The Calvin Cycle Lesson for Kids

Instructor: Tamira Butler-Likely

Tamira has taught college Science and has a PhD in Biochemistry.

Like you, plants need food to grow. Plants make their food using a process called photosynthesis. In this lesson, we will learn about one part of photosynthesis: the Calvin Cycle.

What is Photosynthesis?

Photosynthesis is how plants, some algae and a few bacteria make their own food using light, water and carbon dioxide. In the process, plants release oxygen into the air for us to breathe. Photosynthesis is made up of two parts, light and dark reactions. In the light reaction, energy from the sun (light) is changed into a different energy that the plants can store. That energy is used later in the dark reactions, or the Calvin Cycle. The Calvin Cycle consists of three steps: fixation, reduction and regeneration.


Plants breathe, just like us, but instead of oxygen, they breathe carbon dioxide. Plant leaves have tiny holes called stroma that breathe in the carbon dioxide, CO2 for short. Before the CO2 can be used, it has to be fixed, or attached, to a sugar called RuBP. A protein called RuBisCo attaches the CO2 to RuBP. Once the CO2 is attached to RuBP, it changes to a new substance called 3-PGA. Now, the 3-PGA can be used in the next step of the cycle, reduction.

The first step of the Calvin cycle, fixation.
The first step of the Calvin Cycle, fixation.


During this stage, the 3-PGA from the fixation step is reduced to make a new molecule called G3P. The energy that was made in the light reactions is used to power the change from 3-PGA to G3P. That energy is in two small molecules called ATP and NADPH. There are two steps to make G3P from 3-PGA. First, 3-PGA is changed to 1,3-BPG. Next, 1,3-BPG is made into the final product, G3P. Six G3P are made in the reduction stage and are then used in the final step of the Calvin cycle, regeneration.

Reduction, the second step of the Calvin Cycle.
Step 2

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