Dark Reaction

These reactions occur without light but can occur with light as well. This stage of photosynthesis is also known as the Calvin Cycle or the dark reactions.


The Carbon-fixation reaction occurs at this stage. This reaction uses the energy (in the form of ATP) produced from the light stage to provide the energy needed to combine the hydrogen (also produced from the light stage) with carbon dioxide to form glucose (C6H12O6). Several enzymes are used in the process of converting CO2 to carbohydrates. The overall process is represented by the equation below:

Word equation for overall reaction:

Chemical equation for overall equation:


-Carbon dioxide is obtained from the air by the leaves of the plant via diffusion.

-Water is obtained by the leaf cells from the plant’s transport systems.

-Sunlight is absorbed by the chlorophyll in the leaves and supplies the light energy needed for the process.

-Carbohydrates that are produced is mainly glucose and is transported throughout the plant and later produces starch. Oxygen is merely a by-product.

Previous | Next