Final answer:
Hydrochloric acid was used to stop the enzymic reaction because it acts as an enzyme inhibitor.After 8 minutes of incubation in the dark, the reagent used to stop the reaction was Acetic acid, due to its ability to denature enzymes by altering the pH levels.
Step-by-step explanation:
The students used Hydrochloric acid (HCl) to stop the enzymic reaction. Hydrochloric acid was successful in stopping the enzymic reaction because it acts as an enzyme inhibitor. Enzyme inhibitors can bind to enzymes, either reversibly or irreversibly, and prevent them from carrying out their normal catalytic function. Hydrochloric acid, in this case, most likely irreversibly inhibits the HRP enzyme, leading to the stoppage of the reaction.
During the last lab, students used HRP enzyme to catalyze the reaction between o-phenylenediamine and H2O2. After 8 minutes of incubation in the dark, the reagent used to stop the reaction was Acetic acid; the reason for its effectiveness lies in the denaturation of enzymes. Denaturation occurs because enzymes, which are proteins, can lose their native structure due to the introduction of a substance that changes the pH levels or increases the temperature beyond an enzyme's optimal range, causing it to become inactive. In this case, acetic acid successfully stops the enzymatic reaction by changing the pH, leading to the denaturation of the HRP enzyme.