Calvin Cycle

What is it?

The process plants go through to turn the carbon dioxide (CO2) they receive into the sugars they need to survive.

Every living thing depends on the Calvin Cycle

  • Plants - for food and energy

  • Herbivores - indirectly because they eat plants for food

  • Carnivores - for energy, food and nutrients through the herbivores it eats

Discovered by Dr. Melvin Calvin in 1957

Three Main Stages:

  1. Fixation

  • The fixation of carbon dioxide

  • Begins with 3CO2

  • The enzyme Rubisco helps catalyze the reaction with Ribulose 1,5 bisphosphate (RuBP)

  • This forms an unstable compound

  • Which ends up being 6 molecules of 3-phosphoglycerate (PGA)

  • The technical equation is as follows:

    • 3 atoms from 3CO2 + 15 atoms from 3RuBP = 18 atoms in 3 atoms of 3-PGA

  1. Reduction

      • The reduction of 3-phosphoglycerate to G3P

      • The 6 3-PGA receives 1 ATP and 1 NADPH

      • This reaction changes it to 6 glyceraldehyde-3-phosphate (G3P)

      • A G3P is half of a glucose

  2. Regeneration

      • The regeneration of RuBP from G3P

      • One G3P leaves the cycle to be used for food, energy or storage

      • The remaining 5 G3P are rearranged again with ATP to regenerate the RuBP

      • This starts the cycle all over again

A bit more information:

Each turn of the cycle produces 1 G3P so the cycle has to run 6 times before a 6C carbohydrate molecule can be made

The sugars made are used for glucose (food), starch (energy), and cellulose (structure)

The Calvin Cycle does not require sunlight energy to work

By: Jaime Blokker 2021