Question

Which of the following describes the effect of boiling and freezing? which of the following describes the effect of boiling and freezing? boiling and freezing both denatured amylase. boiling denatured the enzyme, but freezing had no effect. freezing denatured the enzyme, but boiling had no effect. boiling and freezing had no effect on amylase?

Answer 1

Boiling denatures the enzyme, but freezing has no effect.

At high temperatures (even if it’s not boiling, about 60°C is enough) hydrogen bonds and other interactions between different amino acids of an enzyme are broken. This is not degradation, no bonds are broken – only interactions (London, Van der Waals, etc). This makes the protein to denature, which means it will lose its 3D shape and become linear – no longer globular: it only preserves its primary structure. This makes the enzyme to become useless: it can’t make the substrate become product anymore. So the activity becomes practically zero.

Freezing DOES make a change in enzyme activity, but for other reasons which are not denaturing (the enzyme has the same structure as before):

-Concentration: Now some of the water has become ice and you have 2 phases, which are the solution and the ice. So the solution has less water, and so a higher concentration. Higher concentration means… higher activity! So it has the same structure, but it works more.

-Cell disruption: Membranes are broken and this will release molecules that used to be stored in an organelle. Sometimes this makes the enzyme find the substrate – so it actually increases activity! As I said for concentration, this means the enzyme has the same structure but it works more.