Topic 3: Nucleophilic Acyl Substitution and Peptides

In nucleophilic acyl substitution, which of the following is considered the best leaving group?

Which of the following is a common intermediate in nucleophilic acyl substitution reactions?

• Carbocation

• Carbanion

• Tetrahedral intermediate

• Radical

In non-ribosomal peptide synthesis, which enzyme is primarily responsible for the activation of amino acids?

• Peptidyl transferase

• Aminoacyl-tRNA synthetase

• Adenylation domain

• Ribosome

What is the role of the peptidyl carrier protein domain in non-ribosomal peptide synthesis?

• To activate amino acids

• To transfer the growing peptide chain

• To catalyse peptide bond formation

• To release the final peptide product

Which of the following is NOT a characteristic of non-ribosomal peptide synthesis?

• Template-driven synthesis

• Use of modular enzyme complexes

• Incorporation of non-proteinogenic amino acids

• Independent of mRNA

In non-ribosomal peptide synthesis, which domain is responsible for the cyclisation of the peptide?

• Epimerisation domain

• Condensation domain

• Cyclisation domain

• Thioesterase domain

Which of the following best describes the selectivity of non-ribosomal peptide synthetases?

• They are highly selective for ribosomal amino acids only.

• They can incorporate a wide variety of substrates, including non-standard amino acids.

• They only synthesise peptides with even numbers of amino acids.

• They are selective for nucleic acids.

Draw the product of the following reaction where the gamma phosphate is the reacting electrophilic center:

Amide bond forms from the reaction of…

• Esters and ammonia

• Carboxylic acid and excess ammonia

• Esters and excess ammonia

• Carboxylic acid and ammonia

• None of these

What is the property of the species labeled Cl?

• Nucleophile

• Electrophile

• Zwitterionic

• Leaving group

• Protecting group