Difference between Substrate level phosphorylation, Oxidative phosphorylation and Photophosphorylation

 Phosphorylation can be defined as a biochemical process in which a phosphate molecule is added to some organic compound, such as glucose and adenosine diphosphate (ADP).

Inside the cell, the most common type of phosphorylation is the formation of ATP by the addition of phosphate group to ADP.

There are 3 Types of Phosphorylation occurring in a cell

Substrate level phosphorylation

A metabolism reaction that results in the production of ATP or GTP by the transfer of a phosphate group from a substrate directly to ADP or GDP.

Oxidative phosphorylation during cellular respiration

Oxidative phosphorylation (OXPHOS) is defined as an electron transport chain driven phosphorylation by substrate oxidation coupled ATP synthesis through an electrochemical transmembrane gradient.

Photo phosphorylation in Photosynthesis

The phosphorylation of ADP to form ATP using the energy of sunlight during photosynthesis is called photophosphorylation.

Let’s have a comparison of these 3 types.

	Substrate level Phosphorylation	Oxidative Phosphorylation	Photophosphorylation
Source of Phosphate	Organic molecule	Inorganic phosphate PO43-	Inorganic phosphate
Energy Source	High energy phosphate bond of donor	Proton motive force	Proton motive force
Location in Eukaryotes	Cytosol and mitochondrial matrix	Inner membrane of mitochondrion	Thylakoid of chloroplast
Location in Prokaryotes	Cytosol	Cytoplasmic membrane	Thylakoid on chromatophores
Oxygen?	Oxygen not involved.	Oxygen as terminal electron acceptor	Oxygen evolved by photolysis of water.
Metabolic pathway	Common in many metabolic pathways like glycolysis, TCA cycle etc	Cellular respiration	Photosynthesis
Pigments?	Not involved	Not involved	Involved as two photosystems PSI and PSII