page 06 10. The alveoli of vertebrate lungs have thin walls, constructed of a single layer of epithelial cells, which allow rapid diffusion of gases. The rate of diffusion of oxygen across exchange surfaces can be calculated using the following formula: 1 2 C C Rate P A T ( )     where: P is the permeability constant A is the surface area C1 is the higher concentration C2 is the lower concentration T is the thickness of the exchange surface. A section of alveolar epithelium has a surface area of 2.2 μm2 and is 1.0 μm thick. The permeability constant of the epithelium for oxygen is 0.012 s−1. The concentration of oxygen on one side of the epithelium is 2.3 × 10−16 mol μm−3 and the concentration on the other side is 9.0 × 10−17 mol μm−3. What is the rate of diffusion of oxygen across this alveolar epithelium? A 1.8 × 10−1 mol μm−2 s−1 B 2.3 × 10−16 mol μm−2 s−1 C 1.8 × 10−18 mol μm−2 s−1 D 3.7 × 10−18 mol μm−2 s−1 11. Red‑green colour deficiency is a sex‑linked condition caused by a recessive allele. The diagram shows the inheritance of this condition in a family. Key affected male affected female unaffected male unaffected female R S T U Using the information given in the diagram, which of the females must be carriers of red‑green colour deficiency? A S only B R and S only C R, S and T only D R, S, T and U