monomers, polymers and carbohydrates

Question 1

Define monomer

Answer 1

Smaller units that join together to form larger molecules

Question 2

List the common monomers

Answer 2

1. Monosaccharides
2. Amino acids
3. Nucleotides

Question 3

Define polymer

Answer 3

Molecules formed when many monomers join together

Question 4

List the common polymers

Answer 4

1. Polysaccharides
2. Proteins
3. DNA / RNA

Question 5

Describe what occurs in a condensation reaction

Answer 5

• Two molecules are joined together
• A chemical bond is formed
• A water molecule is released

Question 6

Describe what occurs in a hydrolysis reaction

Answer 6

• Two molecules are separated
• Requires the addition of a water molecule
• A chemical bond is broken

Question 7

Name 3 hexose monosaccharides

Answer 7

1. Glucose
2. Fructose
3. Galactose

Question 8

What do hexose monosaccharides have in common

Answer 8

They all have the molecular formula C6H12O6

Question 9

Name the type of bond formed when two monosaccharides react together in a condensation reaction

Answer 9

Glycosidic bond

Question 10

Name the molecule formed from a condensation reaction of 2 monosaccharides

Answer 10

Disaccharide

Question 11

Name the molecule formed from a condensation reaction of many monosaccharides

Answer 11

Polysaccharides

Question 12

Name 3 disaccharides

Answer 12

1. Maltose
2. Sucrose
3. Lactose

Question 13

Explain how maltose is formed

Answer 13

• Via a condensation reaction which releases a water molecule
• Between 2 glucose molecules
• To form a glycosidic bond

Question 14

Describe how sucrose is formed

Answer 14

• Via a condensation reaction which releases a water molecule
• Between a glucose and fructose molecule
• To form a glycosidic bond

Question 15

Describe how lactose is formed

Answer 15

• Via a condensation reaction which releases a water molecule
• Between a glucose and galactose molecule
• To form a glycosidic bond

Question 16

What is the molecular formula for disaccharides of glucose?

Answer 16

C12H22O11

Question 17

Define monosaccharides

Answer 17

The monomers from which larger carbohydrates are made from

Question 18

Define disaccharides

Answer 18

Formed by the condensation of two monosaccharides.

Question 19

What are the structural differences between glucose isomers?

Answer 19

• The OH groups on carbon 1 are inverted
• OH group is below carbon 1 in alpha glucose
• OH group is above carbon 1 in beta glucose

Question 20

Describe the position of the OH group in alpha glucose

Answer 20

Below carbon 1

Question 21

Describe the position of the OH group in beta glucose

Answer 21

Above carbon 1

Question 22

Describe the function of starch

Answer 22

It is an energy storage polymer of alpha glucose in plant cells

Question 23

Explain the structure of starch and explain its benefits

Answer 23

• Made from amylose which forms 1,4 glycosidic bonds and a helix with hydrogen bonds to make it compact
• Made from amylopectin which forms 1,4 and 1,6 glycosidic bonds to make it branched so it has many terminal ends for hydrolysis into glucose

Question 24

How is starch adapted for its function?

Answer 24

1. Insoluble so has no osmotic effect on cells

2. Large molecule so doesn’t diffuse out of cells

Question 25

Describe the function of glycogen

Answer 25

Main energy storage polymer of alpha glucose in animal cells

Question 26

Describe the structure of glycogen

Answer 26

• 1,4 and 1,6 glycosidic bonds so it is branched

Question 27

How is glycogen adapted for its function

Answer 27

1. Branched so has many terminal ends for hydrolysis
2. Insoluble so has no osmotic effect and cannot diffuse out of cells
3. Compact for storage

Question 28

Describe the function of cellulose

Answer 28

A polymer of beta glucose gives rigidity to plant cell walls, prevents bursting under turgor pressure and holds the stem up

Question 29

Describe the structure of cellulose

Answer 29

• 1,4 glycosidic bonds
• Straight chain unbranched molecule
• Alternate glucose molecules are rotated 180
• Hydrogen bonds crosslink between parallel strands to form microfibrils

Question 30

How is cellulose adapted for its function?

Answer 30

1. Microfibrils provide tensile strength to the cell walls
2. Cellulose fibres are permeable which allows water and solutes to leave and each cell surface membrane
3. High tensile strength allows cell walls to be stretched without breaking so they can withstand turgor pressure

Question 31

Describe a method for Benedict’s test for reducing sugars

Answer 31

1. Add an equal volume of Benedict’s reagent to a sample
2. Heat the mixture in a water bath at 100 C for 5 minutes
3. Positive result = colour change from blue to brick red precipitate

Question 32

Describe a method for Benedict’s test for non-reducing sugars

Answer 32

1. Hydrolyse non-reducing sugars into their monomers by adding 1cm^3 of HCl
2. Heat in a boiling water bath for 5 minutes
3. Neutralise mixture using sodium carbonate solution
4. Add Benedict’s reagent to the sample and heat in a boiling water bath again
5. If the colour stays blue = negative, the positive result is an orange/brick red precipitate

Question 33

Describe the test for starch

Answer 33

1. Add iodine dissolved in potassium iodide (KI) solution
2. Shake and stir
3. Positive result = colour change from orange to blue/black

Question 34

How are starch and glycogen formed?

Answer 34

The condensation reaction of alpha glucose

Question 35

How is cellulose formed?

Answer 35

The condensation reaction of beta glucose