**3.2 Reduction**

The reduction stage involves the conversion of 3-phosphoglycerate (3-PGA) into glyceraldehyde-3-phosphate (G3P) through two enzyme-catalyzed reactions [26, 27]. First, 3-PGA is phosphorylated by the enzyme phosphoglycerate kinase (PGK), yielding 1,3-bisphosphoglycerate (1,3-BPG) [28]. This reaction requires ATP as a substrate, which is converted into ADP during the process. This step highlights the importance of phosphorus, as ATP is the primary energy currency of the cell and contains a highenergy phosphate bond. Next, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the reduction of 1,3-BPG to G3P, using NADPH as a reducing agent [29]. NADPH, which is another essential molecule containing phosphorus, is generated during the light-dependent reactions of photosynthesis.
