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Overview of Cell Surface Receptors quiz #1

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  • What are the three main types of cell surface receptors, and what is the primary function of each?
    The three main types are ion channel-coupled receptors (convert chemical/electrical signals, important in nerve signaling), G protein-coupled receptors (activate G proteins to trigger signaling cascades), and enzyme-coupled receptors (often protein kinases that act as enzymes to activate downstream targets).
  • How do ion channel-coupled receptors contribute to nerve signaling?
    Ion channel-coupled receptors respond to electrical or chemical gradients by allowing ions to pass through the membrane, converting chemical signals into electrical signals or vice versa, which is crucial for nerve signaling.
  • What happens when a ligand remains bound to a cell surface receptor for an extended period?
    If a ligand remains bound for a long time, the cell may downregulate the receptor by removing it from the plasma membrane to decrease the cell's response to the persistent signal.
  • What is the role of G protein-coupled receptors in cellular signaling?
    G protein-coupled receptors activate G proteins in the cytosol upon ligand binding, initiating a signaling cascade that can affect enzymes, ion channels, or other proteins within the cell.
  • How do enzyme-coupled receptors typically function after activation?
    Enzyme-coupled receptors, often protein kinases, act as enzymes (usually in the cytosolic domain) upon activation, forming complexes that trigger downstream signaling events.
  • What is a second messenger, and what role does it play in signal transduction pathways?
    A second messenger is a molecule that acts downstream of the receptor-ligand interaction to propagate the signal by activating additional proteins in the signaling pathway.
  • What is the general sequence of events in a signal transduction pathway initiated by a cell surface receptor?
    A ligand binds to a receptor, activating it; the receptor then activates a series of proteins (often involving second messengers), culminating in the activation of a transcription factor that alters gene expression.
  • How do protein kinases and phosphatases regulate signaling pathways involving cell surface receptors?
    Protein kinases add phosphate groups to proteins (activating or inhibiting them), while phosphatases remove phosphates, thus regulating the activity of proteins throughout the signaling pathway.
  • What is the ultimate cellular outcome of most signal transduction pathways initiated by cell surface receptors?
    Most signal transduction pathways ultimately activate a transcription factor, leading to changes in gene expression that affect cellular functions such as survival, apoptosis, proliferation, or differentiation.
  • Why might a cell need to downregulate its surface receptors?
    A cell may downregulate its surface receptors to reduce its sensitivity to a persistent or excessive extracellular ligand, preventing overstimulation of signaling pathways.
  • What is a common feature shared by all three main types of cell surface receptors in their signaling mechanisms?
    All three types are typically activated by binding to an extracellular ligand, which initiates a signaling cascade involving protein kinases and second messengers.
  • How do signal transduction pathways ensure specificity and amplification of cellular responses?
    Signal transduction pathways involve multiple sequential steps, where each activated protein can activate several downstream targets, ensuring both specificity and amplification of the signal.
  • What is the significance of transcription factors in the context of cell surface receptor signaling?
    Transcription factors are the final targets in many signaling pathways, and their activation leads to changes in gene expression that determine the cell's response to external signals.
  • What determines whether a cell is responsive to a particular hormone?
    A cell is responsive to a particular hormone if it expresses the specific cell surface receptor that can bind to that hormone (ligand). The presence of the appropriate receptor on the cell membrane allows the cell to detect and respond to the hormone's signal.