A-LevelBiologyBiological moleculesOct/Nov 2017Paper 1 Q71 Mark
A student carried out four tests for biological molecules on a sample of milk. The tests and their results were as follows. • Heating to 80 °C with Benedict's solution gave a brick red colour. • Adding Biuret solution gave a purple colour. • Adding iodine solution gave an orange colour. • Boiling with acid, followed by neutralisation, then heating to 80°C with Benedict's solution gave a brick red colour. Which biological molecules must be present in the milk? 1 non-reducing sugars, 2 protein, 3 reducing sugars, 4 starch
A1, 2 and 3
B1 and 2 only
C2 and 3 only
D3 and 4
✓ Correct Answer
The correct answer is C: 2 and 3 only
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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