Question

The percentage of Se in peroxidase enzyme is 0.5% by mass (atomic mass of Se = 78.4 amu). Then, the minimum molecular mass of enzyme which contains not more than one Se atom is:

• A. $1.568\times {10}^{4}amu$
• B. $1.568\times {10}^{7}amu$
• C. $1.568\times {10}^{3}amu$
• D. $1.568\times {10}^{6}amu$

Answer 1

The correct option is A $1.568\times {10}^{4}amu$

We are given that the enzyme contains one atom of selenium. Therefore the mass of the enzyme containing only one atom of selenium corresponds to the minimum molecular mass of the enzyme. Let the molecular mass of the enzyme be y amu. Therefore

[ Total mass of selenium / Molecular mass of the enzyme ] X 100 = 0.5 %

We are given that the atomic mass of selenium is 78.4 amu. Therefore, we will have

( 78.4 / y) X 100 = 0.5

This gives us y = 15680 amu

Therefore the minimum molecular mass of the enzyme is 15680 amu.