The three-carbon sugar produced when PGA (phosphoglycerate) combines with hydrogen from NADPH is glyceraldehyde 3-phosphate (G3P).

This reaction is a key step in the Calvin cycle, the light-independent reactions of photosynthesis.

Here's a breakdown:

* PGA (phosphoglycerate): A three-carbon molecule formed during the initial stages of the Calvin cycle.

* NADPH: A reduced form of nicotinamide adenine dinucleotide phosphate that carries high-energy electrons and acts as a reducing agent.

* Hydrogen from NADPH: The electrons from NADPH are used to reduce PGA, adding a hydrogen atom.

* G3P (glyceraldehyde 3-phosphate): A three-carbon sugar that is a key intermediate in both photosynthesis and glycolysis.

The overall reaction:

PGA + NADPH + H⁺ → G3P + NADP⁺ + H₂O