Quantitative – diffusion time: Consider a spherical, single-celled organism which needs oxygen to
survive.
a. Assume oxygen needs to diffuse from the outside of the cell to its center. Write an equation that
gives the diffusion time in terms of the cell radius.
b. The cell has a 4 micron (m) diameter, and diffusion coefficient of oxygen is 1.8 x 10-5 cm2/s in
water (assume diffusion is the same through the cell membrane). How long does it take for oxygen
to diffuse to the center of the cell?
c. Cells typically need key molecules such as oxygen to survive. Diffusion times of oxygen can limit
how big cells can become. If the cell gets too large for oxygen to reach its center, the cell could
die. Calculate the size of a cell at which oxygen diffusion time becomes too slow and so limits the
ability of the cell to get that big. Explain your assumptions. How does this compare to typical cell
sizes?
Trending now
This is a popular solution!
Step by step
Solved in 4 steps
