Final answer:
Water-soluble ligands, which are polar and sometimes too large, bind to cell-surface receptors on the cell membrane. These ligands include small molecules, peptides, and proteins and are essential for signal transduction.
Step-by-step explanation:
The type of ligands that will bind to receptor proteins on the cell membrane, also known as cell-surface receptors, are typically water-soluble ligands. These ligands are polar and cannot diffuse through the plasma membrane on their own. As a result, they interact with the extracellular domain of membrane receptors. Water-soluble ligands include a diverse group of molecules such as small molecules, peptides, and proteins. These ligands are crucial for signal transduction, in which an external signal is transformed into an internal one, triggering a response within the cell.
Due to their size and polarity, these ligands require cell-surface receptors to relay their message into the cell. These receptors span the plasma membrane, and upon ligand binding, can induce a series of reactions leading to physiological changes. Cell-surface receptors are integral proteins that also serve as markers, specific to individual cell types, and involve various responses, including the opening of ion channels or interaction with proteins like G-proteins to propagate the signal.