Which statement best describes what occurs to a molecule of the enzyme trypsin after it binds to a molecule of protein?

Of the following given choices;

A) After binding to a protein molecule, the trypsin molecule is destroyed and must be replaced.

B) The combined trypsin and protein molecule is utilized for energy to power cellular functions.

C) After binding to the protein molecule, trypsin is converted to a lipid and used for energy storage.

D) The trypsin molecule is not chemically altered by the reaction with protein and may be used again.

The answer is; D.

Trypsin is not degraded in the process of breaking down a protein molecule hence continues to break down other proteins. The proteins bind to the active site of the enzyme and the peptide bond is hydrolyzed. The hydrolyzed protein then releases from the active site.  

If a small amount of trypsin is left in a big jar of proteins, over time, the whole proteins will have been hydrolyzed because the enzyme is not degraded in a hydrolysis reaction.