3.3.12-13 Polymers, DNA, proteins and amino acids

Question 1

How do you produce a polyester?

Answer 1

1. Dicarboxylic acid + diol (ester bond)
2. Hydroxycarboxylic acids

Question 2

What monomers is Terylene made from?

Answer 2

Ethane-1,2-diol
Benzene-1,4-dicarboxylic acid

Question 3

How do you produce polyamides?

Answer 3

Diamine + dicarboxylic acids

Question 4

What monomers is Nylon-6,6 made from?

Answer 4

1,6-diaminohexane
1,6-hexanedioic acid

Question 5

What monomers is Kevlar made from?

Answer 5

1,4-benzenediamine
1,4-benzenedicarboxylic acid

Question 6

Why does Kevlar have a high melting point ?

Answer 6

• Chains are straighter, lie closer together
• Hydrogen bonds form between the N-H polar bonds and lone pair on the C=O in the amide bonds

Question 7

What is the use of polyesters like Terylene?

Answer 7

• Thermoplastic that can form fine fibres
• Use in artificial fabrics
• Moulded into plastic bottles and containers

Question 8

What is the use of the artificial polyamide Nylon-6,6?

Answer 8

• Cheap substitute for silk
• Use in ropes, velcro, clothing and carpets

Question 9

What is the use of the aromatic polyamide Kevlar?

Answer 9

• Tough and lightweight
• Bulletproof vests

Question 10

Why are polyesters and polyamides preferred over polyalkenes?

Answer 10

• Polyesters/amides are more easily broken down in landfill sites using hydrolysis reactions
• Hydrolyse the ester/amide bond
• Polyalkenes are inert due to the C-C bond between the monomers

Question 11

What three ways can polymers be disposed of?

Answer 11

Landfill
Incineration
Recycling

Question 12

What are the advantages and disadvantages of landfill?

Answer 12

+ve = biodegradable polymers slowly degrade

-ve = limited land available, leaching of toxic compounds, gas emissions (methane)

Question 13

What are the advantages and disadvantages of incineration?

Answer 13

+ve = energy released for generating electricity, less space than landfill

-ve = CO2 gas emissions, toxic gas emissions

Question 14

What are the advantages and disadvantages of recycling?

Answer 14

+ve = reuse and conservation of hydrocarbon resources, less waste to landfills

-ve = time consuming, expensive, requires energy for collection/sorting/seperating/remoulding

Question 15

What bond forms between amino acids and how?

Answer 15

Amide bond
Condensation reaction

Question 16

What happens to amino acids in acidic/alkaline conditions?

Answer 16

Acidic = Gain proton at -NH2

Alkaline = Lose proton at -OH

Question 17

What are amino acids said to be because of their basic/acidic properties?

Answer 17

Amphoteric

Question 18

What is a zwitterion?
Where does it occur?

Answer 18

• Amino acid with both a positive NH3+ and a negative COO-
• A solution of amino acid in water will exist as zwitterons (acting as a buffer)

Question 19

What is it called when the zwitterion is neutral (neither negative/positive is dominating)?

Answer 19

Isoelectric point of the amino acid

Question 20

What bonds are found in the tertiary structure of a protein?
What do they occur between?

Answer 20

Occur between the R groups of amino acids:
- Hydrogen bonds
- Ionic bonds
- Disulfide bridges
- Hydrophobic interactions

Question 21

How do you hydrolyse an amide bond?

Answer 21

• Concentrated HCl and heat
• Enzymes

Question 22

Why can only certain stereoisomers of a drug be useful in treating a disease?

Answer 22

Receptor sites for drug are stereoselective, active site of enzyme only has complimentary shape to the correct isomer.

Question 23

What are the two ends of a DNA molecule that are recognised by an enzyme?

Answer 23

3’ (OH- on bottom deoxyribose sugar)
5’ (carbon on top phosphate)

Question 24

How many hydrogen bonds form between each of the base pairs in DNA?

Answer 24

C≡G
A=T

Question 25

What happens to cis-platin as it enters the body?

Answer 25

• Passes through cell surface membrane, Cl- ligands are substituted by water ligands
• Water ligands removed so that cis-platin can from dative covalent bonds with the adenine or guanine bases in DNA
• Stops cells from replicating and dividing