A student wants to know what macromolecules are in a piece of bread. To do this, she crushes up the bread using a mortar and pestle and places it in a test tube. Next, she adds Biuret's reagent to test for the presence of one specific macromolecule. The resulting solution turned purple. What does this tell the student?

Question

HINT: Purple > Positive > Protein
Responses

There are carbohydrates in the bread because the result was positive for carbohydrates.
There are carbohydrates in the bread because the result was positive for carbohydrates.

There are proteins in bread because the result is positive for proteins.
There are proteins in bread because the result is positive for proteins.

There are not proteins in the bread because the result was negative for proteins.
There are not proteins in the bread because the result was negative for proteins.

There are not carbohydrates in the bread because the result was negative for carbohydrates.

Answer 1

The correct response is:

There are proteins in bread because the result is positive for proteins.

The purple color change after adding Biuret's reagent indicates the presence of proteins in the bread, as Biuret's reagent specifically tests for peptide bonds found in proteins.