Question

Amylopectin is composed of:
1. α-D-glucose, C₁ – C₄ and C₁ – C₆ linkage
2. β-D-glucose, C₁ – C₄ and C₂ – C₆ linkage
3. β-D-glucose, C₁ – C₄ and C₁ – C₆ linkage
4. α-D-glucose, C₁ – C₄ and C₂ – C₆ linkage

Answer 1

Correct Answer - Option 1 : α-D-glucose, C₁ – C₄ and C₁ – C₆ linkage

Concept:

Amylopectin is composed of α-D-glucose, C₁ – C₄ and C₁ – C₆ linkage.

Amylopectin is a water-soluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch. Glucose units are linked in a linear way with α(1→4) glycosidic bonds.

There are two types of glycosidic bonds, 1, 4 alpha and 1, 4 beta glycosidic bonds. 1, 4 alpha glycosidic bonds are formed when the OH on the carbon-1 is below the glucose ring; while 1, 4 beta glycosidic bonds are formed when the OH is above the plane.

Branching takes place with α(1→ 6) bonds occurring every 24 to 30 glucose units, resulting in a soluble molecule that can be quickly degraded as it has many end points onto which enzymes can attach. In contrast, amylose contains very few α(1→6) bonds, or even none at all. This causes amylose to be hydrolysed more slowly, but have higher density and be insoluble.

Starch is a polymer of α-D-glucose. It has two components.

Amylose has only α-1-glucose, 4-glycosidic linkage and is a linear polymer.

A linear polymer is a long continuous chain of carbon–carbon bonds with the remaining two valence bonds attached primarily to hydrogen or another relatively small hydrocarbon.

Amylopectin which has α-1, 6-glucosidic linkage and is a cross linked polymer.

A cross-link is a bond that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers.