Chemistry - Rings, Polymers and Analysis - F324 - Polymers and Synthesis (2)

Question 1

What is a peptide?

Answer 1

A peptide is a compound made of amino acids linked by peptide bonds.

Question 2

How many amino acids are found in the human body?

Answer 2

20 different amino acids are found in the body.

Question 3

Are amino acids soluble in acids or bases?

Answer 3

Amino acids are soluble in both acids and bases.

Question 4

Define a zwitterion.

Answer 4

A zwitterion is a dipolar ionic form of an amino acid that is formed by the donation of a hydrogen ion from the carboxyl group to the amino group. Because both charges are present, there is no overall charge.

Question 5

Define the isoelectric point.

Answer 5

The isoelectric point is the pH value at which the amino acid exists as a zwitterion.

Question 6

If the amino acid is put at a pH that is more acid than its isoelectric point, what will happen?

Answer 6

If the pH is more acid than the amino acids isoelectric point then the amino acid behaves as a base and accepts a proton to form a positively charged ion.

Question 7

If the amino acid is put at a pH that is more alkaline than its isoelectric point, what will happen?

Answer 7

If the pH is more alkaline than the amino acids isoelectric point then the amino acid will behave as an acid and donate a proton to form a negatively charged ion.

Question 8

Proteins are long polypeptides of how many amino acids?

Answer 8

Proteins are polypeptides of more than 50 amino acids.

Question 9

What is the result of acid hydrolysis of polypeptides and proteins?

Answer 9

During acid hydrolysis, the amino acids formed are positively charged because of the presence of H+ ions from the acid.

Question 10

What conditions are used for the acid hydrolysis of polypeptides/proteins?

Answer 10

Traditionally the protein/polypeptide is heated under reflux with 6 moldm-3 HCl for 24 hours.

Question 11

What conditions are used for the alkaline hydrolysis of proteins/polypeptides?

Answer 11

A solution of alkali in the form of aqueous sodium hydroxide is used at just above 100oC.

Question 12

What is the result of alkaline hydrolysis of proteins/polypeptides?

Answer 12

Broken down into amino acids in the form of their sodium salts.

Question 13

Define a stereoisomer.

Answer 13

Stereoisomers are species with the same structural formula but with a different arrangement of the atoms in space.

Question 14

Define optical isomers.

Answer 14

Optical isomers (or enantiomers) are stereoisomers that are non-superimposable mirror images of each other.

Question 15

In what type of molecules do optical isomers arise?

Answer 15

Optical isomers arise in organic molecules that contain a carbon atom attached to four different atoms.

Question 16

What is a chiral carbon?

Answer 16

A chiral carbon is a carbon atom attached to four different atoms or groups of atoms.

Question 17

A mixture of equal amounts of each optical isomer is called what?

Answer 17

A mixture of equal amounts of each optical isomer is called a racemic mixture.

Question 18

What does condensation polymerisation require?

Answer 18

Condensation polymerisation requires monomers with two different functional groups.

Question 19

What functional groups are needed in the monomers to make a polyester?

Answer 19

The hydroxyl and the carboxyl functional groups.

Question 20

What functional groups are needed in the monomers to make a polyamide?

Answer 20

The carboxyl and the amine functional groups.

Question 21

Addition polymers are made from how many types of monomer?

Answer 21

Addition polymers are made from one type of monomer.

Question 22

If the monomer contains a double bond, then what type of polymerisation will occur?

Answer 22

If the monomer contains a double bond then addition polymerisation will occur.

Question 23

What is the result of alkaline hydrolysis of polyesters?

Answer 23

Alkaline hydrolysis of polyesters results in each ester linkage being hydrolysed to the sodium salt of the carboxylic acid.

Question 24

What is the result of acid hydrolysis of esters?

Answer 24

The monomer units of the polyester are produced.

Question 25

When polyamides are hydrolysed in acid conditions, what is the result?

Answer 25

When polyamides are hydrolysed in acid conditions, the dicarboxylix acid is produced together with an ammonium salt of the diamine.

Question 26

When polyamides are hydrolysed in basic conditions, what is the result?

Answer 26

When polyamides are hydrolysed in basic conditions, the sodium salt of the dicarboxylic acid and the diamine are formed.

Question 27

What is a biodegradable polymer?

Answer 27

A biodegradable polymer is a polymer that breaks down completely into carbon dioxide and water.

Question 28

What is a degradable polymer?

Answer 28

A degradable polymer is a polymer that breaks down into smaller fragments when exposed to light or heat or moisture.

Question 29

What is/was seldane used for?

Answer 29

Seldane was one of the first antihistamines.

Question 30

What did the other optical isomer in Seldane do?

Answer 30

The other optical isomer caused a potentially fatal heat condition in some patients.

Question 31

What are the benefits of producing a single isomer with the correct pharmacological activity?

Answer 31

The risks from undesirable side effects are reduced and the drug doses may also be reduced.

Question 32

Why is separation of two optical isomers difficult?

Answer 32

Separation is difficult because optical isomers usually have the same or similar physical properties - melting points, boiling points and solubilities.

Question 33

What separation techniques tend to be used to separate optical isomers?

Answer 33

Separation techniques include the use of enzymes, electrophoresis and chromatography.