Polysaccharides

Question 1

What polysaccharides do we need to know about?

Answer 1

• Starch
• Glycogen
• Cellulose

Question 2

What do we need to know about the three polysaccharides?

Answer 2

The relationship between their structures and functions.

Question 3

Where do cells get energy from?

Answer 3

Glucose.

Question 4

What are polysaccharides?

Answer 4

Carbohydrates.

Question 5

What are polysaccharide molecules made from?

Answer 5

Large numbers of their monomers (monosaccharides).

Question 6

When is a polysaccharide formed?

Answer 6

When more than two monosaccharides are joined together by condensation reactions.`

Question 7

How are polysaccharides broken down?

Answer 7

By hydrolysis reactions

Question 8

Within what type of organism is starch relevant?

Answer 8

Within plants.

Question 9

Why is starch relevant to plants?

Answer 9

Because plants store excess glucose as starch.

Question 10

What happens when plants need more energy?

Answer 10

They break down starch to release the glucose.

Question 11

What is starch made of?

Answer 11

Two polysaccharides of alpha glucose.

Question 12

What two polysaccharides of alpha glucose is starch made from?

Answer 12

• Amylose

* Amylopectin

Question 13

What is the structure of amylose?

Answer 13

• Long
• Unbranched
• Chain of alpha glucose
• Coiled (like a cylinder)

Question 14

What is the structure of amylopectin?

Answer 14

• Long
• Branched
• Chain of alpha glucose

Question 15

Why is amylose good for storage?

Answer 15

Its compact, due to its coiled structure. (you can fit more in a small space).

Question 16

How does amylose have a coiled structure?

Answer 16

Because of the angles of its glycoscidic bonds.

Question 17

Why is amylopectin good for storage?

Answer 17

Glucose can be released quickly, due to its side branches.

Question 18

How is glucose released easily in amylopectin?

Answer 18

Because the enzymes that hydrolyse the molecule can get at the glycoscidic bonds easily.

Question 19

Why is starch itself good for storage?

Answer 19

Because it is insoluble in water thus is doesn’t affect water potential.

Question 20

Why is starch being insoluble in water good for storage?

Answer 20

Because it doesn’t cause water to enter cells by osmosis.

Question 21

Within what type of organism is glycogen relevant?

Answer 21

Animals.

Question 22

Why is glycogen relevant to animals?

Answer 22

Animals store excess glucose as glycogen.

Question 23

What is the structure of glycogen?

Answer 23

• Long
• Branched
• Chain of alpha glucose

Question 24

What molecule is glycogen similar to?

Answer 24

Amylopectin, except it has lots more side branches coming off it.

Question 25

Why is glycogen good for storage?

Answer 25

* Stored glucose can be released quickly. | * Compact molecule.

Question 26

What does glycogen look like?

Answer 26

image

Question 27

What does amylose look like?

Answer 27

image

Question 28

What does amylopectin look like?

Answer 28

image

Question 29

Within what is cellulose relevant to?

Answer 29

Cells (cell walls).

Question 30

Why is cellulose relevant to cells?

Answer 30

Because it provides structural support for cell walls.

Question 31

How does cellulose provide structural support for cell walls?

Answer 31

Because they form strong fibres called microfibrils.

Question 32

What is the structure of cellulose?

Answer 32

* Long * Unbranched * Chain of beta glucose

Question 33

How does cellulose form microfibrils?

Answer 33

* Because when the beta glucose molecules bond, they form straight cellulose chains. * These chains are linked together by hydrogen bonds.

Question 34

What does cellulose look like?

Answer 34

image

Question 35

How do you test for the presence of starch in a sample?

Answer 35

The iodine test for starch.

Question 36

What does the iodine test, test for?

Answer 36

Starch

Question 37

How do you carry out the iodine test for starch?

Answer 37

Add iodine dissolved in potassium iodide solution to the sample.

Question 38

What result occurs when starch is present during the iodine test?

Answer 38

The sample changes from browny-orange to a dark bluey-black colour.

Question 39

What happens when starch is not present in the sample?

Answer 39

The sample stays browny-orange.

Question 40

What does the iodine test for starch look like?

Answer 40

image