Enzymes work best at optimal temperature and pH values. For example, the enzyme, pepsin, in your stomach must be able to function in a highly acidic environment to break peptide bonds found in proteins. Acidic or basic conditions can disrupt the hydrogen bonds between the loops of the protein chains. If this disruption occurs near the active site, the enzyme can become distorted and not fit the substrate perfectly. The rate of reaction is reduced as more enzymes become denatured. Pepsin Lipase Relative Activity 0 2 4 6 8 10
a) What is the optimal pH for pepsin? _ For lipase? _ b) Do you think lipase is an enzyme that is found in the stomach? Why or why not?
The Correct Answer and Explanation is:
)
- The optimal pH for pepsin is pH 2.
- The optimal pH for lipase is pH 8.
b)
No, lipase is not an enzyme that is primarily found in the stomach. It is more active in the small intestine, where the environment is basic (alkaline), not acidic like the stomach.
Explanation
Enzymes are biological catalysts that speed up chemical reactions in the body. Each enzyme has a specific shape, including a region called the active site, where the substrate binds and the reaction takes place. The shape and function of enzymes depend heavily on environmental conditions such as temperature and pH. If the environment becomes too acidic or too basic, the hydrogen bonds and other interactions that maintain the enzyme’s three-dimensional structure can be disrupted. This can lead to denaturation, where the enzyme loses its shape and, as a result, its ability to function effectively.
Pepsin is an enzyme located in the stomach, where it plays a vital role in protein digestion by breaking down peptide bonds. The stomach has a highly acidic environment due to the presence of hydrochloric acid (HCl), resulting in a low pH. Pepsin is uniquely adapted to work best at pH 2, which matches the acidic conditions of the stomach. If the pH rises (becomes less acidic), pepsin’s structure can be altered, reducing its effectiveness.
In contrast, lipase breaks down lipids (fats) and works best at a more basic pH of around 8, which matches the environment of the small intestine, not the stomach. The small intestine receives secretions from the pancreas, including bicarbonate, which neutralizes stomach acid and raises the pH to an alkaline level. Therefore, lipase is most active in the small intestine, not the acidic stomach. If lipase were in the stomach, its activity would be extremely low due to denaturation from the low pH.
Thus, the differences in optimal pH reflect the specific environments where each enzyme functions best in the human digestive system.
