The light-independent reaction in such detail as to show that • carbon dioxide is accepted by ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP) • ATP and reduced NADP are required for the reduction of GP to triose phosphate • RuBP is regenerated in the Calvin cycle • Triose phosphate is converted to useful organic substances.

In the stroma of a chloroplast the light-independent stage of photosynthesis happens. It involves taking up carbon to make glucose using the products from the light-dependent stage.

The molecule RuBP (ribulose biphosphate) is made up of five carbons, a molecule of carbon from CO2 is added to make a six carbon compound. This is very unstable and quickly breaks down into two bits of GP (glycerate 3-phosphate) each with three carbons.

GP is then reduced by NADPH, which gives over its H to become NADP, and restructured by ATP, giving energy as it breaks bonds. The molecule made from this is triose phosphate and because there were two GP we have two triose phosphate molecules too.

One carbon is removed, and this carbon is used to make glucose. There are 6 carbons in a glucose so it is made every sixth time the process is repeated.

The remaining five carbons (two from one molecule of triose phosphate and three from the other) are the rearranged using the energy from ATP to create RuBP (the origional 5 carbon molecule).

This is known as the Calvin cycle.