Glyceraldehyde-3-phosphate dehydrogenase catalyzes the phosphorylation of glyceraldehyde-3-phosphate, but unlike other glycolytic reactions, it does not require energy investment from atp. this reaction occurs in two stages: oxidation/reduction and phosphorylation. why is the oxidation/reduction reaction necessary to make phosphorylation favorable

Oxidation/reduction reaction is necessary in this stage in order to provide ATP necessary for phosphorylation

Explanation:

A brief explanation of Glycolysis is that it comprises of two stages.

Stage 1 involves trapping and preparation phase. No ATP is generated in this stage.

stage 2 ATP are generated and converted to pyruvate.

Oxidation/Reduction or  "redox"  refers to the transfer of electrons that occurs during many chemical reactions. Electron transfer is important to the life of a cell and for phosphorylation in this case. During cellular respiration, there is a relocation of electrons. This relocation results in the release of energy that is stored in food molecules, and the released energy is used to synthesize ATP.

According to first law of thermodynamics which describes the conversion of energy; you can't "make" energy but energy can be transferred from one molecule to another.

Hope this helps.