Final answer:
Tube 2 and Tube 3 show the same amount of digested starch because amylase, which digests starch, performs optimally at pH 7.0, the condition maintained in both tubes.
Step-by-step explanation:
If Tube 2 (amylase, starch, pH 7.0 buffer) appears to have the same amount of starch digested as Tube 3 (amylase, starch, pH 7.0 buffer), the most likely explanation is that amylase works optimally at pH 7.0. Amylase is an enzyme that digests starch, and both tubes contain a pH 7.0 buffer, which helps maintain the optimal pH for amylase activity. The fact that both tubes show the same amount of starch digested suggests that the digestion of starch is indeed pH-dependent and that the enzyme amylase has a specific range in which it operates most effectively. Digestive enzymes like pancreatic amylase exhibit optimal activity at or near the physiological pH of 7.4, but the exact optimum can vary slightly, such as pH 7.1 for pancreatic amylase. Amylase breaks the chain of starches at specific points, making it crucial for proper digestion.