Question

β-Galactosidase (β-gal) is a hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. A 0.312 gram sample of β-galactosidase is dissolved in water to make 0.108 L of solution, and the osmotic pressure of the solution at 25 °C is found to be 0.615 mbar. Calculate the molecular mass of β-galactosidase.

Answer 1

Osmotic pressure is proportional to molarity (M) of the solution at a given temperature ‘T’. Osmotic pressure can be calculated by the following relationship:

π = MRT

Where ‘π’ is the osmotic pressure, ‘M’ is the mass of beta-galactosidase in this case, ‘R’ the gas constant = 0.08314 Lbar/molK and 'T’ the temperature in Kelvin.

Here π = 6.1510^-4 bar, R = 0.08314 Lbar/molK and T = (273+25) K = 298 K

By substituting the values in the above equation,

6.1510^-4 bar = M0.08314 Lbar/molK X 298 K

M = 2.48210^-5 mol/L

2.48210^-5 mol is present in 1L. Therefore, in 0.108L, it becomes:

2.48210^-5 mol/L 0.108L = 2.6810^-6 mol

0.312g2.6810^-6 mol = 11641.8 g/mol = 1.1610⁵ g/mol

Hence the molecular mass of β-galactosidase is 1.1610⁵ g/mol.