Question

43. Cell membranes are fluid, and thus proteins can diffuse laterally within the lipid bilayer. However, sometimes the cell needs to localize proteins to a particular membrane domain. Name four mechanisms that a cell can use to restrict a protein to a particular place in the cell membrane.

Answer 1

Cells use several mechanisms to localize membrane proteins to specific domains, including anchoring to the cytoskeleton, binding to the extracellular matrix, creating protein complexes, and post-translational modifications.

Step-by-step explanation:

Cell membranes are dynamic structures composed of a lipid bilayer embedded with various membrane proteins. While the membrane is fluid, allowing for lateral protein movement, cells can localize proteins to specific membrane domains using several mechanisms:

1. Anchor proteins to the cytoskeleton through direct interactions, limiting their diffusion.
2. Bind proteins to extracellular matrix molecules, which restricts movement outside the cell.
3. Promote protein-protein interactions, creating complexes that are less mobile.
4. Employ post-translational modifications such as the addition of lipid moieties that anchor proteins to particular regions.

These mechanisms ensure proteins function at the correct location in the cell membrane, playing crucial roles in cellular processes such as transport, signaling, and intercellular interactions. For example, integral proteins span across the bilayer, providing a passage for ions and polar molecules, while peripheral proteins are associated with the membrane surfaces and can be involved in signaling or support structures.