Carbohydrates

Question 1

what is a condensation reaction?

Answer 1

joining monomers by a covalent bond, by removing water

Question 2

what is a hydrolysis reaction?

Answer 2

splitting of 2 monomers, by adding water

Question 3

what is a covalent bond?

Answer 3

sharing of electrons between 2 or more atoms

Question 4

what does a polar and non-polar bond mean?

Answer 4

polar = equally shared electrons
non-polar = unequally shared electrons (more electronegative)

Question 5

are covalent bonds strong?

Answer 5

yes because they’re stable so require a lot of energy to break

Question 6

what is a reducing sugar?

Answer 6

they donate electrons and sugar is the reducing agent

Question 7

what is a non-reducing sugar?

Answer 7

they can’t donate electrons so can’t be oxidised

Question 8

give 3 examples of a reducing sugar

Answer 8

maltose, fructose, galactose or glucose

Question 9

give an example of a non-reducing sugar

Answer 9

sucrose

Question 10

what is an isomer?

Answer 10

same molecular formula but different structural formula (therefore different properties)

Question 11

how do you test for a reducing sugar?

Answer 11

Add benedict’s reagent, heat in a water bath.
Positive result - brick-red
eg. soluble copper sulfate is reduced to insoluble copper oxide

Question 12

how do you test for a non-reducing sugar?

Answer 12

Add HCl to break disaccharide into 2 monosaccharides add sodium hydrogencarbonate to neutralise acid, add benedict’s reagent and heat in water bath
positive result - brick-red

Question 13

what is starch (amylose and amylopectin) formed from?

Answer 13

a glucose

Question 14

what is glycogen formed from?

Answer 14

a glucose

Question 15

what is starch for?

Answer 15

storage in plants
- granules in plastids

Question 16

what is glycogen for?

Answer 16

storage in animals and fungi

Question 17

is amylopectin branched?

Answer 17

yes

Question 18

is amylose branched?

Answer 18

no

Question 19

is glycogen branched?

Answer 19

yes (most branched)

Question 20

is amylose in a coiled helix?

Answer 20

yes

Question 21

is amylopectin in a coiled helix?

Answer 21

no

Question 22

what type of glycosidic bond does amylose contain?

Answer 22

1,4 (unbranched and compact)

Question 23

is glycogen in a coiled helix?

Answer 23

no

Question 24

what type of glycosidic bond does amylopectin contain?

Answer 24

1,4 and 1,6 (branched)

Question 25

what type of glycosidic bond does glycogen contain?

Answer 25

1,6

Question 26

what is cellulose formed from?

Answer 26

B glucose

Question 27

what type of glycosidic bonds are in cellulose?

Answer 27

1,4 (rotate 180° to join)

Question 28

why is cellulose so strong?

Answer 28

• there are lots of H bonds due to the rotation
• cellulose fibres and other molecules form a matrix
• stretch without breaking

Question 29

what is a disaccharide?

Answer 29

when 2 monosaccharides are joined in a condensation reaction by a glycosidic bond

Question 30

give 3 examples of a disaccharide

Answer 30

lactose, maltose and sucrose

Question 31

what is maltose made from?

Answer 31

2x a glucose molecules (1,4 bond)

Question 32

what is sucrose made from?

Answer 32

a glucose + fructose (1,2 bond)

Question 33

what is lactose made from?

Answer 33

a glucose + galactose

Question 34

give 3 examples of a monosaccharide

Answer 34

glucose, galactose and fructose

Question 35

give 3 examples of a polysaccharide

Answer 35

starch, glycogen and cellulose