Calvin Cycle Diagram Labeled

The light-independent reactions as one circle of three stages: 14 parts to name.

Calvin Cycle Diagram Labeled

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13 14
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Write the name of each numbered part.Answer key

  1. Stroma
  2. Stage 1: Fixation
  3. Stage 2: Reduction
  4. Stage 3: Regeneration
  5. Carbon dioxide (CO2)
  6. RuBisCO
  7. RuBP (ribulose bisphosphate)
  8. 3-PGA (3-phosphoglyceric acid)
  9. G3P (glyceraldehyde 3-phosphate)
  10. ATP
  11. NADPH
  12. ADP
  13. NADP+
  14. G3P leaving the cycle

Drawn for this site by script, 2026-09-26. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: ATP, the energy the cycle spends

All 14 parts on the diagram

Show the list

Start here: 8 main parts 8

  1. Stroma The fluid inside the chloroplast, around the thylakoids. It is the site of the light-independent reactions.
  2. Stage 1: Fixation RuBisCO joins CO2 to RuBP. This makes two molecules of 3-PGA for each CO2. Carbon is fixed from an inorganic form into organic molecules.
  3. Stage 2: Reduction ATP and NADPH turn 3-PGA into G3P. It is a reduction because 3-PGA gains electrons.
  4. Stage 3: Regeneration Five of every six G3P molecules are rearranged to rebuild RuBP. This uses more ATP. The cycle can then fix more CO2.
  5. Carbon dioxide (CO2) Enters the leaf through the stomata. It diffuses into the stroma, where it is fixed. Only one CO2 is fixed per turn.
  6. RuBisCO Ribulose-1,5-bisphosphate carboxylase/oxygenase: the enzyme that joins CO2 to RuBP.
  7. RuBP (ribulose bisphosphate) The five-carbon molecule that starts the cycle. It is flanked by two phosphates and rebuilt at the cycle's end.
  8. G3P (glyceraldehyde 3-phosphate) The three-carbon sugar made by reduction. Most of it stays in the cycle to rebuild RuBP.

Stages, output and stroma: 5 1

  1. G3P leaving the cycle For every three turns, one G3P leaves for the cytoplasm. It goes to build other compounds. Six turns yield one six-carbon glucose.

Carbon molecules and RuBisCO: 5 1

  1. 3-PGA (3-phosphoglyceric acid) Made by fixation: two for every CO2 fixed. Each has three carbons and one phosphate.

Energy carriers: 4 4

  1. ATP Brings energy from the light reactions. Reduction uses six ATP per three turns, and regeneration three more.
  2. NADPH Brings energy and the electrons, as hydrogen, that reduce 3-PGA to G3P.
  3. ADP ATP after losing its end phosphate. It returns to the light reactions to be recharged.
  4. NADP+ NADPH after giving up energy and a hydrogen. It returns to the light reactions to be recharged.

How this list was compiled: Read 2026-09-26. OpenStax Biology 2e, section 8.3 Using Light Energy to Make Organic Molecules, https://openstax.org/books/biology-2e/pages/8-3-using-light-energy-to-make-organic-molecules : CO2 entering through stomata and diffusing into the stroma, the site of the light-independent reactions; the names Calvin cycle and Calvin-Benson cycle and the outdated dark reaction; the three stages fixation, reduction and regeneration; RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) and RuBP, five carbons flanked by two phosphates; two 3-PGA of three carbons and one phosphate for each CO2; one CO2 per turn, three turns for one G3P and six for one glucose; six ATP and six NADPH used in reduction, becoming ADP and NADP+ that return to the light reactions; one of six G3P leaving for the cytoplasm and five regenerating RuBP with three more ATP. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

A Calvin cycle diagram labeled with 14 parts: the three stages as arrows round one circle in the stroma, the carbon molecules drawn as chains of beads, and the energy carriers going in and out. Start with the 8 main parts.

Read the full guide

Reading the beads

Small beads are carbons and large beads are phosphates. RuBP has five carbons between two phosphates; 3-PGA and G3P each have three carbons and one phosphate, and you tell them apart by where they sit.

Three turns, one G3P

Each turn fixes one CO2, so three turns make six G3P. One leaves the cycle to build sugars and other compounds, and five rebuild the three RuBP. Six turns give enough for one glucose.

  • Stage order spells the story: fix the carbon, reduce it with ATP and NADPH, then regenerate RuBP.

Questions and answers

Where does the Calvin cycle take place?

In the stroma of the chloroplast, the fluid around the thylakoids. It is also called the light-independent reactions or the Calvin-Benson cycle.

What does RuBisCO do?

It is the enzyme that joins CO2 to RuBP in the fixation stage, making two molecules of 3-PGA for each CO2.

Why is it wrong to call it the dark reaction?

The name suggests it happens only at night. It does not need light directly, but it runs on the ATP and NADPH the light reactions make.

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