Final answer:
The results in tube 1 and tube 2 are the same because both contain a pH 7.0 buffer maintaining the pH needed for amylase to function optimally, regardless of whether the substrate is starch or glucose.
Step-by-step explanation:
The question pertains to the enzyme amylase, which operates optimally at a specific pH, and the buffering capacity of a solution at pH 7.0. The contents of tube 1 (amylase, starch, pH 7.0 buffer) and tube 2 (amylase, glucose, pH 7.0 buffer) lead to the same results because amylase functions well in a pH 7.0, which is close to its optimum pH. Amylase catalyzes the breakdown of starch into sugars like maltose, and since tubes 1 and 2 are buffered to maintain a pH of 7.0, the enzyme retains its activity. In tube 2, glucose is already a simple sugar and does not need to be broken down by amylase, but it still shows the stability of the enzyme activity in the given pH buffer.
Buffers maintain a consistent pH by adjusting the ratio of acid and conjugate base in the solution. As such, the pH stability stems from the buffer's capacity to resist changes in pH despite potential addition of acids or bases. This attributes to the unchanged pH when adding different amounts or types of substances, as long as the buffer capacity is not surpassed. Therefore, the pH remains constant in both tubes due to the effective buffer system in place.