Question

Before the equivalence point:

The protein apotransferrin binds two Fe(lll) ions for cell transport. Consider when a 1.00 mL solution of apotransferrin is titrated with 102 muL. of a 1.72 M Fe(lll) solution. The initially colorless solution turns red, and the color change can be measured with a spectrophotometer. First, explain why there is a difference in spectrophotometric response during titration before and after the equivalence point by placing the statements below into the appropriate categories. Before the equivalence point After the equivalence point Now, calculate the concentration of apotransferrin present in the original 1.00 mL solution.

After the equvalence point:

Now, calculate the concentration of apotransferrin present in the original 1.00 mL solution. ________ M Apotransferrin

Answer 1

Before the equivalence point, the color change is drastic as All Fe(III) added will bind to the protein.

After the equivalence point, the color change is minimal as no binding sites are available for Fe(III).

Now, calculate the concentration of apotransferrin present in the original 1.00 mL solution.

Here and are the molar concentration and volume of apotransferrin and and are the molar concentration and volume of Fe(IIII) solution. Also, each apotransferrin protein accepts two Fe(III) ions.

Hence,

Hence, the concentration of apotransferrin present in the original 1.00 mL solution is

0.0875 M Apotransferrin.