1.1 Monomers, Polymers & 1.2 Carbohydrates

Question 1

Define monomer.

Answer 1

Smaller units that join together to form larger molecules.

Question 2

Give 3 examples of monomers.

Answer 2

Monosaccharides (glucose, fructose, galactose), amino acids, nucleotides.

Question 3

Define polymer.

Answer 3

Molecules formed when many monomers join together.

Question 4

Give 3 examples of polymers.

Answer 4

Polysaccharides, proteins, DNA/RNA

Question 5

What happens in a condensation reaction.

Answer 5

A chemical bond forms between 2 molecules & a molecule of water is produced.

Question 6

What happens in a hydrolysis reaction.

Answer 6

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

Question 7

Name 3 hexose monosaccharides.

Answer 7

Glucose, fructose, galactose; all have the molecular formula C6H12O6.

Question 8

What type of bond is formed when monosaccharides react?

Answer 8

(1,4 or 1,6) glycosidic bond.

Question 9

Describe how disaccharides form.

Answer 9

Condensation reaction forms a glycosidic bond between 2 monosaccharides.

Question 10

Name 3 examples of disaccharides.

Answer 10

1. Maltose: glucose + glucose
2. Sucrose: glucose + fructose
3. Lactose: glucose + galactose
   All have molecular formula C12H22O11

Question 11

What is starch?

Answer 11

A storage polymer of α-glucose in plant cells.

Question 12

Why is starch insoluble?

Answer 12

It has no osmotic effect on cells.

Question 13

Why is starch large?

Answer 13

It does not diffuse out of cells.

Question 14

What are the components of starch?

Answer 14

Amylose and amylopectin.

Question 15

What type of bonds are found in amylose?

Answer 15

1,4 glycosidic bonds.

Question 16

What is the structure of amylose?

Answer 16

A helix with intermolecular hydrogen bonds, making it compact.

Question 17

What type of bonds are found in amylopectin?

Answer 17

1,4 and 1,6 glycosidic bonds.

Question 18

What is the structure of amylopectin?

Answer 18

Branched with many terminal ends for hydrolysis into glucose.

Question 19

What is the main storage polymer of α-glucose in animal cells?

Answer 19

Glycogen

Question 20

What types of glycosidic bonds are present in glycogen?

Answer 20

1,4 & 1,6 glycosidic bonds

Question 21

Why is glycogen branched?

Answer 21

To provide many terminal ends for hydrolysis.

Question 22

Why is glycogen considered insoluble?

Answer 22

It has no osmotic effect and does not diffuse out of cells.

Question 23

What is a characteristic of glycogen’s structure?

Answer 23

It is compact.

Question 24

What type of glucose is cellulose a polymer of?

Answer 24

β-glucose

Question 25

What is the primary function of cellulose in plant cell walls?

Answer 25

Gives rigidity and prevents bursting under turgor pressure

Question 26

What type of bonds are present in cellulose?

Answer 26

1,4 glycosidic bonds

Question 27

What is the structure of cellulose in terms of molecular shape?

Answer 27

Straight-chain unbranched molecule

Question 28

How are alternate glucose molecules arranged in cellulose?

Answer 28

They are rotated 180°

Question 29

What forms microfibrils in cellulose?

Answer 29

Hydrogen bond crosslinks between parallel strands

Question 30

What property does cellulose provide due to its structure?

Answer 30

High tensile strength

Question 31

What is the first step in Benedict's Test for reducing sugars?

Answer 31

Add an equal volume of Benedict's reagent to a sample.

Question 32

What temperature and duration should the mixture be heated in Benedict's Test?

Answer 32

Heat the mixture in an electric water bath at 100℃ for 5 mins.

Question 33

What indicates a positive result in Benedict's Test for reducing sugars?

Answer 33

Colour change from blue to orange & brick-red precipitate forms.

Question 34

What is a negative result in Benedict's Test for non-reducing sugars?

Answer 34

Benedict's reagent remains blue.

Question 35

How do you hydrolyse non-reducing sugars like sucrose?

Answer 35

Add 1cm3 of HCl and heat in a boiling water bath for 5 minutes.

Question 36

What should you do after hydrolysing non-reducing sugars?

Answer 36

Neutralise the mixture using sodium carbonate solution.

Question 37

What is the next step after neutralising the mixture in Benedict's Test?

Answer 37

Proceed with the Benedict's test as usual.

Question 38

Test for Starch

Answer 38

1. Add iodine solution. 2. Positive result: colour change from orange to blue-black.

Question 39

How colourimetry could be used to give qualitative results for the presence of sugars and starch.

Answer 39

1. Make standard solutions with known concentrations. Record absorbance or % transmission values. 2. Plot calibration curve: absorbance or % transmission (y-axis), concentration (x-axis). 3. Record absorbance or % transmission values of unknown samples. Use a calibration curve to read off the concentration.

Question 40

Structure of a-glucose

Answer 40

H above OH

Question 41

Structure of beta-glucose

Answer 41

OH above H