Pepsin, a common enzyme found in the stomach, is most active at pH values between 0.5 and 2.5. It works slowly between pH values
of 2.6 and 3.4. Beyond a pH of about 3.5, it becomes completely inactive. Why does this happen? a. The change in pH affects the shape and function of the enzyme. It can only function properly in its optimal pH range.
b. The enzyme inactivates because it melts into a liquid when it is not at the right pH.
c. Because a pH of 3.5 is an acid and eats away at the enzyme.
d. pH changes also affect temperature, and that affects the reaction.
The correct answer is A. the change in pH affects the shape and function of the enzyme. It can only function properly in its optimal pH range. Enzymes are protein molecules and they have a specific shape, which is altered by temperatures and pH that are not within the enzyme's range of operation. This is because the temperature and pH alter the enzyme's structure, which means the shape of its active site is changed and its substrate is not able to fit inside the active site of the enzyme molecule.
Sample Response: The first stage of cellular respiration occurs in the cytoplasm. This is where glucose is broken down into smaller molecules. A small amount of energy is also released. The second stage occurs in the mitochondrion. This is where the small molecules combine with oxygen to produce water, carbon dioxide, and a large amount of energy.
