What phenomenon limits the transport rate in facilitated diffusion if the concentration of the transported substance becomes extremely high?

Answer

Saturation kinetics: all available carrier or channel proteins become fully occupied.

Because facilitated diffusion depends on a finite number of specific proteins, once every protein is occupied transporting substrate, increasing the external concentration further will not increase the transport rate.

What phenomenon limits the transport rate in facilitated diffusion if the concentration of the transported substance becomes extremely high?

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In Da Club - Membranes & Transport: Crash Course Biology #5

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