Oh I went through the wringer with memorizing the Krebs cycle. It's just every time you got to ATP Synthase it was literally just a tube, a few arrows, some comicbook-esque POW shapes, and "ADP" and "ATP" on both ends of the POW. Lmao.

So "oh it's a water wheel that the proton pushes that then pushes the phosphate onto the ADP" is like, "Oh. There's...a whole physical machine and not just magic 'energy transfer'". I just thought it was really cool, though obvious in retrospect.

(I am not a clever man.)