What is the mass of the water molecule released during the formation of a peptide bond?

• A. 17 amu
• B. 18 amu
• C. 32 amu
• D. 44 amu

Answer: (B)

The mass of the water molecule released during the formation of a peptide bond is correctly identified as 18 amu.

To understand why this value is accurate, it's essential to consider the composition of a water molecule, which consists of two hydrogen atoms and one oxygen atom. The atomic masses of these elements are approximately 1 amu for hydrogen and about 16 amu for oxygen. When you sum the mass contributions from the two hydrogen atoms (2 x 1 amu = 2 amu) and the oxygen atom (16 amu), you arrive at a total of 18 amu for the water molecule:

[

2 , \text{amu (H)} + 16 , \text{amu (O)} = 18 , \text{amu (H}_2\text{O)}

]

The context of peptide bond formation involves a condensation reaction, where two amino acids are linked together by a covalent bond while releasing a molecule of water. This dehydration synthesis is a common process in biochemistry, emphasizing the importance of water molecules in biochemical reactions.

Thus, the reduction in mass due to the loss of the water molecule during this process, which is indeed calculated as 18 amu,