disaccharides and polysaccharides

Question 1

what is a disaccharide

Answer 1

the sugar formed when 2 monosaccharides are joined by a glycosidic bond during a condensation reaction.

Question 2

what is a polysaccharide

Answer 2

macromolecules (polymers) that are formed by 3 or more monosaccharides joined by glycosidic bonds during a condensation reaction.

Question 3

what does glucose + glucose make

Answer 3

maltose

Question 4

what does glucose + galactose make

Answer 4

lactose

Question 5

what does glucose + fructose make

Answer 5

sucrose

Question 6

structure of starch

Answer 6

• plants store excess glucose as starch
• insoluble in water so doesn’t affect osmosis
• mixture of amylose and amylopectin

Question 7

structure of amylose

Answer 7

long unbranched chain for alpha glucose. compact coiled structure.
- good for storage

Question 8

structure of amylopectin

Answer 8

long branched chain of alpha glucose.
glucose can be released quickly as it is easier for enzymes to get to the branches.
- glycosidic bonds carbon 1 and 4. Also, glycosidic bonds carbon 1 and 6.

Question 9

structure of glycogen

Answer 9

lots of side branches - excellent for fast release of energy
- compact and good for storage
- 1 and 6 glycosidic bonds
animals store excess glucose as glycogen in the liver and muscles

Question 10

structure of cellulose

Answer 10

long, straight unbranched chains of beta glucose.
hydrogen bonds form between the chains forming strong fibres called microfibrils.
- structural support for cells eg. plant cell wall

Question 11

what happens to allow the bonding of the hydroxyl groups in cellulose

Answer 11

each alternate glucose molecule flips 180degrees.

Question 12

how are microfibrils strengthened in cellulose

Answer 12

chains run parallel to each other, forming microfibrils and are strengthened with cross-linkages (hydrogen bonds) between them.
gives cellulose its stability and a valuable structural material.
difficult to digest.

Question 13

what source is starch, glycogen and cellulose

Answer 13

amylose = plant
amylopectin = plant
glycogen = animal
cellulose = plant

Question 14

what bonds does starch, glycogen and cellulose have

Answer 14

amylose = 1-4
amylopectin = 1-4 and 1-6
glycogen = 1-4 and 1-6
cellulose = 1-4

Question 14

does starch, glycogen and cellulose have branches

Answer 14

amylose = no
amylopectin = yes (per 20 subunits)
glycogen = yes (per 10 subunits)
cellulose = no

Question 15

what glucose/ subunit is starch, glycogen and cellulose

Answer 15

amylose = alpha glucose
amylopectin = alpha glucose
glycogen = alpha glucose
cellulose = beta glucose

Question 16

what bonds are polysaccharides joined by

Answer 16

glycosidic

Question 17

why is starch and glycogen good for storage

Answer 17

• they are compact = large quantities can be stored
• they are insoluble = no osmotic effect

Question 18

when is the glycosidic bond broken

Answer 18

when water is added in hydrolysis