Enzymes and Energy
In general, enzymes are protein molecules which must be folded in a specific three-dimensional shape in order to function properly. Certain environmental parameters can affect enzyme activity, including pH and temperature. If an enzyme’s shape changes significantly and it can no longer function, the enzyme is said to have become denatured.
The enzyme pancreatic amylase is manufactured and secreted by the pancreas into the duodenum (the large, beginning portion of the small intestine). Pancreatic amylase breaks down starch into maltose, a disaccharide. Pepsin is an enzyme that is released by the epithelium of the stomach, and functions in the stomach to break down proteins into smaller polypeptide units.
The following graphs show the activities of various enzymes under various environmental conditions.
At what temperature would enzyme B be completely denatured?
Denaturation implies that the enzyme has lost all function because its shape has significantly changed. According to the graph, enzyme B has no activity below 170 C or above 430 C. Therefore, choice A is incorrect because this is the optimal temperature. Both choices B and C are out of the activity range, but cold temperatures do not cause denaturation, they simply cause a slowing of the reaction rate based on general kinetic principles until it is ultimately zero. Only high temperatures will cause denaturation, so choice D (500 C) must be correct.