Question

Which two polysaccharides share all of their glycosidic linkage types in common? (A) Cellulose and amylopectin (B) Amylose and glycogen (C) Amylose and cellulose (D) Glycogen and amylopectin

Short answer

Option D: Glycogen and amylopectin.

Step-by-step solution

- Understanding Glycosidic Linkage Types Involved

Identify the common types of glycosidic linkages in polysaccharides. The main types are α(1→4) and α(1→6) for storage polysaccharides like amylopectin and glycogen, and β(1→4) for structural polysaccharides like cellulose.

- Analyzing Glycosidic Linkages in Cellulose

Cellulose primarily consists of β(1→4) glycosidic linkages, which contribute to its rigid structure.

- Analyzing Glycosidic Linkages in Amylose

Amylose consists of α(1→4) glycosidic linkages. It is an unbranched polysaccharide found in starch.

- Analyzing Glycosidic Linkages in Amylopectin

Amylopectin is a branched polysaccharide with α(1→4) glycosidic linkages in the backbone and α(1→6) linkages at the branch points.

- Analyzing Glycosidic Linkages in Glycogen

Glycogen is similar to amylopectin but more highly branched. It also contains α(1→4) glycosidic linkages in the backbone and α(1→6) linkages at the branch points.

- Identifying Polysaccharides that Share Glycosidic Linkages

Compare the glycosidic linkage types. Amylopectin and glycogen share both α(1→4) and α(1→6) linkages.

- Selecting the Correct Option

From the analysis, the two polysaccharides that share all of their glycosidic linkage types in common are glycogen and amylopectin.

Key concepts

Glycosidic Linkages

Glycosidic linkages are bonds that connect sugar molecules to form polysaccharides. They are crucial for the structure and function of these large biomolecules.
Glycosidic linkages can vary in type, including α-linkages and β-linkages. These variations affect how the polysaccharide behaves.

• α(1→4) linkages: Found in storage polysaccharides like amylose, amylopectin, and glycogen. They connect carbon 1 of one sugar to carbon 4 of another.
• α(1→6) linkages: Create branches in polysaccharides such as amylopectin and glycogen. These link carbon 1 of one sugar to carbon 6 of another.
• β(1→4) linkages: Found in structural polysaccharides like cellulose. These connect carbon 1 of one sugar to carbon 4 of another, but in a different orientation compared to α-linkages.

Understanding these linkages helps in identifying similarities and differences between various polysaccharides.

Polysaccharide Structure

Polysaccharides are large molecules composed of many sugar units joined by glycosidic linkages. The structure of these polysaccharides determines their function.
These can be linear or branched, impacting their solubility and how they store energy.
Key points:

• Linear polysaccharides like amylose have no branches, making them more compact.
• Branched polysaccharides like amylopectin and glycogen have multiple branching points, making them more accessible for energy release due to more ends for enzyme action.
• Cellulose is linear but forms strong fibers due to hydrogen bonding between chains, providing structural support in plants.

Recognizing these structural differences helps understand why certain polysaccharides serve specific roles in organisms.

Amylopectin

Amylopectin is a branched polysaccharide found in plants. It is a major component of starch, along with amylose.
Amylopectin's structure:

• Backbone of α(1→4) glycosidic linkages.
• Branches with α(1→6) glycosidic linkages occurring every 24-30 glucose units.

This branching structure makes amylopectin highly soluble and more easily broken down by enzymes compared to linear structures.
Amylopectin is important for quick energy release due to its many branch points, providing multiple sites for enzymatic action.

Glycogen

Glycogen is a polysaccharide that serves as a primary storage form of glucose in animals and fungi.
Its structure is similar to amylopectin but more highly branched:

• Backbone of α(1→4) glycosidic linkages.
• Branches with α(1→6) linkages occurring approximately every 8-12 glucose units.

This extensive branching makes glycogen an even more efficient storage molecule than amylopectin, allowing for rapid release of glucose when needed.
Glycogen's structure ensures that animals can quickly access stored energy during high demand periods such as exercise or between meals.