Photosynthesis, the starting point for energy's travels through life

Chemically speaking, respiration is photosynthesis in reverse, as you can see in this equation:

Photosynthesis: Crash Course Biology #8 - YouTube

The carbon cycle on earthis a vast interplay between the carbon dioxide of the atmosphere and itssequestration or "fixation" via photosynthesis into organic products, amongwhich cellulose is the most abundant macromolecule on earth.

photosynthesis notes - Biology Junction

During photosynthesis, chlorophyll uses energy from sunlight to make cellulose--an organic material that forms the walls in plant cells. It consists of closely spaced chains connected by hydrogen bonds.

In the oceans, however, most celluloseis produced by unicellular plankton or algae using the same type of carbondioxide fixation found in photosynthesis of land plants.