# The synthesis portion of photosynthesis is sometimes referred to as fixation; that is, the gas CO_2 is "fixed" into an organic molecule. Of the four major types of organic molecules, into which is CO_2 first fixed?

$C {O}_{2}$ taken in by the plant initially bonds to ribulose 1,5-biphosphate or $R u B P$ to form an unstable 6-carbon compound. This then divides into two three-carbon compounds of glycerate 3-phosphate. With the addition of $A T P$ and $N A D {H}_{2}$ for energy and oxidation, glycerate 3-phosphate becomes triose phosphate, which join into glucose, a sugar that is pivotal in biology.