Blood is sampled at two points in a capillary network surrounding skin cells in a mammal. Sample P is taken as blood enters the network and sample Q as it leaves. The samples are equal volumes. The measurements are given per 100 cm3 of blood.
| Sample | Oxygen carried by red blood cells / cm3\mathrm{cm^3}cm3 | Carbon dioxide carried in plasma / cm3\mathrm{cm^3}cm3 |
|---|---|---|
| P | 20.0 | 45.0 |
| Q | 15.0 | 50.0 |
Which statement gives the direction in which each gas diffuses between the blood and the skin cells?
Both oxygen and carbon dioxide diffuse from the blood into the cells
Oxygen diffuses from the cells into the blood and carbon dioxide diffuses from the blood into the cells
Oxygen diffuses from the blood into the cells and carbon dioxide diffuses from the cells into the blood
Both oxygen and carbon dioxide diffuse from the cells into the blood
67 exam-style questions on Edexcel GCSE Biology 8.2 Blood and circulation, covering 8.2.1 Structure and function of the blood, 8.2.2 Structure of blood vessels, 8.2.3 Structure of the heart and circulatory system, and 8.2.4 Cardiac output. Each one has a worked solution and a mark scheme showing where the marks go.