Editing Adenosine triphosphate (section)

====Glycolysis====
{{Main|Glycolysis}}

In glycolysis, glucose and glycerol are metabolized to [[pyruvate]]. Glycolysis generates two equivalents of ATP through [[substrate-level phosphorylation|substrate phosphorylation]] catalyzed by two enzymes,  [[phosphoglycerate kinase]] (PGK) and [[pyruvate kinase]]. Two equivalents of [[nicotinamide adenine dinucleotide]] (NADH) are also produced, which can be oxidized via the [[electron transport chain]] and result in the generation of additional ATP by [[ATP synthase]]. The pyruvate generated as an end-product of glycolysis is a substrate for the [[citric acid cycle|Krebs Cycle]].<ref name=Voet>{{cite book |last1=Voet |first1=D. |last2=Voet |first2=J.&nbsp;G. | year=2004 | title=Biochemistry |volume=1 |edition=3rd | publisher= Wiley |location=Hoboken, NJ | isbn = 978-0-471-19350-0}}</ref>

Glycolysis is viewed as consisting of two phases with five steps each. In phase 1, "the preparatory phase", glucose is converted to 2 d-glyceraldehyde-3-phosphate (g3p). One ATP is invested in Step 1, and another ATP is invested in Step 3. Steps 1 and 3 of glycolysis are referred to as "Priming Steps". In Phase 2, two equivalents of g3p are converted to two pyruvates. In Step 7, two ATP are produced. Also, in Step 10, two further equivalents of ATP are produced. In Steps 7 and 10, ATP is generated from ADP. A net of two ATPs is formed in the glycolysis cycle. The glycolysis pathway is later associated with the Citric Acid Cycle which produces additional equivalents of ATP.<ref name="glycolysis_animation">{{cite web | vauthors = Mehta S | date = 20 September 2011 | url = http://pharmaxchange.info/press/2011/09/glycolysis-animation-and-notes/ | title = Glycolysis – Animation and Notes | work = PharmaXchange | access-date = 22 September 2011 | archive-date = 25 March 2012 | archive-url = https://web.archive.org/web/20120325151810/http://pharmaxchange.info/press/2011/09/glycolysis-animation-and-notes/ | url-status = dead }}</ref>

=====Regulation=====
In glycolysis, [[hexokinase]] is directly inhibited by its product, glucose-6-phosphate, and [[pyruvate kinase]] is inhibited by ATP itself. The main control point for the glycolytic pathway is [[phosphofructokinase]] (PFK), which is allosterically inhibited by high concentrations of ATP and activated by high concentrations of AMP. The inhibition of PFK by ATP is unusual since ATP is also a substrate in the reaction catalyzed by PFK; the active form of the enzyme is a [[tetramer protein|tetramer]] that exists in two conformations, only one of which binds the second substrate fructose-6-phosphate (F6P). The protein has two [[binding site]]s for ATP&nbsp;– the [[active site]] is accessible in either protein conformation, but ATP binding to the inhibitor site stabilizes the conformation that binds F6P poorly.<ref name="Voet" /> A number of other small molecules can compensate for the ATP-induced shift in equilibrium conformation and reactivate PFK, including [[cyclic AMP]], [[ammonium]] ions, inorganic phosphate, and fructose-1,6- and -2,6-biphosphate.<ref name="Voet" /> {{confusing|date=October 2024}}