Final answer:
Different receptors on cells allow the same signaling molecule to elicit distinct responses in each cell type, based on unique receptor interactions with their respective downstream signaling pathways and signal integration processes.
Step-by-step explanation:
The presence of different receptors allows the same signaling molecule to have very different effects on different target cells. This variation in cellular response is due to each cell type expressing a unique set of proteins, including signal receptors like G-protein-linked receptors, ligand-gated ion channels, voltage-gated ion channels, and receptor tyrosine kinases.
These receptors may bind the same ligand, but they activate different responses due to distinct signaling components within each cell type. Furthermore, cells often use the same second messengers but yield divergent outcomes because of these differences in receptor and downstream signaling pathway interactions. The complexity is increased by the process of signal integration, where multiple signals from different cell-surface receptors converge to prompt a unified cellular response, ensuring a coordinated and appropriate reaction to external stimuli.