The role of CO2

• Carbon dioixde is the source of carbon for the production of all organic molecules found in carbon based life form on earth.
• The organic molecules that form all carbon-based life forms may be used as structures, like cell membranes, antigens, enzymes muscle proteins and cellulose cell walls.
• Carbon dioxide in air enters a leaf through its stomata and diffuses through the spongy mesophyll layer into the palisade layer into the palisade cells through their thin cellulose cell walls and then the chloroplast envelope into the stroma.
• The fixation of carbon dioxide in the stroma maintains a concentration gradient that aids the diffusion of carbon dioxide.
• Carbon dioxide is a by product of respiratioon in plant cells, so it can also be used for this stage of photosynthesis.