2 - Polypeptides and Proteins

Question 1

What type of reaction produces a dipeptide?

Answer 1

A condensation reaction produces a dipeptide.

Question 2

What’s eliminated in a dipeptide reaction?

Answer 2

A water molecule is eliminated.

Question 3

How can you form an isomer of the dipeptide?

Answer 3

You can form a different dipeptide (isomer) from the amino acids by arranging them in another order. You can change the first amino acid and so the carboxylic acid of an amino acid may react differently with another amino acid.

Question 4

What are the two ways polypeptides can be hydrolysed?

Answer 4

Acid/Alkaline hydrolysis.

Question 5

What happens in Acid Hydrolysis?

Answer 5

Hot aqueous ace is used. A water molecule is needed to break each peptide link to form the constituent amino acids. The amino acids that are formed are positively charged because of the H+ ions from the acid. This is done with 6 mol dm-3 HCl for 24 hours.

Question 6

What happens in Alkaline Hydrolysis?

Answer 6

A solution of NaOH just above 100 C is used. The polypeptide is broken down into amino acids in the form of their sodium salts.