Muscle cells are grown in a sealed container of nutrient solution. The cells are respiring. Carbon dioxide made in the cells passes across the cell membrane into the solution.
A scientist measured the mean carbon dioxide concentrations at the start and after 25 minutes.
| Time in minutes | Carbon dioxide concentration inside the cells in mmol dm⁻³ | Carbon dioxide concentration in the solution in mmol dm⁻³ |
|---|---|---|
| 0 | 6.2 | 1.4 |
| 25 | 6.0 | 3.3 |
State whether the movement of carbon dioxide from the muscle cells into the solution needs energy released by respiration. Give a reason for your answer.
Calculate the percentage decrease in the concentration gradient for carbon dioxide between 0 minutes and 25 minutes.
The scientist repeats the investigation but replaces the solution with fresh nutrient solution every 5 minutes.
Suggest and explain how this affects the rate at which carbon dioxide leaves the cells, compared with the original investigation.
140 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.