3.1.1/2 Monomers and polymers, Carbohydrates

Question 1

Define monomer
Give examples

Answer 1

Smaller units that join together to form larger molecules
Monosaccharides (glucose, fructose, galactose)
Amino acids
Nucleotides

Question 2

Define polymer
Give examples

Answer 2

Molecules formed when many monomers join together
Polysaccharides
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 the 3 hexose monosaccharides

Answer 5

Glucose
Fructose
Galactose

Question 6

Name the type of bond formed when monosaccharides react

Answer 6

Glycosidic bond

Question 7

Name 3 disaccharides and how they are formed

Answer 7

Maltose - glucose and glucose
Sucrose - glucose and fructose
Lactose - glucose and galactose

Question 8

Draw structure of alpha glucose

Answer 8

google (oh same side)

Question 9

Draw structure of beta glucose

Answer 9

google

Question 10

Describe the structure of starch

Answer 10

Made from amylose - glycosidic bonds, helix with inter molecular H bonds = compact
Amylopectin - glycosidic bonds, branched = many terminal ends for hydrolysis into glucose

Question 11

Functions of starch

Answer 11

Storage polymer of alpha glucose in plant cells
Insoluble - doesn’t damage cells by osmosis
Large - cannot diffuse out of cells

Question 12

Structure and functions of glycogen

Answer 12

Storage polymer of alpha glucose in animals
Glyosidic bonds
Branched - many terminal ends for hydrolysis
Insoluble - no osmotic effect and doesn’t diffuse out
Compact

Question 13

Structure and function of cellulose

Answer 13

Polymer of beta glucose, gives rigidity to plant cell walls
Glycosidic bonds
Straight chain, unbranched molecule
Alternate glucose molecules are rotated 180
H-bond crosslinks between parallel strands form microfibrils = high tensile strength

Question 14

Describe benedict’s test for reducing sugars

Answer 14

Add an equal volume of benedicts reagent to sample
Heat in water bath at 100 for 5 mins
Positive result = colour change from blue to orange and brick red

Question 15

Describe benedicts test for non reducing sugars

Answer 15

Hydrolyse non reducing sugars by adding 1cm^3 HCl, heat in boiling water bath 5 mins
Neutralise mixture using sodium carbonate solution
Proceed with benedicts test as usual

Question 16

Describe the test for starch

Answer 16

Add iodine solution
Positive result = colour change from orange to blue black

Question 17

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

Answer 17

1. Make standard solutions with known concentrations. Record absorbance
2. Plot calibration curve, absorbance on y axis, conc on x axis
3. Record absorbance values of unknown samples. Use calibration curve to read off conc