1. Biuret reagent and sodium hydroxide are added to a 2 mL sample of an unknown solution. After some time, the sample displays a light blue color (the same as the original reagent). In terms of macromolecules, what do these results indicate?

Starch was present in unknown solution

Explanation:

Given in the question that when sodium hydroxide and a reagent is added to an unknown solution, the solution shows blue colour.

This events indicate that the reaction performed was the Iodine Test, which is used to detect the presence of starch.

The reagent was Iodine solution which added in presence of NaOH to increase the pH and prevent the dissociation of starch which was present in the unknown solution. The final solution turned blue because the colour of Starch-Iodine complex is blue.