Fruit juices contain different sugars such as fructose, glucose, and maltose. Different strains of yeast can ferment these sugars to produce ethanol (a fermented product).
Scientists investigated how two different strains of yeast, Strain X and Strain Y, ferment the sugars in a fruit juice sample over 18 hours. The results are shown in the table below:
| Yeast Strain | Substance | Concentration at 0 h (g/100 mL) | Concentration after 18 h (g/100 mL) |
|---|---|---|---|
| Strain X | Glucose | 6.4 | 0.8 |
| Fructose | 7.2 | 3.6 | |
| Maltose | 0.5 | 0.5 | |
| Ethanol | 0.0 | 4.8 | |
| Strain Y | Glucose | 6.4 | 4.8 |
| Fructose | 7.2 | 7.2 | |
| Maltose | 0.5 | 0.5 | |
| Ethanol | 0.0 | 0.8 |
Identify which sugar is not fermented by either strain of yeast.
After 18 hours, how many times greater is the ethanol yield of Strain X compared to Strain Y?
Which sugar is fermented the most by Strain X?
Explain why it would be best to use Strain Y if the goal is to produce a lower-alcohol beverage that retains all of its original fructose.
16 exam-style questions on OCR GCSE Biology 1.3 Respiration, covering 1.3.1 Cellular respiration supplies ATP, 1.3.2 Aerobic and anaerobic respiration, 1.3.3 Sugars and carbohydrates, 1.3.4 Amino acids and proteins, and 1.3.5 Fatty acids and lipids. Each one has a worked solution and a mark scheme showing where the marks go.