Researchers grow living tissue in a nutrient solution. Oxygen enters the tissue only through surfaces touched by the solution.
In arrangement Q, the six pieces are kept apart so that the solution touches every face.
| Arrangement | Number of pieces | Dimensions of each piece in mm\text{mm}mm | Total volume of tissue in mm3\text{mm}^3mm3 |
|---|---|---|---|
| P | 1 | 1.2×0.4×0.41.2 \times 0.4 \times 0.41.2×0.4×0.4 | 0.192 |
| Q | 6 | 0.2×0.4×0.40.2 \times 0.4 \times 0.40.2×0.4×0.4 | 0.192 |
Cells more than 0.15 mm from an exposed surface cannot receive oxygen quickly enough by diffusion.
Calculate the total surface area : volume ratio for each arrangement.
Give each ratio in the form n:1n:1n:1.
Explain which arrangement can keep all its cells supplied with oxygen by diffusion alone.
114 exam-style questions on OCR GCSE Biology 2.2 The challenges of size, covering 2.2.1 Exchange surfaces and surface area : volume ratio, 2.2.2 Substances transported in organisms, 2.2.3 The human circulatory system, 2.2.4 The heart and blood vessels, 2.2.5 Red blood cells and plasma, 2.2.6 Uptake of water and mineral ions by plants, 2.2.7 Transpiration and translocation, 2.2.8 Xylem and phloem, 2.2.9 Environmental factors and water uptake, and 2.2.10 Using a potometer. Each one has a worked solution and a mark scheme showing where the marks go.