Starch, Glycogen and Cellulose

Question 1

Where is starch found and in what form?

Answer 1

Starch is found in plants and is found in small granules or grains

Question 2

Why is starch important?

Answer 2

Starch is an important component in food and is a major energy source in most diets

Question 3

What is starch made from?

Answer 3

Starch is formed from two glucose polymers, amylose and amylopectin. Fundamentally formed from alpha glucose.

Question 4

What is amylose?

Answer 4

Amylose is a polymer. It consists from 1,4 glycosidic bonds and unbranched helical structure

Question 5

Describe amylose’s structure

Answer 5

Amylose has an unbranched shape that forms a helical structure

Question 6

How does amylose structure help with its functions?

Answer 6

Amylose’s unbranched helical structure allows starch to store a lot of glucose in a small space

Question 7

What is amylopectin?

Answer 7

Amylopectin is a polymer consisting of (1,4) and (1,6) glycosidic bonds made from alpha glucose molecules

Question 8

Describe amylopectin’s structure

Answer 8

Amylopectin has a branched structure consisting of (1,4) and (1,6) glycosidic bonds

Question 9

How does amylopectins structure help with its function?

Answer 9

Amylopectin’s has a branched structure that increases it surface area and allows for rapid hydrolysis of starch into glucose

Question 10

Glucose is converted into starch for storage within plant cells

Describe the reaction that occurs for this to happen

Answer 10

Glucose converting into starch is an example of a condensation reaction. This involves glucose molecules forming (1,4) and (1,6) glycosidic bonds with eachother. As well as the elimination of water molecules at the end of the chemical reactions

Question 11

How does starch’s structure help with its function?

Answer 11

Starch is composed of amylose and amylopectin. The helical shape of amylose makes starch more compact allowing it to fit a lot of glucose in a small space. The branched structure of amylopectin increases the surface area and allows for rapid hydrolysis of starch to glucose for use in plant cells.

Question 12

How much amylose and amylopectin make up of starch (percentages)?

Answer 12

Amylose is makes up 10-30% of starch
Amylopectin makes up 70-90% of starch

Question 13

What is glycogen made from?

Answer 13

Glycogen is made from alpha glucose. The alpha glucose is bonded by few 1,4 glycosidic bonds and many 1,6 glycosidic bonds

Question 14

Describe glycogen’s structure

Answer 14

Glycogen has a highly branched structure, even more branched than amylopectin

Question 15

Where is glycogen found?

Answer 15

Glycogen is found in animal cells mainly in the muscles/liver

Question 16

What is glycogens main function

Answer 16

To store glucose

Question 17

How does glycogen’s structure help with its function? Why is its structure important in animals?

Answer 17

Glycogen’s highly branched structure allows for rapid hydrolysis of glycogen into glucose. This is important for animals as they move a lot and require more energy.

Question 18

What is cellulose?

Answer 18

Cellulose is a polysaccharde. Consisting of long chains of beta glucose joined by 1,4 glycosidic bonds

Question 19

How does cellulose form its glycosidic bonds between their beta glucoses

Answer 19

To form celluloses 1,4 glycosidic bonds, beta glucose molecules must be rotated 180 degrees to eachother

Question 20

Where is cellulose found?

Answer 20

Cellulose is found in plant cells, their cell walls

Question 21

Describe cellulose structure

Answer 21

Cellulose forms long, straight chains which are held in parallel to each other by hydrogen bond forming fibrils

Question 22

How does celluloses structure help with its functions?

Answer 22

Cellulose has long chains that are held in parallel to each other by their hydrogen bonds providing strength for their cell wall

Question 23

Why are the beta glucose molecules rotated 180 degrees to eachother in cellulose?

Answer 23

The beta glucose molecules must be rotated at 180 degrees relative to each other so the glycosidic bonds to form

Question 24

Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and glycogen molecule

Answer 24

Cellulose is made up of beta glucose molecules and glycogen is made from alpha glucose molecules

Cellulose has long straight chains and glycogen is branched

Glycogen has (1,4) and (1,6) glycosidic bonds and cellulose has (1,4) glycosidic bonds

Question 25

Starch is a carbohydrate often stored in plant cells
Describe and explain two features of starch that make it a good storage molecule

Answer 25

1. Starch is insoluble so it doesn’t affect water potential
2. Starch has a branched structure so makes the molecule more compact
3. Starch has a branched structure so it can fit many molecules in a small area
4. Starch is a large molecule so it cannot cross the cell membrane

Question 26

Starch and cellulose are two important plant polysaccharides

Explain the difference in the structure of the starch molecule and the cellulose molecule shown in the diagram above

Answer 26

1. Starch is formed from alpha glucose molecules but cellulose is formed from beta glucose
2. The positioning of the hydrogen and hydroxyl group on the carbon atom 1 is inverted