Final answer:
Cells adjust their response to external signals using cell-surface receptors and signal transduction pathways, which can activate or inhibit gene expression and lead to a wide range of cellular responses, including apoptosis. The complexity of these responses can be due to signal integration and variations in protein expression. Malfunctions in these pathways can result in disease.
Step-by-step explanation:
Cells modulate their sensitivity to extracellular signals through various mechanisms involving cell-surface receptors, signal transduction pathways, and the regulation of gene expression. When an extracellular molecule, such as a hormone or a nutrient, binds to a receptor on the cell membrane, it triggers a cascade of events that ultimately leads to changes in the cell's function. This may involve altering the cell's metabolism, enabling or inhibiting cell growth, and even initiating apoptosis (programmed cell death).
Different cells can exhibit varied responses to the same signal due to differences in receptor types and protein expression. The complexities of cellular responses are also shaped by signal integration, where signals from multiple receptors can converge to produce a coherent response. Furthermore, some receptors can bind to multiple types of ligands, indicating the versatility of cellular communication.
Errors in receptor function or structure can have profound effects, potentially leading to various diseases, including cancer and heart disease. The intricate system of cellular signaling is essential for maintaining normal cellular function and responding appropriately to environmental changes.