A scientist investigates photosynthesis using equal masses of an aquatic moss. Each sample is placed in a transparent chamber connected to a gas syringe and illuminated for 5.0 minutes5.0\ \text{minutes}5.0 minutes using the same lamp. The temperature is kept at 25 ∘C25\ ^\circ\text{C}25 ∘C.
The scientist repeats the investigation using solutions that provide a lower and a higher carbon dioxide concentration.
The results are shown in the table.
| Distance of lamp in cm\text{cm}cm | Volume of oxygen at lower carbon dioxide concentration in cm3\text{cm}^3cm3 | Volume of oxygen at higher carbon dioxide concentration in cm3\text{cm}^3cm3 |
|---|---|---|
| 10 | 3.0 | 5.6 |
| 20 | 2.8 | 2.8 |
| 40 | 0.70 | 0.70 |
Calculate the increase in the rate of oxygen production at 10 cm when the higher carbon dioxide concentration is used.
Give your answer to 2 significant figures.
Explain how the results show that the limiting factor changes as the distance of the lamp is decreased from 40 cm to 10 cm.
The lamp is moved from 40 cm to 80 cm while the higher carbon dioxide concentration is used.
Predict the volume of oxygen expected in 5.0 minutes5.0\ \text{minutes}5.0 minutes, assuming that the relationship between distance and oxygen volume shown by the results at 20 cm and 40 cm continues.
Give your answer to 2 significant figures.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.