A student cuts 10 small discs from a spinach leaf. She removes the air from the discs so that they sink in sodium hydrogencarbonate solution.
When light shines on the discs, they slowly float to the surface.
She records the time taken for 5 of the discs to float, with a lamp at different distances.
The Table shows her results.
Table
| Distance of lamp in cm\text{cm}cm | Trial 1 time in minutes | Trial 2 time in minutes | Trial 3 time in minutes | Mean time in minutes |
|---|---|---|---|---|
| 10 | 4.0 | 4.4 | 4.2 | 4.2 |
| 20 | 6.8 | 7.2 | 7.0 | 7.0 |
| 30 | 11.5 | 12.1 | 18.6 | |
| 40 | 16.2 | 15.8 | 16.6 | 16.2 |
Identify the anomalous result in the Table.
Calculate the mean time for 30 cm.
The rate of photosynthesis can be calculated using: rate =1mean time\displaystyle = \frac{1}{\text{mean time}}=mean time1
Calculate the rate of photosynthesis at 20 cm.
Give your answer to 2 significant figures.
Explain why the leaf discs float when light shines on them.
Suggest why the discs are put in sodium hydrogencarbonate solution rather than in water.
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.