Problem 62 - Chemistry: The Central Science

Question

Write a chemical equation for the formation of methionyl glycine from the constituent amino acids.

Step-by-Step Solution

Answer

The chemical equation for the formation of methionyl glycine from methionine and glycine is: \( \textrm{-NH2-CH-(CH2)2-S-CH3-COOH} + \textrm{NH2-CH2-COOH} \rightarrow \textrm{-NH2-CH-(CH2)2-S-CH3-CONH-CH2-COOH} + H_{2}O \) where the peptide bond (-CONH-) is formed between the carboxyl group (-COOH) of methionine and the amino group (-NH2) of glycine, with the release of a water molecule (H2O).

Step 1: Start with the structures of the amino acids

First, we should recall the structures of methionine and glycine, the two amino acids that are involved in this reaction. Methionine consists of an amino group (-NH2), a carboxyl group (-COOH), and the side chain (-CH2-CH2-S-CH3). Glycine, being the simplest amino acid, has an amino group (-NH2), a carboxyl group (-COOH), and a hydrogen atom as its side chain.

Step 2: Consider the peptide bond formation

The process of peptide bond formation involves the carboxyl group (-COOH) of one amino acid reacting with the amino group (-NH2) of another amino acid. This reaction results in the release of a water molecule (H2O) and a peptide bond (-CO-NH-) connecting the two amino acids.

Step 3: Write the equation for methionyl glycine formation

Now, we combine the two amino acids, methionine and glycine, through the peptide bond formation and release a water molecule: \( \textrm{Methionine} + \textrm{Glycine} \rightarrow \textrm{Methionyl Glycine} + H_{2}O \) In terms of their molecular structures, the equation is as follows: \( \textrm{-NH2-CH-(CH2)2-S-CH3-COOH} + \textrm{NH2-CH2-COOH} \rightarrow \textrm{-NH2-CH-(CH2)2-S-CH3-CONH-CH2-COOH} + H_{2}O \) In this equation, the -COOH group of methionine reacts with the -NH2 group of glycine, resulting in the release of a water molecule and the formation of the peptide bond between them, denoted as -CONH-. This reaction produces methionyl glycine.