MDCAT Chemistry MCQ #4875

An unknown amino acid has a molecular mass of 117 amu. If the general backbone (H2N-CH-COOH) mass is 74 amu, what is the mass of the R-group?

MDCAT Chemistry MCQ #4875

  1. Question 1

    Q1. An unknown amino acid has a molecular mass of 117 amu. If the general backbone (H2N-CH-COOH) mass is 74 amu, what is the mass of the R-group?

    • A) 15 amu
    • B) 75 amu
    • C) 43 amu
    • D) 57 amu

    Answer: 43 amu

    Explanation: The mass of the R-group is Total Mass (117) minus the constant amino acid backbone mass (74). Option B incorrectly subtracts only the glycine residue.