Photosynthesis question

Question

Compare and contrast the flow of carbon in photosynthesis and cellular respiration. How are they similar and how are they different?

Answer 1

In photosynthesis, plants must undergo a process called "Carbon Fixation" to transform atmospheric carbon (in the form of carbon dioxide) into the carbon that constitutes glucose (C₆H₁₂O₆).

In cellular respiration, the carbon is already sequestered or stored as a large macromolecule such as glucose. The carbon does not undergo carbon fixation, and instead, the bonds containing the carbon atoms are broken down to release energy and ultimately the carbon is released in the form of carbon dioxide.

*The key difference here is that photosynthesis requires "Carbon Fixation" (gaseous carbon dioxide -> usable carbon for making organic molecules). Here you are going from an inorganic form to an organic form (thus its now "fixed"). But for cellular respiration, you are going from an organic form into an inorganic form (not an example of carbon fixation).

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