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Biomolecules and Enzymes
Quick questions on Food tests: N(A)-Level Biology Biomolecules
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the starch test (iodine test)?Show answer
Add a few drops of iodine solution to the food sample. Iodine solution is orange-brown. If starch is present, it turns blue-black. If no starch is present, it stays orange-brown.
What is the reducing sugar test (Benedict's test)?Show answer
Add Benedict's solution to the food sample and heat it in a hot water bath. Benedict's solution is blue. If a reducing sugar (such as glucose) is present, the colour changes from blue to green, then orange, and finally brick-red. The more sugar, the further the colour change goes.
What is the protein test (Biuret test)?Show answer
Add Biuret solution to the food sample (this contains sodium hydroxide and copper sulfate). Biuret solution is blue. If protein is present, it turns purple (violet). If no protein is present, it stays blue.
What is the fat test (ethanol emulsion test)?Show answer
Add ethanol to the food sample and shake, then pour the mixture into a tube of water. If fat is present, a white, cloudy (milky) emulsion forms. If no fat is present, the liquid stays clear.
What is q1?Show answer
State the reagent used to test for starch and the positive colour change. [2 marks]
What is q2?Show answer
Explain why the Benedict's test must be heated. [1 mark]
What is q3?Show answer
Describe the test for fat and the positive result. [2 marks]
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