Amylopectin: Structure & Function

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  • 0:02 Amylopectin
  • 1:55 Structure of Amylopectin
  • 3:35 Amylopectin's Function
  • 4:24 Lesson Summary
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Lesson Transcript
Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

A type of starch with a unique structure, amylopectin is one fascinating molecule. Read this lesson to explore the structure and function of amylopectin. Don't forget to test your knowledge at the end of the lesson by taking a short quiz.

Amylopectin: Introduction and Background

Did you know russet potatoes, which you can use to make an awesome batch of French fries, contain a molecule called amylopectin? Not just russet potatoes, but other starchy products like rice, wheat, and corn all contain this molecule. This begs the question, what is amylopectin?

Amylopectin is a type of polysaccharide that has a variable structure built from multiple glucose units. As a quick review, a polysaccharide is a molecule that has more than one sugar unit (ie. glucose). Amylopectin is one half of the structure of starch. Starch is a type of carbohydrate that contains two different polysaccharides. If amylopectin is one polysaccharide of starch, can you guess what the other polysaccharide is? That's right! It is amylose. To put this in perspective, by weight more than 80% of amylopectin makes up a starch molecule.

To determine the presence of amylopectin in a soluble starch solution, the iodine test can be performed. If you see the solution turn purple after running this test, this will tell you amylopectin is present in starch. Properties of amylopectin include the fact that this molecule is known to be soluble in water. Solubility refers to the ability of amylopectin to dissolve in (or mingle with) water.

Amylopectin also has two properties that make this molecule quite popular for industry uses: bonding well with other compounds and participating in starch retrogradation. Starch retrogradation refers to starch's ability to change from a liquid solution to a gel or thickened substance. This is due to the rearrangement of glucose chains in the amylopectin molecule. These properties allow amylopectin to be used in such industry properties as the manufacturing of adhesives and lubricants.

Structure of Amylopectin

Amylopectin is built from a series of glucose units linked together by glycosidic bonds. A glycosidic bond is a covalent bond that allows the linking of two monosaccharides together. Think of a covalent bond as molecules (or atoms) that share electrons with another to form this chemical bond. A monosaccharide is simply a fancy word for a sugar molecule, such as glucose.

Given what we learned regarding the structure and formation of amylopectin, it makes perfect sense that amylopectin is a polysaccharide. It's made up of numerous monosaccharides (glucose sugar molecules) linked together by these glycosidic bonds, and the structure of amylopectin can vary in size. It can range in size from 2,000 glucose units in length to more than 200,000 units.

Another feature of amylopectin's structure is its shape. Amylopectin is a branched molecule. Think of branching like a tree where you have a straight chain (the trunk) with multiple glucose units shooting off the chain (branches). Typically, the length of an amylopectin branching chain consists of 20 to 30 glucose units.

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