Final answer:
Surface proteins bind to transmembrane proteins through non-covalent interactions, anchoring them to the plasma membrane for various functions such as signal transduction and cell communication.
Step-by-step explanation:
The bond that surface proteins have with transmembrane proteins is often non-covalent and involves interactions between the hydrophobic domains of integral membrane proteins and the hydrophobic core of the plasma membrane. These interactions can anchor the protein to one side of the membrane or allow it to span across the entire membrane, serving different functional roles, such as signal transduction, cell communication, and cellular adhesion. Some surface proteins, known as peripheral proteins, are bound to the membrane by interactions with the polar phosphate groups of phospholipids, or with the polar domains of integral membrane proteins. In the case of cell-surface receptors, these transmembrane proteins bind to external ligand molecules and enable cell-specific signalling without the ligand needing to enter the cell.