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In chemistry, a precursor is a compound that participates in a chemical reaction that produces another compound. In biochemistry , the term "precursor" often refers more specifically to a chemical compound preceding another in a metabolic pathway , such as a protein precursor .
Precursor (physics), a phenomenon of wave propagation in dispersive media; Precursor in the course of a disease, a state preceding a particular stage in that course; Precursor cell (biology), a unipotent stem cell; Earthquake precursor, a diagnostic phenomenon that can occur before an earthquake; Gehrlein Precursor, a glider
In cell biology, precursor cells—also called blast cells—are partially differentiated, or intermediate, and are sometimes referred to as progenitor cells. A precursor cell is a stem cell with the capacity to differentiate into only one cell type, meaning they are unipotent stem cells .
In biochemistry, a zymogen (/ ˈ z aɪ m ə dʒ ən,-m oʊ-/ [1] [2]), also called a proenzyme (/ ˌ p r oʊ ˈ ɛ n z aɪ m / [3] [4]), is an inactive precursor of an enzyme.A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme.
4-ANPP, also known as 4-anilino-N-phenethylpiperidine (4-ANPP), 4-aminophenyl-1-phenethylpiperidine, or despropionyl fentanyl, [3] is a direct precursor to fentanyl and acetylfentanyl. It is commonly found as a contaminant in samples of drugs containing fentanyl, which may include samples represented by the supplier as heroin or other opioids. [4]
Formaldehyde is a common precursor to more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin, melamine resin, phenol formaldehyde resin, polyoxymethylene plastics, 1,4-butanediol, and methylene diphenyl diisocyanate. [40]
Dopamine precursors including L-phenylalanine and L-tyrosine are used as dietary supplements. L-DOPA (Levodopa), another precursor, is used in the treatment of Parkinson's disease. Prodrugs of levodopa, including melevodopa, etilevodopa, foslevodopa, and XP-21279 also exist. They are inactive themselves but are converted into dopamine and hence ...
Pronounced "A-star". A graph traversal and pathfinding algorithm which is used in many fields of computer science due to its completeness, optimality, and optimal efficiency. abductive logic programming (ALP) A high-level knowledge-representation framework that can be used to solve problems declaratively based on abductive reasoning. It extends normal logic programming by allowing some ...