Question

channel proteins:
a utilize the g protein complex to function
b are found only on endoplasmic reticulum
c allow cells to recognize one another
d provide a tunnel through which ions or molecules can enter or leave the cell
e are binding sites for other molecules

Explanation:

Channel proteins are integral membrane proteins. They form hydrophilic channels. These channels allow specific ions or small molecules to pass through the cell membrane. This is a key function of channel proteins.

• Option A: G - protein complex is not related to the basic function of channel proteins.
• Option B: Channel proteins are not only on the endoplasmic reticulum but also on the plasma membrane and other membranes.
• Option C: Cell - cell recognition is mainly the function of glycoproteins, not channel proteins.
• Option E: Binding sites for other molecules are more characteristic of receptor proteins rather than channel proteins.

Answer:

D. provide a tunnel through which ions or molecules can enter or leave the cell