You sure about the "g" and the word length? It’s an eight-letter word, the fourth letter is "g"? Nothing I know quite fits the requirements. The first step in glycolysis is

ATP + glucose –> ADP + glucose-6-P

There is a way to get 1,6-GDP, but it’s not direct from one glucose and one ATP. ADP almost fits–its a diphosphate anyway, but it would be a nine-letter word and the fourth letter is "N" not "G".

Must be nine letters and the G is wrong. Adenosine?

"proteins that create ATP molecules" = ATPases

… yes!

Glucose is a carbohydrate, not a protein, so it can’t be the answer to "proteins that make ATP." Possible answers that occur to me might be "synthase" or "synthetase" or even "enzyme". ATPase could also be an answer, but unless you’re supposed to use the acronym that would be a rather long entry spelled-out. I suppose "nucleotide kinase" or "nucleoside kinase" are possibilities, though again, these are a bit longish for cross word puzzles.

you’re right, blcr. Synthase would be better (I believe the idea was to have 8 letters).

Are we/me getting answers mixed up? I don’t know how long the answer should be for the question regarding “proteins that make ATP.” Glucose can’t be the correct answer to the ATP-formation question and so I think the “g” in the supposedly eight-letter answer to the question about the diphosphate is uncertain. I’m guessing that the overlap between the two answers has it that the first letter of the “Down” clue (the ATP formation question) is the fourth letter of the “Across” clue (the diphosphate question). But now nothing I know of fits. If “synthase” is the correct answer to the ATP formation question, and “s” is now the fourth letter of the diphosphate question (and the answer is indeed eight letters) then I have no idea what it can be. “Adenosine” no longer fits and I can’t think of anything else off-hand that makes any sense. Give a cigar to the person who stumped the panel!