Biology 9700 · AS & A Level · Testing for biological molecules

Testing for biological molecules — practice question

Samples of biological molecules are examined for sugars. The table gives the conditions used and the outcomes after each test. Solution 1: heated with Benedict’s solution → blue; boiled with hydrochloric acid, neutralised, then heated with Benedict’s solution → yellow. Solution 2: heated with Benedict’s solution → green; boiled with hydrochloric acid, neutralised, then heated with Benedict’s solution → orange. Solution 3: heated with Benedict’s solution → orange; boiled with hydrochloric acid, neutralised, then heated with Benedict’s solution → red. Which may contain reducing sugars?

  • A1, 2 and 3
  • B1 and 3 only
  • C2 and 3 only
  • D1 only

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