Question

when an apple is cut, oxygen comes in contact with the fruits inner tissue and browning occurs. one particular enzyme in the apple cells, polyphenol oxidase, begins breaking down the tissue. people will often squeeze lemon juice over their apple slices to prevent them from turning brown. how does this affect the activity of the enzyme? (hint: lemon juice is acidic and has a ph of 2)

Explanation:

Enzymes have an optimal pH for activity. Polyphenol oxidase in apples works best in a certain pH range. Lemon - juice being acidic (pH 2) changes the pH around the apple tissue. This acidic environment is not the optimal pH for polyphenol oxidase, causing its activity to decrease or become inhibited.

Answer:

The acidic lemon juice lowers the pH around the apple tissue, inhibiting the activity of the polyphenol oxidase enzyme, thus preventing browning.