Polysaccarides- starch, cellulose, glycogen

Starch, Glycogen and Cellulose

What is the main purpose of starch?

The main energy storage material in plants.

Where do cells get energy from?

They get energy from glucose. Plants store the excess glucose as starch, and break it back down into glucose as needed.

What is starch made up of?

It is a mixture of two polysaccharides of alpha-glucose. AMYLOSE and AMYLOPECTIN

Describe amylose

A long, unbranched chain of alpha-glucose. It has a coiled structure, which makes it compact, so it is good for storage because you can fit more in a small space.

Describe amylpectin

A long, branched chain of alpha-glucose. Its branches allow the enzymes that break down the molecule to access the glycosidic bonds easily. This means glucose can be released quickly.

Why is starch so well adapted for storage?

Because it is insoluble in water and doesn't affect water potential, it doesn't cause water to enter cells by osmosis, which could make them swell.

How do you test for starch?

You do the iodine test.
1) You would add iodine dissolved in potassium iodide solution to a test sample
2)If starch is present, the sample will change from brown-orange to a dark blue, black colour.

How does the storage of glucose differ in animals?

In animals, glucose is stored as glycogen. A different polysaccharide of alpha-glucose

How is the structure of glycogen different to amylopectin?

It is similar in that is has branches, but it has significantly more than amylopectin, meaning that glucose can be released quickly

Why is glycogen good for storage?

It is very compact.

What is the major component in plant cell walls?

Cellulose

What is cellulose?

A long, unbranched chain of beta-glucose, which form straight cellulose chains

How are cellulose chains linked together?

By hydrogen bonds to form strong fibres called microfibrils

How d microfibrils help plants?

They provide structural support for the cell walls.