1.1 (monomers and polymers) + 1.2 (carbohydrates)

Question 1

Define monomer. Give some examples

Answer 1

Smaller units that join together to form larger molecules.

Monosaccharides (glucose,fructose,galactose)
Amino acids
Nucleotides

Question 2

Define polymer. Give some examples

Answer 2

Molecules formed when many monomers join together

Polysaccharide
Proteins
DNA/RNA

Question 3

What happens in a condensation reaction

Answer 3

A chemical bond forms between 2 molecules and a molecule of

water is produced

Question 4

What happens in a hydrolysis reaction?

Answer 4

A water molecule is used to break a chemical bond between 2 molecules

Question 5

Name 3 hexose monosaccharides

Answer 5

Glucose
Fructose
Galactose

All have the molecular formula C6H12O6

Question 6

Name the type of bond formed when monosaccharides react

Answer 6

1,4 or 1,6 glycosidic bond

2 monomers = 1 chemical bond = disaccharide

Multiple monomers = many chemical bonds = polysaccharide

Question 7

Name 3 disaccharides. Describe how they form

Answer 7

Condensation reaction forms glycosidic bond between 2 monosaccharides

Maltose: glucose + glucose
Sucrose:glucose + fructose
Lactose: glucose + galactose

All have molecular formula C12H22O11

Question 8

Draw the structure of alpha glucose

Answer 8

Slide 17

Question 9

Draw the structure of beta glucose

Answer 9

Slide 20

Question 10

Describe the structure and functions of starch

Answer 10

Storage polymer of alpha glucose in plant cells

Insoluble = no osmotic effect on cells
Large = does not diffuse out of cells

Made from amylose:
1,4 glycosidic bonds
Helix with intermolecular H-bonds making it compact

Made from amylopectin:
1,4 and 1,6 glycosidic bonds
Branched so the are many terminal ends for hydrolysis into glucose

Question 11

Describe the structure and functions of glycogen

Answer 11

Main storage polymer of alpha glucose in animal cells but also found in plant cells

1,4 and 1,6 glycosidic bonds
Branched = many terminal ends for hydrolysis
Insoluble = no osmotic effect and does not diffuse out of cells
Compact

Question 12

Describe the structure and functions of cellulose

Answer 12

Polymer of beta glucose gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)

1,4 glycosidic bond
Straight chain, unbranched molecule
Alternate glucose molecules are rotated 180 degree
H-bond cross links between parallel strands form microfibrils = high tensile strength

Question 13

Describe Benedict’s test for reducing sugars

Answer 13

Add equal volume of Benedict’s Reagent to a sample
Heat the mixture in an electric water bath at 100 degrees for 5 minutes
Positive results:colour change from blue to orange and brick red precipitate forms

Question 14

Describe the Benedict’s test for non-reducing sugars

Answer 14

Negative results: Benedict’s reagent remains blue

Hydrolyse non reducing sugars e.g. sucrose into their monomers by adding 1CM^3 of HCl. Heat in a boiling water bath for 5 minutes.

Neutralise the mixture using sodium carbonate solution

Proceed with Benedict’s test as usual

Question 15

Describe the test for starch

Answer 15

Add iodine solution

Positive result: colour change from orange to blue-black

Question 16

Outline how colorimetry could be used to give qualitative results for the presence of sugars and starch