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

Testing for biological molecules — practice question

To test for non-reducing sugars, a second Benedict’s test must be done. Which sequence of steps gives the correct procedure for testing for non-reducing sugar before performing the second Benedict’s test?

  • APerform the Benedict’s test, which gives a negative result. Warm gently with dilute hydrochloric acid. Neutralise with sodium hydrogencarbonate.
  • BPerform the Benedict’s test, with the colour of the solution remaining red. Boil with dilute hydrochloric acid. Neutralise with sodium hydrogencarbonate.
  • CPerform the Benedict’s test, with the colour of the solution remaining blue. Boil with dilute hydrochloric acid. Neutralise with sodium hydrogencarbonate.
  • DPerform the Benedict’s test, which gives a negative result. Neutralise with sodium hydrogencarbonate. Warm gently with dilute hydrochloric acid.

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