Final answer:
Test tube 3 with amylase, cellulose, and pH 7.0 buffer would not show a positive Benedict's test result because cellulose is not a reducing sugar and cannot be broken down by amylase into such sugars.
Step-by-step explanation:
The student asked whether test tube 3, which contains amylase, cellulose, and a pH 7.0 buffer, will show a positive Benedict's test result. Benedict's test is used to identify the presence of reducing sugars, which are sugars that can donate electrons to another chemical. Since amylase breaks down starch, not cellulose, and cellulose is not a reducing sugar, test tube 3 is not expected to show a positive Benedict's test result. Positive results in a Benedict's test are indicated by a color change due to the formation of a precipitate which can vary from green to brick red depending on the concentration of reducing sugar. In the case of cellulose and amylase at a neutral pH, no such reaction would occur because cellulose cannot be hydrolyzed by amylase to produce reducing sugars.