Photo AI
In response to a pain stimulus, the brain produces small polypeptide molecules called enkephalins - VCE - SSCE Chemistry - Question 16 - 2009 - Paper 1
Question 16
In response to a pain stimulus, the brain produces small polypeptide molecules called enkephalins. These molecules block the transmission of pain through the central... show full transcript
Worked Solution & Example Answer:In response to a pain stimulus, the brain produces small polypeptide molecules called enkephalins - VCE - SSCE Chemistry - Question 16 - 2009 - Paper 1
Step 1
Identify the functional groups
Answer
To solve this problem, we need to identify the number of each functional group present in the polypeptide methionine enkephalin, which consists of the amino acid sequence Tyr – Gly – Gly – Phe – Met.
- Amine Group (–NH₂): The first amino acid, Tyrosine (Tyr), contains one amine group at the beginning of the chain; thus, there is 1 amine group.
- Carboxylic Acid Group (–COOH): Each amino acid has a carboxyl group. Since there are 5 amino acids (Tyr, Gly, Gly, Phe, Met), there are 5 carboxylic acid groups in total.
- Amide Group (–CONH): In this case, the connection between the amino acids involves amide (peptide) bonds. There is one amide bond for each peptide link minus one for the terminal amino acid at the end. Therefore, with 5 amino acids, there are 4 amide groups.
Step 2