Amylopectin

Amylopectin /ˌæmɪlˈpɛktɪn/ is a water-soluble[1][2] polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.

Amylopectin
Amylopektin Sessel.svg
Identifiers
  • 9037-22-3 checkY
ChemSpider
  • None
ECHA InfoCard 100.029.907 Edit this at Wikidata
EC Number
  • 232-911-6
KEGG
UNII
Properties
[C6H10O5]n
Molar mass Variable
Appearance White powder
Soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Structure of the amylopectin molecule

Amylopectin bears a straight/linear chain along with a number of side chains which may be branched further. Glucose units are linked in a linear way with α(1→4) Glycosidic bonds. Branching usually occurs at intervals of 25 residues. At the places of origin of a side chain, the branching that takes place bears an α(1→6) Glycosidic bond , resulting in a soluble molecule that can be quickly degraded as it has many end points onto which enzymes can attach. Wolform and Thompson (1956) have also reported α(1→3)linkages in case of Amylopectin. Amylopectin contains a larger number of Glucose units (2000 to 200,000) as compared to Amylose containing 200 to 1000 α-Glucose units. In contrast, amylose contains very few α(1→6) bonds, or even none at all. This causes amylose to be hydrolyzed more slowly, but have higher density and be insoluble.[clarification needed]

Its counterpart in animals is glycogen, which has the same composition and structure, but with more extensive branching that occurs every eight to 12 glucose units.

Plants store starch within specialized organelles called amyloplasts. When energy is needed for cell work, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin.

Starch is made of about 70–80% amylopectin by weight, though it varies depending on the source (higher in medium-grain rice to 100% in glutinous rice, waxy potato starch, and waxy corn, and lower in long-grain rice, amylomaize, and russet potatoes, for example). Amylopectin is highly branched, being formed of 2,000 to 200,000 glucose units. Its inner chains are formed of 20–24 glucose subunits.

Dissolved amylopectin starch has a lower tendency of retrogradation (gelling) during storage and cooling. For this main reason, the waxy starches are used in different applications mainly as a thickening agent or stabilizer.

See alsoEdit

ReferencesEdit

  1. ^ "Amylose, Amylopectin (starch)". GMO Compass. Archived from the original on 2010-12-31. Retrieved 2011-02-07.
  2. ^ Green, Mark M.; Blankenhorn, Glenn; Hart, Harold (November 1975). "Which Starch Fraction is Water-Soluble, Amylose or Amylopectin?". Journal of Chemical Education. 52 (11): 729. Bibcode:1975JChEd..52..729G. doi:10.1021/ed052p729. Pure amylopectin that has not degraded is readily soluble in cold water Subscription required for online access.

External linksEdit