Final answer:
The question relates to the enzymatic activity of peptidase on starch at a neutral pH of 7.0, where peptidase is not expected to digest starch since it targets proteins, not carbohydrates. The expected outcome is no significant digestion of starch by peptidase in tube 5.
Step-by-step explanation:
The Nature of Enzyme Activity in Biochemical Reactions
The question pertains to the activity of the enzyme peptidase on starch in an environment with a pH of 7.0. Peptidases are a group of enzymes that break down proteins into smaller peptides or amino acids. The experiment described likely aims to investigate if the enzyme can act on starch at neutral pH. However, considering that peptidases do not target starch, which is a carbohydrate, and instead act on proteins, the expected result would be that there is no significant digestion of starch occurring in tube 5. This is because the presence of peptidase would not catalyze the breakdown of starch, a polysaccharide. Alternatively, the optimum pH for enzyme activity is an important factor to consider in these types of biochemical experiments, as different enzymes have different optimal pH levels for their activity.
For example, digestive enzymes such as salivary amylase have an optimum pH near neutrality (approximately pH 7.0) and are meant to function in the digestion of carbohydrates like starch. Pepsin, a type of proteolytic enzyme, functions optimally in the highly acidic environment of the stomach (pH 1.5 - 2.5), targeting protein digestion, not carbohydrates. Therefore, the combination of peptidase with starch at a neutral pH suggests either the purpose is to confirm the specificity of peptidase activity (i.e., it does not break down starch) or it is an incorrectly designed experiment lacking the appropriate enzyme, such as amylase, which would be capable of starch digestion at this pH.