3.3 &3.4 testing for carbohydrates

Question 1

whats a condensation reaction

Answer 1

its a reaction which joins monomers by chemical bonds and a water molecule is removed

Question 2

whats hydrolysis

Answer 2

a water molecule is added to break a chemical bond between two molecules

Question 3

examples of monomers

Answer 3

nucleotides
amino acids
monossacharides

Question 4

what is a monomer

Answer 4

a small unit which makes up larger molecules

Question 5

whats a polymer

Answer 5

molecules made up from monomers joined together

Question 6

what elements do carbohydrates consist of

Answer 6

carbon
hydrogen
oxygen

Question 6

what are carbohydrates

Answer 6

long chains of sugar units a called saccharides

Question 7

what type of bond is found in carbohydrates

Answer 7

glycosidic bonds

Question 8

what are the three types of saccharides

Answer 8

monosaccharides
disaccharides
polysaccharides

Question 9

how do monosaccharides join together to make disaccharides and polysaccharides

Answer 9

by glycosidic bonds in condensation reactions

Question 10

how many carbons does glucose contain

Answer 10

6

Question 11

what are the two isomers of glucose

Answer 11

alpha glucose and beta glucose

Question 12

what is the disaccharide maltose made up of

Answer 12

two glucose molecules

Question 13

what is the disaccharide sucrose made up of

Answer 13

glucose and fructose

Question 14

what is the disaccharide lactose made up of

Answer 14

glucose and galactose

Question 15

whats the function of glycogen

Answer 15

its the main energy store in animals

Question 16

what bonds does glycogen contain and what glucose is it made up of

Answer 16

1,6 and 1,4 glycosidic bonds between alpha glucose

Question 17

how is glycogen adapted for its function

Answer 17

lots of side branches so glucose can be rapidly hydrolysed to release energy quickly.
and it is a relatively large but compact molecule so can store more glucose
and isn’t water soluble so doesn’t affect water potential

Question 18

what is the function of starch

Answer 18

to store energy in plants

Question 19

starch is a mixture of what two polysaccharides

Answer 19

amylopectin and amylose

Question 20

what bonding is present between what glucose molecules in amylose

Answer 20

1,4 glycosidic bonds between alpha glucose

Question 21

whats the structure of glycogen like

Answer 21

highly branched molecule

Question 22

whats the structure of amylose like

Answer 22

unbranched coiled compact molecule

Question 23

how is amylose adapted for its function

Answer 23

its compact so can store more glucose and isnt water soluble so doesnt affect water potential

Question 24

what bonding is present between what molecules in amylopectin

Answer 24

1,6 and 1,4 glycosidic bonds in alpha glucose

Question 25

whats the structure of amylopectin like

Answer 25

a branched molecule

Question 26

how is amylopectin adapted for its function

Answer 26

its branched so can be rapidly hydrolysed to release glucose and isnt water soluble so doesnt affect water potential

Question 27

whats the function of cellulose

Answer 27

it provides structure in plant cells, its a component of cell walls

Question 28

why can beta molecules join together the same way alpha molecules can

Answer 28

the hydroxyl groups on carbons 1 and 4 are too far apart to react so two beta molecules can only react if one is turned upside down

Question 29

whats the structure of cellulose like

Answer 29

its straight chains held parallel by hydrogen bonds

Question 30

what bonds hold what molecules together in cellulose

Answer 30

1,4 glycosidic bonds together beta molecules

Question 31

when beta molecules are joined via condensation reaction why does it form cellulose not starch

Answer 31

as the alternate beta has to be joined upside down as the hydroxyl gorups on C 1&4 wouldnt be close enough otherwise, when they are joined this way they are unable to coil or form branches so a straight chained molecule is formed

Question 32

what does cellulose molecules join by hydrogen bonds to form

Answer 32

microfibrils

Question 33

what do microfibrils join to form

Answer 33

macrofibrils

Question 34

whats the test for reducing sugars

Answer 34

using benedicts reagent which is alkaline copper (11) sulphate which is added in equal parts to the sample then heated in a water bath

Question 35

what shows a positive test for reducing sugars

Answer 35

blue to brick red as the reducing sugar adds electrons and reduces the blue Cu2+ ions to brick red Cu+ ions a brick red precipitate is formed

Question 36

whats the test for non reducing sugars

Answer 36

they dont react with benedicts so have to be boiled with NaOH first then warmed with benedicts solution as non reducing sugars eg sucrose has to be hydrolysed to reducing sugars eg glucose and sucrose

Question 37

whats the test for starch

Answer 37

iodine test a few drops of iodine solution are mixed with potassium iodide solution

Question 38

whats the positive test for starch

Answer 38

yellow/brown to purple/black

Question 39

what do reagent strips test for

Answer 39

the presence of reducing sugars commonly glucose

Question 40

what does a colorimeter do

Answer 40

it quantitively measures the absorbance of light by a colored solution this can be used to determine the concentration of glucose in a solution

Question 41

what do biosensors do

Answer 41

they determine the presence and concentration of molecules such as glucose

Question 42

whats the analyte in a biosensor

Answer 42

the compound under investigation

Question 43

what are the three stages in using a biosensor

Answer 43

molecular recognition (a protein or ssDNA is immobilised to a surface eg glucose test this will interact with or bind to compound under investigstion) transduction (the interaction in the molecular recognition stage will cause a change in a transducer which detects the change and produces a response eg relseasing dye on test strip) display (this procuces a visable signal eg colour on test strip)