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

Testing for biological molecules — practice question

A student performed four biological molecule tests on a milk sample. The tests and outcomes were: heating to $80^{\circ}\text{C}$ with Benedict’s solution produced a green colour; adding Biuret solution produced a purple colour; adding iodine solution produced an orange colour; boiling with acid, then neutralising, and afterwards heating to $80^{\circ}\text{C}$ with Benedict’s solution produced a brick red colour. Which conclusion drawn from these results is correct?

  • Aonly protein and reducing sugar present
  • Bonly protein and non-reducing sugar present
  • Conly protein, reducing sugar and non-reducing sugar present
  • Donly starch, protein and sugar present

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