2.6 carbohydrates: polysaccharides

What are polysaccharides?

Polysaccharides are complex carbohydrates made up of many monosaccharides joined via glycosidic bonds.

Name three examples of polysaccharides.

Starch, glycogen, and cellulose.

What is the function of starch in plants?

To store excess glucose and release it to supply energy when needed.

What are the characteristics of starch that make it a good energy store?

1. Insoluble

2. Large

3. Many side branches

4. Coiled

5. Hydrolysis releases alpha-glucose monomers

Describe the structure of amylose.

Amylose is a long, unbranched chain of alpha glucosejoined by 1-4 glycosidic bonds, coiled into a helix.

Describe the structure of amylopectin.

Amylopectin is a long, branched chain of alpha glucosejoined by both 1-4 and 1-6 glycosidic bonds.

What is the function of glycogen in animals?

To store excess glucose and release it to supply energy when needed.

What is the structure of glycogen?

Glycogen consists of highly branched chains of alpha-glucose monomers joined by glycosidic bonds.

What are the characteristics of glycogen that make it good as an energy store?

1. Insoluble

2. Compact

3. More highly branched than starch

4. Large

5. Hydrolysis releases alpha-glucose monomers

What is cellulose?

A polysaccharide that forms the structural component of plant cell walls.

What is the function of cellulose?

To provide strength and rigidity to plant cells.

Describe the structure of cellulose. 

Cellulose is made up of beta-glucose monomers joined together via 1-4 glycosidic bonds. Every other beta-glucose monomer is inverted by 180°.

Hydrogen bonds hold individual cellulose chains together to form microfibrils. These microfibrils join together to form macrofibrils. 

What are the characteristics of cellulose that make it good at forming cell walls? 

1. Made up of long, straight, and unbranched chains 

2. Hydrogen bonds between chains 

3. Made up of microfibrils