Carbohydrates

Question 1

what are monosaccharides
( 1 mark)

Answer 1

monomers of which large carbohydrates are made from

Question 2

give 3 examples of monosacchrides
( 1 mark)

Answer 2

glucose
fructose
sucrose

Question 3

draw structure of a-glucose molecule
( 1 mark)

Question 4

difference between a-glucose and b-glucose ( 1 mark)

Answer 4

OH group is below crabon 1 in a-glucose but above carbon 1 in b-glucose

Question 5

what is an isomer ( 1 mark)

Answer 5

same molecular formula, diffrent structure

Question 6

what are disacchrides and how it formed
( 3 mark)

Answer 6

-2 monosacchrides joined togteher by a glycosidic bond
-formed by condensation reaction
-releasing water molecule

Question 7

what monosachrides are made of:
maltose
lactose
sucrose
( 3 mark)

Answer 7

maltose= glucose + glucose
lactose= glucose + galactose
sucrose= glucose + fructose

Question 8

what happens in condesnation reaction
( 1 mark)

Answer 8

removal of water molecules
-joined by glycosidic bond

Question 9

what happens in hydrolysis reaction
( 2 mark)

Answer 9

-adding water molecule to break bond

Question 10

what are polysacchrides and how formed
( 3 mark)

Answer 10

many monoscachrdies joined together by glycosidic bond
-formed by mnay condesnation reactions,
-releasing water molecules

Question 11

what are 3 carbon sacchrides called ( 1 mark)

Answer 11

triose

Question 12

what are 5 carbon sacchrides called ( 1 mark)

Answer 12

pentose

Question 13

what is hexose ( 1 mark)

Answer 13

6 carbon sacchrides

Question 14

5 points

test for non-reducing sugars ( 5 mark)

Answer 14

-do benedict’s test and stays blue/ negtaive
-heat in boiling water bath w/ hydrochloric acid (to hydrolyse into monosacchrides)
-neutralise with sodium hyrdogencarbonate (to neutralise alkali)
-heat in boiling water bath with benedict’s solution
-positive result= green/yellow/orange/red precipitate

Question 15

what type of disaccrhirde is tested for iwth non-reducing sugar ( 1 mark)

Answer 15

sucrose

Question 16

what type of disacchride is tested for with reducing sugars ( 1 mark)

Answer 16

maltose, lactose

Question 17

test for starch (2 marks)

Answer 17

• add 2 drops of iodine to sample in test tube and shake
  -possitve result = black-blue

Question 18

what are polysacchrides usually used for
( 2 mark)

Answer 18

storage
structure

Question 19

function of starch ( 1 mark)

Answer 19

energy store in plant cells

Question 20

structure of strach ( 3 mark)

Answer 20

-polysaccharides of a-glucose
-amylose- 1,4 glycosidic bonds (unbranched)
-amylopection- 1,6 glycosidc bonds (branched)

Question 21

function of glycogen ( 1 mark)

Answer 21

enegery store in animal cells

Question 22

structure of glycogen ( 2 mark)

Answer 22

-polysacchride of a-glucose
- 1,4 and 1,6 glycosidic bonds (branched)

Question 23

3 points

structure of starch (amylose )+ function ( 6 mark)

Answer 23

-helical—compact for storage
-insoluble—isn’t affected by water potential
-large—can’t diffuse out of cell

Question 24

4 points

structure of glycogen (starch , amylopectin)+ function ( 8 mark)

Answer 24

-branched—compact and fits more molecules in small area
-branched—more ends for faster hydrolysis (realeasing glucose for respiration)
-insoluble—isn’t affected by water potential
-large—can’t diffuse out of cell

Question 25

function of cellulose ( 1 mark)

Answer 25

provides strengh and structural suport to plant/ algae cell walls

Question 26

structure of cellulose ( 3 mark)

Answer 26

-polysacchride of b-glucose -1,4 glycosidic bonds (straight, unbranched chains) -chains linked togtehr in paraell hydorgen bonds forming microfibrils

Question 27

# 3 points cellulose structure+function ( 4 mark)

Answer 27

-b-glucose chains inverted to make long, staright, unbrached chains -many hydrogen bonds cross-linked to form microfibrils -hydrogen bonds strong in high numbers, -providing strength to cell wall

Question 28

# 3 points test for reducing sugars ( 3 mark)

Answer 28

-add benedicts solution to sample -heat in boiling wtaer bath -positive result= green/yellow/orange/red precipitate

Question 29

suggest a method to measure quanity of sugar in solution ( 3 mark)

Answer 29

-do benedicts test -filter and dry -find mass/weight

Question 30

describe the biological test for starch ( 2 mark)

Answer 30

-add iodine and shake/stir -positive result= blue-black

Question 31

suggest another method to measure the quantity of sugar in solution ( 6 mark)

Answer 31

-make sugar solutions of known concentrations (eg. dilute series) -heat each sample with benedict's solution for same time -use colorimeter to measure absorbance of each known concentration -plot calibration curve - concentration of x axis, absorbance on y axis and draw line of best fit -repeat benedict's test with unknown sample and measure absorbance -read off calibration curve to find concentration associated with unknown sample's absorbance