Question

Why do channel proteins often fold with nonpolar R groups to the channel's exterior and polar R groups to its interior?

A) Nonpolar R groups on the exterior help anchor the protein in the lipid bilayer.
B) Nonpolar R groups on the exterior prevent unwanted interactions with water molecules.
C) Polar R groups on the interior create a hydrophilic environment for ion transport.
D) Polar R groups on the interior facilitate hydrogen bonding with ions or molecules passing through the channel.
E) Both A and B are correct.
F) Both C and D are correct.
G) All of the above options are correct.

Answer 1

Channel proteins often fold with nonpolar R groups on the exterior and polar R groups on the interior to anchor the protein in the lipid bilayer, prevent unwanted interactions with water molecules, create a hydrophilic environment for ion transport, and facilitate hydrogen bonding with ions or molecules passing through the channel.

Step-by-step explanation:

Channel proteins often fold with nonpolar R groups to the channel's exterior and polar R groups to its interior due to several reasons:

1. Nonpolar R groups on the exterior help anchor the protein in the lipid bilayer: The nonpolar amino acids on the exterior of the channel protein interact with the hydrophobic lipid tails of the phospholipids in the membrane, helping to anchor the protein in the lipid bilayer.
2. Nonpolar R groups on the exterior prevent unwanted interactions with water molecules: The nonpolar amino acids on the exterior of the channel protein repel water molecules, preventing unwanted interactions that could interfere with the function of the channel.
3. Polar R groups on the interior create a hydrophilic environment for ion transport: The polar amino acids on the interior of the channel protein create a hydrophilic environment that attracts and facilitates the passage of ions through the channel.
4. Polar R groups on the interior facilitate hydrogen bonding with ions or molecules passing through the channel: The polar amino acids on the interior of the channel protein can form hydrogen bonds with ions or molecules passing through the channel, aiding in their transport.

Channel proteins have nonpolar R groups on their exterior to anchor them within the lipid bilayer and to avoid interaction with water, while their polar R groups are on the interior to create a hydrophilic environment for selective ion transport.

Channel proteins in cell membranes fold with nonpolar R groups on their exterior and polar R groups on their interior to facilitate their specific functions in a cell's lipid bilayer. Nonpolar R groups face the exterior, helping to anchor the protein within the lipid bilayer due to their hydrophobic nature, which matches the environment of the fatty acid tails in the bilayer (Choice A). These nonpolar groups also act to prevent unwanted interactions with water molecules (Choice B). On the other hand, polar R groups line the interior of the channel to create a hydrophilic environment (Choice C) that is necessary for the transport of polar molecules and ions. They facilitate hydrogen bonding with ions or molecules passing through, which is essential for the protein's selective transport function (Choice D). Therefore, the correct answer is that all the options (G) are correct because they collectively describe why channel proteins have such specific distributions of amino acid side chains.