key term - Cell-surface receptors

Definition

Cell-surface receptors are specialized protein molecules located on the outer membrane of cells that bind to signaling molecules, such as hormones or neurotransmitters, to initiate a cellular response. These receptors play a critical role in cell communication and signal transduction, allowing cells to respond appropriately to their environment and coordinate various physiological processes.

5 Must Know Facts For Your Next Test

1. Cell-surface receptors can be classified into different types based on their structure and function, including G-protein coupled receptors, ion channel receptors, and enzyme-linked receptors.
2. The binding of a ligand to a cell-surface receptor often leads to conformational changes in the receptor, which triggers intracellular signaling cascades that result in various cellular responses.
3. Different cell types can have unique sets of cell-surface receptors, allowing them to respond specifically to different signals and perform specialized functions.
4. Desensitization is a process where prolonged exposure to a ligand can decrease receptor activity, preventing overstimulation and helping maintain cellular homeostasis.
5. Cell-surface receptors are involved in many critical biological processes, including immune responses, growth regulation, and neurotransmission.

Review Questions

• How do cell-surface receptors contribute to the process of signal transduction in cells?
  • Cell-surface receptors play a pivotal role in signal transduction by binding specific ligands that trigger conformational changes in the receptor. This alteration activates various intracellular signaling pathways, leading to cellular responses such as gene expression changes or metabolic adjustments. By effectively relaying external signals into the cell, these receptors help maintain homeostasis and regulate vital physiological processes.
• Compare and contrast the functions of different types of cell-surface receptors, such as GPCRs and enzyme-linked receptors.
  • G-protein coupled receptors (GPCRs) function by activating G-proteins upon ligand binding, initiating complex signaling cascades that can affect multiple pathways. In contrast, enzyme-linked receptors typically have intrinsic enzymatic activity or are associated with enzymes; when ligands bind, they trigger phosphorylation events that directly influence cellular activities. While both types facilitate communication between the extracellular environment and the cell's interior, their mechanisms and outcomes vary significantly.
• Evaluate the significance of ligand binding and receptor desensitization in maintaining cellular homeostasis.
  • Ligand binding is crucial for initiating cellular responses; however, prolonged exposure can lead to receptor desensitization, where receptors become less responsive to continued stimulation. This mechanism is essential for maintaining cellular homeostasis as it prevents overstimulation and allows cells to adapt to changing environments. By regulating receptor sensitivity through desensitization, cells can balance responsiveness to signals while avoiding excessive reactions that could disrupt physiological equilibrium.

Related terms

Ligands:

Ligands are molecules that bind specifically to receptors, triggering a response in the target cell. They can include hormones, neurotransmitters, and other signaling molecules.

Signal transduction: Signal transduction refers to the process by which a cell converts an external signal, received through its receptors, into a functional response. This often involves a series of molecular events within the cell.

G-protein coupled receptors (GPCRs): GPCRs are a large family of cell-surface receptors that respond to various external signals and activate intracellular signaling pathways through G-proteins.