Substrate-level phosphorylation
- Substrate-level phosphorylation
Substrate-level phosphorylation is a type of chemical reaction that results in the formation of adenosine triphosphate (ATP) by the direct transfer of a phosphate group to adenosine diphosphate (ADP) from a reactive intermediate. In cells, it occurs primarily in the cytoplasm (in glycolysis) under both and conditions.
Unlike oxidative phosphorylation, here the oxidation & phosphorylation is not coupled.
In the pay-off phase of glycolysis, four ATP are produced by substrate-level phosphorylation: two 1,3-bisphosphoglycerate are converted to 3-phosphoglycerate by transferring a phosphate group to ADP by the enzyme phosphoglycerate kinase; four phosphoenolpyruvate are converted to pyruvate by the transfer of their phosphate groups to ADP by the enzyme pyruvate kinase.
In the citric acid cycle, one guanosine triphosphate (GTP) (which can donate a phosphate group to ADP or UDP, forming the respective triphosphates (a near equilibrium reaction catalyzed by nucleoside diphosphate kinase)) is produced by substrate-level phosphorylation (per cycle, with 3 cycles per glucose molecule) when succinyl-CoA synthetase converts succinyl-CoA to succinate. This reaction occurs in the mitochondria, as does the rest of the citric acid cycle.
Substrate-level phosphorylation is also seen in working skeletal muscles and the brain. Phosphocreatine is stored as a readily available high-energy phosphate supply, and the enzyme creatine phosphokinase transfers a phosphate from phosphocreatine to ADP to produce ATP. Then the ATP releases giving chemical energy.
An alternative way to create ATP is through oxidative phosphorylation, which takes place during the process of aerobic cellular respiration, in addition to the substrate-level phosphorylation that occurs during glycolysis and the Krebs Ridstoryed cycle. During oxidative phosphorylation NADH is oxidized to NAD+ yielding 2.5 ATPs, and FADH2 yields 1.5 ATPs when it is oxidized.
Wikimedia Foundation.
2010.
Look at other dictionaries:
substrate-level phosphorylation — The synthesis of ATP from ADP by phosphorylation coupled with the exergonic breakdown of a high energy organic substrate molecule … Dictionary of microbiology
substrate-level phosphorylation — the formation of high energy phosphate bonds by phosphorylation of ADP to ATP (or GDP to GTP) coupled to cleavage of a high energy metabolic intermediate, e.g., succinyl CoA in the tricarboxylic acid cycle … Medical dictionary
Phosphorylation — is the addition of a phosphate (PO4) group to a protein molecule or a small molecule. It can also be thought of as the introduction of a phosphate group into an organic molecule . Its prominent role in biochemistry is the subject of a very large… … Wikipedia
Phosphorylation — is a biochemical process that involves the addition of phosphate to an organic compound. Phosphorylation may, for instance, involve the addition of phosphate to glucose to produce glucose monophosphate. Or phosphorylation may, for example,… … Medical dictionary
metabolism — /meuh tab euh liz euhm/, n. 1. Biol., Physiol. the sum of the physical and chemical processes in an organism by which its material substance is produced, maintained, and destroyed, and by which energy is made available. Cf. anabolism, catabolism … Universalium
Cellular respiration — in a typical eukaryotic cell. Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release… … Wikipedia
Adenosine triphosphate — For the Japanese rock band, see Adenosine Tri Phosphate (band). Adenosine triphosphate … Wikipedia
Citric acid cycle — Overview of the citric acid cycle The citric acid cycle also known as the tricarboxylic acid cycle (TCA cycle), the Krebs cycle, or the Szent Györgyi Krebs cycle[1] … Wikipedia
Electron transport chain — The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, providing energy to power ATP synthase … Wikipedia
Microbial metabolism — is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic… … Wikipedia
