THE ACTIVITY OF PTYALIN IS LIKELY TO DECREASE WITH AN INCREASE IN THE CONCENTRATION OF

• A. oxygen
• B. starch
• C. protein
• D. acid ✓

The answer to the question is: D. acid

The activity of ptyalin, an enzyme found in saliva that helps break down starches into simpler sugars, is likely to decrease with an increase in the concentration of acid. Ptyalin functions optimally in a slightly alkaline environment, and an increase in acid concentration would lead to a more acidic environment, thus inhibiting the activity of ptyalin.

When the pH level becomes more acidic, the enzyme’s activity decreases as it denatures under acidic conditions. This denaturation results in a loss of the enzyme’s catalytic function, leading to a decrease in its ability to break down starches effectively. Therefore, an increase in acid concentration would hinder the activity of ptyalin.