Question

Silver ions are known to react with the sulfhydryl groups of proteins and therefore and inhibit the action of certain enzymes. In one reaction, 0.0075 g of AgNO3 is needed to completely inactivate a 5-mL enzyme solution. Estimate the molar mass of the enzyme. Explain why the molar mass obtained represents the minimum value. The concentration of the enzyme solution is such that 1 mL of the solution contains 75 mg of the enzyme. Assume there is a 1:1 binding between silver ions and the protein.

Answer 1

Mass of silver nitrate is 0.0075 g.

Molar mass of silver nitrate is 169.9 g/mol.

The number of moles of silver nitrate is

Number of moles of silver ions = number of moles of silver nitrate = number of moles of protein

(because there is a 1:1 binding between silver ions and the protein).

Volume of enzyme solution is 5 mL.

1 mL of solution contains 75 mg of enzyme

5 mL of solution will contain enzyme.

Minimum molar mass of the enzyme

This is minimum molar mass as we have assumed 1:1 binding between silver ions and the protein. There can be 2:1 binding between silver ions and the protein or there can be 3:1 binding between silver ions and the protein.In such cases, the number of moles of protein will be less and the molar mass will be higher.