CAIE A Level Biology 9700 · Biological molecules

Biological molecules: describe question

Describe4 marksStandard

A student performed biochemical tests on four unknown solutions (P, Q, R, and S). The results are shown in the table below.

Solution	Benedict's test (before hydrolysis)	Benedict's test (after acid hydrolysis)	Iodine test	Emulsion test	Biuret test
P	Blue	Blue	Blue-black	Cloudy white	Purple
Q	Orange-red precipitate	Orange-red precipitate	Brown	Clear	Blue
R	Blue	Orange-red precipitate	Brown	Clear	Purple
S	Blue	Blue	Brown	Clear	Blue

Describe the biological molecules present in each solution. Use the results in the table to support your answer.

How this question is marked

4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

Biological molecules: describe question

How this question is marked

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