At the cell level, energy from sunlight
is stored in organic molecules by photosynthesis in chloroplasts.
A byproduct of this process is oxygen.
The organic molecules and oxygen are used by mitochondria to produce ATP in a process called cellular respiration.
Byproducts of respiration are water and carbon dioxide, which are used as inputs for photosynthesis.
Heat is released into the environment in this cycle.
Exercise: