# Phosphorylation --- **Phosphorylation** is a [[chemical reaction]] in which a [[functional group#Biologically Important Functional Groups|phosphate]] group is added to a molecule. Phosphorylation happens a lot in biochemistry as the energy that it can store is easy to build up and harness, particularly in the form of [[adenosine triphosphate]]. The phosphorylation of a [[protein]] will often dramatically affect the protein's activity. ## Types Phosphorylation can occur in multiple different ways, most notably by *substrate-level phosphorylation* and *oxidative phosphorylation* substrate-level phosphorylation | oxidative phosphorylation --------------------------------|----------------------------- • *direct* formation of [[adenosine triphosphate]] by transfering a phosphate to an [[adenosine triphosphate|ADP]]<br>•occurs in [[glycolysis]] and the [[citric acid cycle]]|•*indirect* formation of [[adenosine triphosphate]] from oxidizing [[NAD\|NADH]] and [[FAD\|FADH2]] in the [[ETC (mitochondria)\|ETC]]<br>•occurs in the [[ETC (mitochondria)\|ETC]] ## Substrate-Level Phosphorylation **Substrate-level phosphorylation** is a metabolic reaction where [[adenosine triphosphate]] or [[GTP]] is created *directly* by combining an inorganic phosphate an [[adenosine triphosphate|ADP]] or [[GTP|GDP]] with the help of a specific [[enzyme]]. The inorganic phosphate can be free floating, or attached to a different substance, like a sugar. ![[substrate-level phosphorylation.png]] ### Not To Be Confused With "Substrate-level phosphorylation" is not to be confused with "substrate phosphorylation", where a substrate is phosphorylated by *using* ATP. (Which is, basically, the exact opposite.) ## Oxidative Phosphorylation **Oxidative phosphorylation** is the process of *indirectly* generating [[adenosine triphosphate]] by harnessing [[osmosis#Chemiosmosis|chemiosmosis]] of hydrogen ions to power an enzyme complex called [[ATP synthase]]. Oxidative phosphorylation takes place in the [[ETC (mitochondria)|ETC]] #### On The Importance of Oxygen Oxygen is absolutely vital oxidative phosphorylation, but not because of the "oxidative" part—that's a [[redox#Oxidation|different thing]]. Oxygen is needed in order to accept the electron that has been bopped down the chain, fueling the proton pump. ## Other Types [[ETC (chloroplast)|photophosphorylation]] [[enzyme-linked receptors|phosphorylation cascade]] ___