Question
Identify a type of molecular movement which is highly selective and requires special membrane proteins, but does not require energy.
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Answer
The type of molecular movement which is highly selective and require special membrane proteins, but does not require energy is called facilitated diffusion. Diffusion of any substance across a membrane depends on its solubility in lipid. If a substance has hydrophilic moiety, it cannot diffuse through a membrane. To facilitate the diffusion of such a molecule, special membrane proteins are present. In this case also, diffusion takes place from higher concentration to lower concentration and hence energy is not spent in the form of ATP. Facilitated diffusion is highly selective. It allows cells to select particular substances.
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