Understand the context: Membrane receptors are specialized proteins embedded in the cell membrane that allow cells to communicate with their environment by receiving and transmitting signals.
Identify the key question: The problem asks for the three main subclasses of membrane receptors, which are involved in signal transduction rather than transport or structural roles.
Clarify the options: Eliminate choices that do not align with the function of membrane receptors. For example, 'Transporters, pumps, symporters' and 'Carrier proteins, channel proteins, anchor proteins' are related to transport and structural roles, not signal transduction.
Focus on the correct answer: The three main subclasses of membrane receptors are 'G protein-coupled receptors, ion channel-linked receptors, enzyme-linked receptors,' as these are directly involved in signal transduction pathways.
Conclude: Peripheral proteins, integral proteins, and lipid-anchored proteins are classifications based on membrane association, not receptor function. Therefore, they are not relevant to the question.