Britannica Sources used in this answer

How do plants convert atmospheric carbon dioxide into carbohydrates?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — carbon group element Modern version of the periodic table of the elements (printable).

Plants convert atmospheric carbon dioxide into carbohydrates through a complex, two-stage process known as photosynthesis.12

The Light and Dark Reactions

During the initial "light" reactions, plants capture light energy to synthesize ATP and NADPH. These molecules provide the necessary energy and electrons to drive the subsequent "dark" reactions, or carbon fixation, which occur in the stroma of the chloroplast.13

The Calvin-Benson Cycle

In many species, this conversion follows the Calvin-Benson cycle, which consists of three stages:

Carboxylation: The enzyme Rubisco catalyzes the addition of carbon dioxide to ribulose 1,5-bisphosphate, eventually producing molecules of PGA.4
Reduction: Using the ATP and NADPH generated earlier, the plant reduces these compounds to form glyceraldehyde-3-phosphate (Gal3P).3
Regeneration: The cycle regenerates the starting compounds to continue the process.3

The resulting three-carbon sugars are either exported or converted into starch and sucrose for energy storage and structural use.312