Question

An experiment was conducted to measure the reaction rate of the human salivary enzyme -amylase. Ten mL of a concentrated starch solution and 1.0 mL of -amylase solution were placed in a test tube. The test tube was inverted several times to mix the solution and then incubated at 25oC. The amount of product (maltose) present was measured every 10 minutes for an hour. a)Explain why a change in the reaction rate was observed after 30 minutes.

Answer 1

The reaction rate of α-amylase in breaking down starch may decrease after 30 minutes due to a reduction in starch concentration as it is converted to maltose, and possible product inhibition from accumulating maltose.

Step-by-step explanation:

A change in the reaction rate of the human salivary enzyme α-amylase observed after 30 minutes could be due to several reasons. One possibility is that as the enzyme works to break down starch into maltose, the concentration of the substrate (starch) decreases. Over time, this leads to a decrease in the rate of reaction because there is less starch for the enzyme molecules to bind with, reflecting the law of mass action. This drop in substrate concentration aligns with what we understand about enzyme kinetics. Enzymes have a maximum rate that they can catalyze reactions, known as Vmax. Initially, the enzyme works at an optimal rate, but as the substrate concentration falls, the reaction rate also declines until the enzyme becomes saturated. Moreover, the accumulation of the product (maltose) may also inhibit the enzyme, further slowing the reaction rate. This phenomenon, known as product inhibition, occurs because the product competes with the substrate for the active site on the enzyme or alters the enzyme's activity.