Carbon Fixation

Technically, carbon fixation is defined as the first chemical reaction that incorporates carbon dioxide into an organic molecule (a molecule with more than one carbon atom).

In C3 photosynthesis the following step is considered to be carbon fixation-

carbon dioxide + RuBP ==> PGA

In CAM photosynthesis the following is considered to be carbon fixation-

carbon dioxide ===> malate

Note: CAM plants also have the reaction- carbon dioxide + RuBP ===> PGA, but in this case this step is not considered to be carbon fixation.

Sometimes people will loosely use the term carbon fixation to mean the production of glucose by photosynthesis. Be sure that you are aware of how different authors are using the term and you should attempt to use the term as precisely as possible in your own work.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- define carbon fixation
- identify carbon fixation in C3 and CAM photosynthesis