Industrial microbiologists can use different strains of bacteria to ferment sugars in a bioreactor to produce biofuels such as butanol.
Scientists investigated how two genetically modified strains of bacteria, Strain Alpha and Strain Beta, ferment different carbon sources in a medium over 24 hours. The results are shown in the table below:
| Microbial Strain | Carbon Source | Concentration at 0 h (g/L) | Concentration after 24 h (g/L) |
|---|---|---|---|
| Strain Alpha | Galactose | 8.4 | 1.2 |
| Sucrose | 5.6 | 4.2 | |
| Xylose | 1.5 | 1.5 | |
| Butanol | 0.0 | 6.0 | |
| Strain Beta | Galactose | 8.4 | 5.6 |
| Sucrose | 5.6 | 5.6 | |
| Xylose | 1.5 | 1.5 | |
| Butanol | 0.0 | 1.5 |
Identify which carbon source is not fermented by either strain of bacteria.
After 24 hours, how many times greater is the butanol yield of Strain Alpha compared to Strain Beta?
Which carbon source is fermented the most by Strain Alpha?
Explain why it would be best to use Strain Beta if the goal is to produce a low-butanol solution while retaining all of the original sucrose.
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.