Exam specific answers

Question 1

explain 1 way in which starch molecules are adapted for their function in plant cells (storage substance)? (2)

Answer 1

insoluble so they don’t affect water potential
helical structure so compact
large molecule so cannot leave cell

Question 2

explain how cellulose molecules are adapted for their function in plant cells? (3)

Answer 2

they are made up of long and straight chains which become linked by many hydrogen bonds to form fibrils, so they provide strength to the cell wall

Question 3

in what ways is the structure of cellulose different to the structure of starch? (5)

Answer 3

starch/cellulose
alpha glucose/beta glucose
branched/unbranched
helical/straight
no microfibrils/has microfibrils
all glucoses same way up/alternate glucoses are upside down

Question 4

state two differences between the structure of cellulose and starch? (2)

Answer 4

cellulose is made up of β-glucose and glycogen is made up of α-glucose
cellulose molecule has straight chain and glycogen is branched
glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds

Question 5

why do red blood cells have a higher percentage by mass of cholesterol than ileum cells? (1)

Answer 5

red blood cells are not supported by other cells, so the cholesterol helps them to maintain their shape

Question 6

describe a test to show that raffinose solution contains a non-reducing sugar? (3)

Answer 6

1. heat with acid and neutralise
2. heat with Benedict’s solution
3. red precipitate/colour will form