Question

When molecules move through channels and pumps, they usually: contact the tails of the phosholipids contact amino-acids on the interior of the transmembrane protein contact only the heads of the phospholipids do not contact any amino-acids?

Answer 1

The correct answer is B.
Channels and pumps are transmembrane proteins that create hydrophilic tunnels across the membrane. This allows molecules to be diffused through them. The channels and pumps are highly selective and only allow the diffusion of specific molecules. The channel's structure blocks the contact of the molecule with the head and tail of the phospholipids that form the membrane. As we said, the channels and pumps are proteins, so they are formed by amino acids. Therefore, the molecules passing through channels and pumps, only come in contact with the amino acids.