During plant
photosynthesis, 2 equivalents of
glycerate 3-phosphate (GP; also known as 3-phosphoglycerate) are produced by the first step of the
light-independent reactions when
ribulose 1,5-bisphosphate (RuBP) and
carbon dioxide are catalysed by the
rubisco enzyme. The GP is converted to D-glyceraldehyde 3-phosphate (G3P) using the energy in
ATP and the reducing power of
NADPH as part of the
Calvin cycle. This returns
ADP, phosphate ions Pi, and
NADP+ to the
light-dependent reactions of photosynthesis for their continued function. RuBP is regenerated for the Calvin cycle to continue. G3P is generally considered the prime end-product of photosynthesis and it can be used as an immediate food nutrient, combined and rearranged to form monosaccharide sugars, such as
glucose, which can be transported to other cells, or packaged for storage as insoluble
polysaccharides such as
starch.
Balance sheet 6 CO2 + 6
RuBP (+ energy from 12
ATP and 12 NADPH) →12
G3P (3-carbon) 10
G3P (+ energy from 6
ATP) → 6
RuBP (i.e. starting material regenerated) 2
G3P →
glucose (6-carbon). ==In tryptophan biosynthesis==