Question

The enzyme, carbonic anhydrase, is a large zinc-containing protein with a molar mass of 3.00 x10^4 g/mol. Zn is 0.218% by mass of the protein. How many zinc atoms does each carbonic anhydrase molecule contain

Answer 1

The mathematical expression for mass percent is given by:

$Mass percent = \frac{mass of the compound}{molar mass of the compound}\times 100$

Put the values,

$0.218 percent of zinc = \frac{mass of zinc}{3.00 \times 10^{4} g/mol}\times 100$

mass of zinc = $0.218 \times (3\times 100) g$

= $0.654 \times 100 g$ or 65.4 g

Now, number of moles of zinc  =$\frac{given mass in g}{molar mass of zinc}$

= $\frac{65.4 g}{65.38 g/mol}$

= 1.00 mole

Number of atoms of zinc is calculated by the Avogadro number.

Now, according to mole concept

$6.022\times 10^{23}$ molecules of enzyme consists of $6.022\times 10^{23}$ atoms of zinc

So, 1 molecule of enzyme contains  =$\frac{6.022\times 10^{23}atoms of zinc}{6.022\times 10^{23} }$

= 1 atom of zinc.

Hence, every carbonic anhydrase molecule consists of 1 atom of zinc.