What caused the sea level change allowing arctic hunters into the americas

The small molecule cyclic amp (camp) takes about 0.2 second to diffuse 10 μm, on average, in a cell. suppose that camp is produced near the plasma membrane on one end of the cell; how long will it take for this camp to diffuse through the cytosol and reach the opposite end of a very large cell, on average? assume that the cell is 200 μm in diameter.

How do all types of diffusion/passive transport actually ‘work’ without using even the smallest amount of cellular energy?

How energy move through ecosystem ?