What component is present in every part of a loop, such as one that involves proteins producing energetic molecules from sugar?

Raw materials
Energy release
Energy absorption
Information


I'm lost on the question
:eek:

How does your book use the word "loop"? I don't know what this is supposed to mean.

Is this about ATP synthesis?

My answer may not be the one you're looking for, and I'm not sure about it myself. It's just a suggestion; carbon? Or the N-H (amide) bond?