Editing Glycolysis (section)

=== Biochemical logic ===
The existence of more than one point of regulation indicates that intermediates between those points enter and leave the glycolysis pathway by other processes.  For example, in the first regulated step, [[hexokinase]] converts glucose into glucose-6-phosphate.  Instead of continuing through the glycolysis pathway, this intermediate can be converted into glucose storage molecules, such as [[glycogen]] or [[starch]].  The reverse reaction, breaking down, e.g., glycogen, produces mainly glucose-6-phosphate; very little free glucose is formed in the reaction.  The glucose-6-phosphate so produced can enter glycolysis ''after'' the first control point.

In the second regulated step (the third step of glycolysis), [[phosphofructokinase]] converts fructose-6-phosphate into fructose-1,6-bisphosphate, which then is converted into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.  The dihydroxyacetone phosphate can be removed from glycolysis by conversion into glycerol-3-phosphate, which can be used to form triglycerides.<ref>{{Cite book | vauthors = Berg JM, Tymoczko JL, Stryer L | title = Biochemistry | place = New York | publisher = Freeman | year = 2007 | edition = 6th | page = 622 | isbn = 978-0-7167-8724-2 }}</ref>  Conversely, [[triglyceride]]s can be broken down into fatty acids and glycerol; the latter, in turn, can be [[Glycerol#Metabolism|converted]] into dihydroxyacetone phosphate, which can enter glycolysis ''after'' the second control point.