Final answer:
Photosynthesis consists of two stages: the light-dependent reactions, which convert sunlight into chemical energy and release oxygen, and the Calvin cycle, which uses that chemical energy to synthesize sugars from carbon dioxide.
Step-by-step explanation:
Photosynthesis occurs in two main stages: light-dependent reactions and the Calvin cycle (also known as light-independent reactions).
During the light-dependent reactions, which take place in the thylakoid membrane of the chloroplast, chlorophyll absorbs sunlight energy, which is transformed into chemical energy in the form of ATP and NADPH. Oxygen is released as a byproduct of these reactions, through the splitting of water molecules.
The Calvin cycle, taking place in the stroma of the chloroplast, uses the ATP and NADPH produced by the light-dependent reactions to fix carbon from CO2 into organic sugar molecules.
The Calvin cycle does not require light directly, but it depends on the energy carriers (ATP and NADPH) from the light-dependent reactions.
The "full" energy carriers deliver energy to the Calvin cycle, and once the energy is released, the now "empty" carriers return to the light-dependent reactions to be recharged.