Terpena: Perbedaan revisi

2.343 bita ditambahkan ,  11 tahun yang lalu
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* '''Tetraterpena''', n=8, contohnya adalah [[likopen]], [[karoten]]
* '''Politerpena''', n besar, contohnya adalah [[karet]] dan [[getah perca]].
 
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* '''Hemiterpenes''' consist of ''a single isoprene'' unit. Isoprene itself is considered the only hemiterpene, but oxygen-containing derivatives such as [[prenol]] and [[isovaleric acid]] are hemiterpenoids.
* '''[[Monoterpenes]]''' consist of ''two isoprene'' units and have the molecular formula C<sub>10</sub>H<sub>16</sub>. Examples of monoterpenes are: [[geraniol]], [[limonene]] and [[terpineol]].
* '''[[Sesquiterpenes]]''' consist of ''three isoprene'' units and have the molecular formula C<sub>15</sub>H<sub>24</sub>. Examples of sesquiterpenes are: [[farnesene]]s, [[farnesol]]. The ''sesqui-'' prefix means one and a half.
* '''[[Diterpenes]]''' are composed for ''four isoprene'' units and have the molecular formula C<sub>20</sub>H<sub>32</sub>. They derive from [[geranylgeranyl pyrophosphate]]. Examples of diterpenes are [[cafestol]], [[kahweol]], [[cembrene]] and [[taxadiene]] (precursor of [[taxol]]). Diterpenes also form the basis for biologically important compounds such as [[retinol]], [[retinal]], and [[phytol]]. They are known to be antimicrobial and antiinflammatory.
* '''Sesterterpenes''', terpenes having 25 carbons and ''five isoprene'' units, are rare relative to the other sizes. The ''sester-'' prefix means half to three, i.e. two and a half. Examples of sesterterpenes are geranylfarnesol.
* '''[[Triterpene|Triterpenes]]''' consist of ''six isoprene'' units and have the molecular formula C<sub>30</sub>H<sub>48</sub>. The linear triterpene [[squalene]], the major constituent of [[shark liver oil]], is derived from the reductive coupling of two molecules of farnesyl pyrophosphate. Squalene is then processed biosynthetically to generate either [[lanosterol]] or [[cycloartenol]], the structural precursors to all the [[steroid]]s.
* '''Tetraterpenes''' contain ''eight isoprene'' units and have the molecular formula C<sub>40</sub>H<sub>64</sub>. Biologically important tetraterpenes include the acyclic [[lycopene]], the monocyclic [[gamma-carotene]], and the bicyclic [[alpha-carotene|alpha-]] and [[beta-carotene]]s.
* '''Polyterpenes''' consist of long chains of ''many isoprene'' units. Natural [[rubber]] consists of polyisoprene in which the double bonds are [[Geometric isomerism|cis]]. Some plants produce a polyisoprene with trans double bonds, known as [[gutta-percha]].
 
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