The diffusion constant of ATP is 3.0 × 10–10 m2/s. How long would it take for ATP to diffuse across an average cell of 15 μm diameter in seconds?
Large amounts of water are given off by plants. Inside a leaf, water vapour diffuses through small openings called stomatal pores. The diffusion constant for water vapour in air is D = 2.4 × 10–5 m2/s.
Assume the stomatal pore is a cylindrical tube of radius 5.5 μm and length 30 μm. If the concentration of water vapour on the interior side of the pore is 0.022 kg/m3 and the concentration on the outside is 0.011 kg/m3, what is the mass of water (in kg) vapour that passes through a single stomatal pore in one hour?