Question

Which of the following criteria does not pertain to facilitated transport?

• A. Transport saturation
• B. Uphill transport
• C. Requirement of special membrane proteins
• D. High selectivity

Answer 1

The correct option is B Uphill transport

Facilitated transport (facilitated diffusion) is the movement of molecules or ions across a biological membrane through the membrane proteins. These proteins are very selective and only transport specific molecules. The proteins involved in facilitated diffusion are channel proteins, gated channel proteins and carrier proteins. Channel proteins form pores in the membrane through which the substances get transported. The carrier proteins bind to molecules that need to be transported and undergo changes in their structure so as to move the molecules on to the other side of the membrane.
In facilitated diffusion, movement of molecules occur along the concentration gradient, that is from higher to lower concentration (downhill transport) without expenditure of any energy. In uphill transport, the movement of molecules is against the concentration gradient (lower to higher concentration) using energy in the form of ATP.
The number of membrane proteins is limited and hence they can be saturated if the concentration of molecules to be transported is high.