Cell adhesion molecules (CAMs) are cell-surface proteins that allow cells to attach to one another, helping individual cells form stable, organized tissues. Different forms of CAM are involved in different types of cell to cell junction.
How CAMs Work
CAMs are generally membrane proteins with an extracellular region projecting from the plasma membrane. This region can bind to a compatible CAM on an adjacent cell, creating an attachment between the two cells.
Multiple CAM interactions produce stronger adhesion than a single interaction. Inside the cell, CAMs may also connect with structural proteins, helping the junction resist mechanical forces and maintain the organization of the tissue.
| Role of CAMs | Biological consequence |
|---|---|
| Binding adjacent cells | Cells remain connected within a tissue |
| Forming different cell to cell junctions | Junctions can perform different functions in different tissues |
| Linking adhesion to internal cell structure | Mechanical forces can be distributed across cells |
| Supporting selective recognition | Appropriate cell types can organize together |
For example, epithelial cells must remain attached to form continuous sheets covering body surfaces or lining organs. Their junctions help maintain tissue structure while allowing the tissue to function as an organized unit rather than as isolated cells.
A common misconception is that CAMs are the phospholipids that make membranes stick together. This is incorrect: CAMs are proteins associated with the plasma membrane, whereas phospholipids form the bilayer itself. Another mistake is to assume that only one CAM exists; different forms are used in different cell to cell junctions.
Exam Technique
This is Additional Higher Level (AHL) content in B2.1 Membranes and membrane transport. For an “explain” question, link the steps clearly: CAMs in the plasma membranes of neighbouring cells bind, cell to cell junctions form, and cells adhere to produce organized tissues. Detailed names and molecular structures of individual CAM families or junction types are not required by the syllabus.