Polysaccharides

Question 1

What are the features of energy storage molecules

Answer 1

They are compact - energy dense
They are insoluble - so they don’t affect the water potential for the cell
Easy to add glucose to - condensation reaction
Easy to remove glucose from - hydrolysis
Metabolically inactive

Question 2

Where is starch found

Answer 2

Starch is found in chloroplasts and in membrane bound starch grains

Question 3

Where is glycogen found

Answer 3

Glycogen is found in the liver

Question 4

What are starch and glycogen

Answer 4

Two polysaccharides made from glucose

Question 5

What is amylose

Answer 5

Amylose is a polysaccharide that contains glucose molecules joined mainly by 1-4 glycosidic bonds

Question 6

What is the structure of amylose and why

Answer 6

a 1-4 glycosidic bonds resulting in unbranched chains forming a compact helical structure

Question 7

What is the structure of amylopectin

Answer 7

Amylopectin also contains glucose molecules joined by a 1-4 glycosidic bond but it also has a 1-6 glycosidic bond resulting in amylopectin having a highly branched structure.

Question 8

What percentage of starch is made up by amylose

Answer 8

30% of starch

Question 9

What is amylose held together by

Answer 9

Its spiral shape is held in place by hydrogen bonds.

Question 10

Where are the OH groups in amylose

Answer 10

They are inside the coil making amylose less soluble as these are the groups that would hydrogen bond with water.

Question 11

What percentage of starch is amylopectin

Answer 11

70%

Question 12

what is the structure of amylopectin in starch

Answer 12

It coils into a spiral shape, and is held together with hydrogen bonds, but with branches emerging from the spiral.

Question 13

Why is the structure of amylopectin good for a storage molecule

Answer 13

it provides multiple sites for hydrolysis allowing glucose to be removed quickly

Question 14

What is glycogen made from

Answer 14

It is made of glucose

Question 15

how is glycogen stored

Answer 15

it is stored as small granules particularly in the muscles and liver

Question 16

What are the branch points in glycogen from

Answer 16

they are from the 1-6 glycosidic bond

Question 17

what is the comparison between glycogen and starch

Answer 17

It is more coiled and compact than amylopectin. Indicating a higher metabolic rate of animals compared to plants.

Question 18

What is cellulose used for

Answer 18

It is the main component of plant cell walls

Question 19

What are the properties of cellulose

Answer 19

They are insoluble, have a high tensile strength, unreactive and flexible

Question 20

What is the structure of cellulose

Answer 20

The glucose molecules are linked together by a beta 1-4 glycosidic bond. However, every other glucose molecule rotates 180 degrees so that the hydroxyl groups on each molecule are adjacent to each other.

Question 21

What does this bonding mean for cellulose

Answer 21

It results in long unbranched chains, the hydrogen bonding between chains gives cellulose molecules great tensile strength which is ideal for supporting plant cells.

Question 22

What do 60-70 cellulose chains do together

Answer 22

They bind together to form microfibrils

Question 23

What do 400 microfibrils do

Answer 23

They bundle together to form macrofibrils

Question 24

How do macrofibrils increase their tensile strength

Answer 24

They join in all directions criss-crossing the wall for extra tensile strength.

Question 25

Why is the tensile strength of cellulose important

Answer 25

To support the plant
To prevent cells from bursting when turgid and to protect the cell membrane

Question 26

what is another property of the cell wall

Answer 26

It is fully permeable due to space between macrofibrils.