compounds to produce energy, photosynthesis does nearly the opposite. It is the production of organic compounds and oxygen from light, CO₂, and water. This reaction is only conducted in certain types of organisms - namely plants, algae, and cyanobacteria. The specific reaction they undergo is:

CO₂ + H₂O → glucose + O₂

A summary of the process is:

1. First, light energy is absorbed by photosynthetic pigments called chlorophyll.
2. This energy is used to split water molecules in a process called photolysis, producing electrons and oxygen as waste.
3. Finally, the electrons are used to convert CO₂ into organic compounds (glucose).

HL students need to learn a more detailed process.