in step 6 og gycolysis where do the 2 H come from to make NADH from NAD??

Answer 1

One comes directly off from the glyceraldehyde 3-phosphate, as its replaced by another phosphate to form the 1-3 bisphosphoglycerate. The other comes off from the inorganic phosphate that's being added. Look up the structures of 1-3 glyceraldehyde and inorganic phosphate and you'll see what I mean (I can't draw them here).

Edit: Hmm, oh yeah, only one H is adding to NAD+ for each reaction. Where I got confused is that there are TWO of these reactions per molecule of glucose, so this step of glycolysis yields two NADH. So whether the H comes from the 3-glyceraldehyde, or from the inorganic phophate, is a mystery to me. My guess is its the H from glyceraldehyde, since the phosphate may or may not be unprotonated at physiological conditions.

Answer 2

...is there 2H?