Role of Transport Proteins in Ion Transport

Cell membranes are crucial components of all living cells, serving not only as barriers but also as facilitators of communication and transport. The fluid mosaic model describes the cell membrane as a dynamic structure composed of various lipids and proteins that float in or on the fluid lipid bilayer. One specific type of protein that exists within the cell membrane provides channels for the passage of specific ions and molecules.

Which of the following types of proteins primarily facilitate the transport of ions across the cell membrane?