Starch, Glycogen and Cellulose

Question 1

Where is starch found and in what form?

Answer 1

Starch is found in plants, in the form of 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 made formed from two glucose polymers, amylose and amylopectin. Fundamentally formed from alpha glucose

Question 4

What is amylose?

Answer 4

Amylose is a glucose polymer formed from alpha glucose monomers, consisting of 1,4 glycosidic bonds

Question 5

Describe amylose’s structure

Answer 5

Amylose has an unbranched shape that forms a helical structure

Question 6

How does amylose’s 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 glucose polymer consisting of (1,4) and (1,6) glycosidic bonds

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 has a branched structure that increases its surface area and allows for rapid hydrolysis of starch into glucose

Question 9

Glucose is converted into starch for storage within plant cells

Describe the reaction that occurs for this to happen

Answer 9

The reaction that occurs is a condensation reaction. This involves glucose molecules forming (1,4) and (1,6) glycosidic bonds with each other. With this there is an elimination of water molecules at the end of the chemical reactions

Question 10

What is starch composed of that affects its structure and how does this structure help with starch’s function?

Answer 10

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 11

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

Answer 11

Amylose makes up to 10-30% of starch

Amylopectin makes up to 70-90% of starch

Question 12

What is glycogen formed from? How is glycogen formed?

Answer 12

Glycogen is made from alpha glucose molecules. The alpha glucose molecules join together through multiple condensatio reactions. This results in (1,4) and (1,6) gylcosidic bonds forming, with the elimination of a water molecule each time.

Question 13

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

Answer 13

1. Starch is an insoluble molecule so it doesn’t affect water potential
2. Starch has a helical structure making it more compact so it can fit many molecules into a small area

Question 14

Describe glycogen’s structure

Answer 14

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

Question 15

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

Answer 15

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 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

Glycogen’s main function is to store glucose

Question 17

What is cellulose?

Answer 17

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

Question 18

How does cellulose form its glycosidic bonds between its beta glucose monomers?

Answer 18

Cellulose forms its glycosidic bonds between the beta glucose monomers through multiple condensation reactions. The beta glucose monomers must be rotated 180 degrees opposite to each other, prior to these reactions

Question 19

Where is cellulose found?

Answer 19

Cellulose is found in plants cells, specifically their cell walls

Question 20

Describe cellulose’s structure

Answer 20

Cellulose is composed of beta glucose monomers which form long, straight chains which are held in parallel to each other by hydrogen bonds forming fibrils

Question 21

Why are beta glucose molecules rotated to 180 degrees to each other in cellulose?

Answer 21

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

Question 21

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

Answer 21

1. Cellulose is made up of beta glucose molecules and glycogen is made from alpha glucose molecules
2. Cellulose has long straight chains and glycogen has a branched structure
3. Glycogen has (1,4) and (1,6) glycosidic bonds and cellulose only has (1,4) glycosidic bonds

Question 22

How does cellulose 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

Starch and cellulose are two important plant polysaccharides

Explain the difference in structure of the starch molecule and the cellulose molecule

Answer 23

1. Starch has a helical structure whereas cellulose has long, straight chains forming its structure
2. Starch is composed of (1,4) and (1,6) glycosidic bonds whereas cellulose is composed of just (1,4) glycosidic bonds