CHEM 407 - Glycolysis - 6 - Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH)

Glycolysis begins to yield net gains in energy at the GAPDH step, where NADH is generated from the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate.

[@kalkidanberhanu7708]

Thanks for the video! This really clears things up :)

[@houranimowlabucus2885]

The equation for this reaction is often written as : GAP + Pi + NAD+ ----> 1,3 BPG + NADH + H+. Can you please explain where does this H+ come from? Is it the H+ from cysteine?

[@BiochemistrywithDrMauser]

Hi! Any time a reduction happens using a dehydrogenase, an entire equivalent of Hydrogen (H2) is removed. The NAD+ removes an H with its pair of electrons (H:-), while one H+ is lost as an acidic proton. In this case, the aldehyde hydrogen is lost as the H:- and the H+ is lost from the phosphate group. While it's written as Pi, remember that phosphate largely exists as HPO4 (2-) at physiological pH. When attached to the molecule, it ends up as an OPO3 (2-), losing its H+.
Hope that helps!

[@ainbrisk545]

Thanks for the explanation! I was just wondering, if the end result is an OPO3 (2-) attached to the carbon at the end, why is it drawn with the hydrogen still bonded in the video? Am I misunderstanding something?

[@bambleskrt7382]

@@BiochemistrywithDrMauser Know this is late but thank you! I have been struggling with this since last year and I just needed that simple explanation!

[@mahinuddin5985]

This video is amazing!!!!

[@satellitesage2487]

This step is converting glyceraldehyde 3 phosphate to 1, 3-bisphosphoglycerate which has a chemical formula of C3H7O6P and C3H8O10P2 respectively. G3p gives one of its hydrogen to NAD+.I don't understand where did 1, 3-bisphosphoglycerate got its 2 hydrogen and 4 oxygen. I also don't have any background with thioesters.

[@BiochemistrywithDrMauser]

1,3 - BPG has the molecular formula C3H8O10P2 when fully protonated. G3P gains a phosphorus, 2 hydrogens, and 4 oxygens from the addition of the phosphate group (H2PO4(-) to the thioester and resolution of the tetrahedral intermediate. The one H:- which previously was at the aldehyde group is passed to NAD+.

[@satellitesage2487]

Ohh. Thank youu so muuch! :)

[@ashnaabdulqadr5432]

how many glyceraldehyde carbon numbers??

[@ashnaabdulqadr5432]

please