O-LevelBiologyRespiration5090/11 · Oct/Nov 2011 · Q271 Mark

Two containers, X and Y, were filled with equal amounts of dough mixture for making bread. The mixture in Y had yeast in it. The containers were then left in a warm place for two hours. The diagram shows their appearance after this time. Which substance produced by the yeast causes the difference between containers X and Y? [Figure 27.1]

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Aalcohol

Bcarbon dioxide

Clactic acid

Doxygen

✓ Correct answer

B: carbon dioxide

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Topic: Respiration, O-Level Biology (syllabus 5090). Multiple choice, 1 mark.
Source: O-Level Biology, Oct/Nov 2011 Paper 1 Variant 1, question 27.

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