carbohydrates - polysaccharides

Question 1

starch consists of 2 polymers what are they called

Answer 1

amylose and amylopectin

Question 2

which isomer of glucose is the monomer of starch

Answer 2

alpha glucose

Question 3

what makes starch useful as a storage compound of glucose

Answer 3

as its insoluble which makes it osmotically neutral its in a coiled structure which makes it compact which allows efficient storage of large amounts in a small area

Question 4

where is glycogen stored

Answer 4

in the liver and skeletal muscles

Question 5

what is the significance of the highly branched nature of glycogen

Answer 5

As it is branched it means there are many free ends which are able to rapidly store and realise glucose as needed

Question 6

which isomer of glucose is the monomer cellulose

Answer 6

beta glucose

Question 7

what properties of cellulose make is suitable for the cell wall of plants

Answer 7

as its unbranched it has a high tensile strength and they are able to form tough fibres called microfibrils

Question 8

what are the similarities and differences between chitin and cellulose

Answer 8

-They are both a structural polysaccharides
- they both form beta 1-4 chains
- they are both rooted 180 degrees in relation to the monomer next to each other
-both form long parallel chains that are cross linked to each other by hydrogen bond to form microfibrils
-chitin is found in the exoskeleton of insects whereas cellulose is found in cell walls

Question 9

where would you find chitin

Answer 9

in the exoskeleton of insects

Question 10

what the name of the test for starch

Answer 10

iodine potassium iodine test

Question 11

describe the test for starch

Answer 11

iodine solution reacts with starch which results in a colour change from orange- brown to blue-black

Question 12

what is iodine solution

Answer 12

iodine dissolved in an aqueous solution of potassium iodide

Question 13

what is the colour change observed if starch is present from the iodine test

Answer 13

colour change from orange-brown to blue-black

Question 14

what type of tests is the iodine test and why

Answer 14

its a qualitative test as an accurate concentration can’t be determined but the depth of the blue-black colour can indicate the relative concentration

Question 15

what are polysaccharides

Answer 15

they are large complex polymers formed my a large number of monosaccharide units linked by a glycosidic bond

Question 16

why does glucose have to be stored in an appropriate form

Answer 16

as it is soluble in water so it would increase the concentration of the cell contents and therefore draw water in by osmosis

Question 17

why is glucose converted into a storage product

Answer 17

as it means that it will no longer be soluble so it can’t draw water in by osmosis and increase the concentration in the cell

Question 18

why is storage a good storage molecule of glucose

Answer 18

• as its insoluble so it is osmotically neutral
  -can’t diffuse out the cell
  -its compact so can be stored in small spaces
  -carries a lot of energy due to its C-H and C-C bonds

Question 19

where is starch found

Answer 19

in high concentrations in seeds and storage organs

Question 20

describe amylose

Answer 20

-linear unbranched molecule
-alpha 1-4 glycosidic bonds
-coils into a helix

Question 21

describe amylopectin

Answer 21

-has alpha 1-4 glycosidic bonds with alpha 1-6 cross linkages
-branched molecule

Question 22

what is the main storage product in animals

Answer 22

glycogen

Question 23

how is glycogen similar to amylopectin

Answer 23

it has alpha 1-4 and 1-6 bonds

Question 24

how is glycogen different to amylopectin

Answer 24

glycogen molecules have shorter alpha 1-4 linked chains so glycogen is more branched that amylopectin

Question 25

what's role does cellulose have

Answer 25

cellulose is a structural polysaccharide and is present in cell walls

Question 26

describe the structure of cellulose

Answer 26

-long parallel chains of beta glucose -monomers a joined by beta 1-4 glycosidic bonds -each monomer rotates 180 degrees to the adjacent one

Question 27

why are glucose molecules in cellulose coated 190 degrees to the adjacent one

Answer 27

as it allows hydrogen bonds to from between the OH groups of adjacent parallel chains and contributes to celluloses structural stability

Question 28

how are microfibrils formed

Answer 28

when 60 to 70 cellulose molecules become tightly cross linked

Question 29

why are microfibrils important in the cell wall

Answer 29

as microfibrils are held in bundles called fibres and a cell wall has several layers of fibres which contributes to the strength of the cell wall

Question 30

why are cellulose fibres freely permeable

Answer 30

as there are spaces between the fibres

Question 31

as cellulose is freely permeable what does this allow

Answer 31

water and its solutes can penetrate through the spaces in the cell wall to the cell membrane

Question 32

role of chitin

Answer 32

chitin is a structural polysaccharide which is found in the exoskeletan of insects and fungal cell walls

Question 33

structure of chitin

Answer 33

-long chains of beta 1-4 linked monomers and has derived groups of amino acids added

Question 34

what do they derived groups of amino acids added to the long chains of beta 1-4 monomers in chitin form

Answer 34

heteropolysaccharide

Question 35

properties of chitin related to its function

Answer 35

strong, lightweight and waterproof

Question 36

how is chitin similar to cellulose

Answer 36

the monomers are also rotated 180 degrees in relation to their neighbour and also form microfibrils