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Which of the following criteria does not pertain to facilitated transport?
A. Requirement of special membrane proteins
B. High selectivity
C. Transport saturation
D. Uphill transport

Last updated date: 20th Jun 2024
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Hint: Facilitated transport via the semipermeable membrane is the movement of molecules along its concentration gradient, i.e. Plasma membrane. This is the mechanism of spontaneous passive transport or downhill transport of molecules or ions through unique transmembrane integral proteins across a biological membrane.

Complete answer: Often recognized as facilitated diffusion, passive-mediated transport is facilitated transport. Facilitated transport is a mechanism in which the transfer of molecules takes place along the gradient of concentration, from the higher concentration region to the lower concentration region. The movement of molecules and ions takes place before equilibrium is established. This molecular transport takes place through the semipermeable membrane, i.e. the plasma membrane, through certain integral proteins of the transmembrane that are embedded in the plasma membrane. There are also transmembrane integral proteins known as protein carriers. Facilitated transport is downhill transport because it is a form of passive transport that does not require expenditure on ATP or resources and takes place along the gradient of concentration, i.e. from the area of greater-concentration to the region of lower concentration. Facilitative transport is strongly selective since the transport of any specific molecule or ion involves carrier proteins.
Thus, the correct answer is Option D, i.e., Uphill transport.

Note: Transmembrane integral proteins are often referred to as proteins of the channel or proteins of the carrier. Only one side of the membrane at a time is exposed to these proteins. These proteins bind to and alter the form of the molecules or ions to move the molecules or ions to the other side across the plasma membrane.