The Light-Independent Reactions of Photosynthesis (College Board AP® Biology)

The Calvin Cycle

• The light-independent stage of photosynthesis, also referred to as the Calvin cycle, occurs in the stroma of the chloroplast

• This stage produces complex organic molecules, including (but not limited to) carbohydrates, such as:

  • Starch (for storage)

  • Sucrose (for translocation around the plant)

  • Cellulose (for making cell walls)

• The light-independent stage does not require energy from light and can therefore take place in light or darkness

• However, as it requires inputs of ATP and NADPH from the light-dependent stage, it cannot continue indefinitely in darkness, as these inputs will run out

• An overview of the Calvin cycle is as follows:

  • Carbon dioxide is absorbed through the stomata of leaves into the stroma.

  • Carbon dioxide is fixed - meaning it is incorporated into organic molecules

  • NADPH and ATP are involved in converting fixed carbon into three-carbon and subsequently six-carbon sugars (e.g. glucose)

Calvin Cycle Diagram

The Calvin cycle