Biological molecules：练习题

Which chemical element is found in all proteins but is not usually found in carbohydrates or fats?

A student uses Biuret reagent to test a food sample. The color of the solution changes from blue to purple. Which biological molecule is present in the sample?

Which set of reagents would be required to show that a food sample contains both protein and reducing sugar?

A student tests a liquid food sample by adding Benedict's solution and heating the mixture in a water bath. The color changes from blue to orange. Which molecule is present?

Which table row correctly identifies the chemical elements present in proteins but NOT usually in fats or carbohydrates?

List the chemical elements that make up all protein molecules, identifying the specific element that is generally absent in carbohydrates and fats.

State the reagents used and the expected positive colour changes for testing the presence of starch and proteins in a food sample.