Final answer:
The molecular weight of ala-ala, a dipeptide consisting of two alanine molecules, is 160 daltons after accounting for the water molecule lost during peptide bond formation.
Step-by-step explanation:
The question asks about the molecular weight of a dipeptide made up of two alanine molecules, referred to as ala-ala. When alanine (with a molecular weight of 89 daltons) forms a dipeptide, one water molecule (18 daltons) is removed during the peptide bond formation. Therefore, the molecular weight of ala-ala is calculated as twice the molecular weight of alanine minus the weight of the water molecule lost during the condensation reaction.
Molecular weight of alanine: 89 daltons
Molecular weight of water: 18 daltons
Molecular weight of ala-ala: (2 × 89 daltons) - 18 daltons = 178 - 18 = 160 daltons.
So the correct answer is not listed in the given options, and it should be 160 daltons.