The Xenopus laevis oocyte is roughly 1mm in diameter. After fertilization, it un

Question

The Xenopus laevis oocyte is roughly 1mm in diameter. After fertilization, it undergoes mitosis, a process requiring the coordination of proteins at various locations within the large cell.

a) If this event were coordinated by diffusion alone, estimate how long it would take for a message to reach from one side of the cell to the other if it was passed through a Ca2+ ion?

b) How long would it take for a message to be transmitted through the diffusion of a small protein?

c) How long would it take if the message to reach the other side of the cell if it were carried on a transmembrane protein with diffusion coefficient of 0.2

Explanation / Answer

Time in a diffusion controlled transportation is given by, t = diffusion length2/diffusion coefficient

a) Message carried by Ca2+ ions: Ca2+ ions are smaller in size and there are Ca2+ channels, we can assume the information is passed diagonally across the cell. Therefore the diffusion length is 1000 micrometers. If diffusion coefficient of Ca2+ is known then time taken can calculated.

b) Information regarding the diffusion coefficient of the protein is needed.

c) Diffusion coefficient of transmembrane protein = 0.2 micrometer2/sec. Diffusion length is half the circumference of the cell, which is, pi*r = 1570.8 micrometers.

time = 1570.82/0.2 = 1.234x107 sec or 20.4 weeks.

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