A spherical leaf cell has a radius of 10 µm. The rate of O₂ diffusion across its plasma membrane is given by $J = k\,A\,\Delta C$, where $k = 1.2\times10^{-5}$ mol·m⁻²·s⁻¹·(mol·m⁻³)⁻¹, $A$ is the surface area and $\Delta C$ is the concentration difference. The external O₂ concentration is 0.21 mol·m⁻³ and the internal concentration is 0.05 mol·m⁻³.\n\nA cylindrical leaf cell has the same volume as the sphere but a length of 30 µm. Determine the radius of the cylinder, compute the O₂ diffusion rate for each cell, and state which cell type allows the greater O₂ influx. Give the diffusion rates in $\times10^{-15}$ mol·s⁻¹ to two decimal places.

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Sphere: 2.41×10⁻¹⁵ mol·s⁻¹; Cylinder: 2.95×10⁻¹⁵ mol·s⁻¹; Cylinder has the higher rate

Neco Model Questions Vol1 2023 Biology Question 38

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