MCAT Organic Question — Reactions | Next Step Test Prep MCAT Organic Question — Reactions | Next Step Test Prep

Fields marked with an * are required

Schedule a Free Tutoring Consultation

A Next Step Academic Manager will contact you within 1 business day or call us now at 888-530-6398.

Contact us

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Save

Consider the following reaction:

Alanine Peptide

Reactions 1 and 2 can be respectively characterized as:

A) peptide bond formation, nucleophilic acyl addition

B) polymerization, hydrolysis

C) hydrolysis, peptide bond formation

D) nucleophilic addition, hydrolysis

 

 

Explanation

 

The reaction depicted shows two alanine molecules forming a peptide bond. The process of combining monomers, such as amino acids, into polymers, such as polypeptides is called polymerization. Reaction 2 shows the reverse reaction with water being used to break a peptide bond. Using water to break a bond can be described as hydrolysis. Thus (B) is the correct answer.

 

A: While reaction 1 is peptide bond formation, the reverse reaction is not an addition reaction. In addition reactions two molecules combine. Here, reaction 2 shows one large molecule being broken down.

 

C: These are the right labels, but applied backwards.

 

D: Reaction 2 is hydrolysis, but reaction 1 is not a nucleophilic addition; it’s a substitution reaction. The OH group is being substituted for the amino group of the amino acid on the right. Thus, this is a nucleophilic acyl substitution.

 

Want more practice?

Fields marked with an * are required

Sign up for our MCAT Question of the Day!

X