Ch. 9

• Ligand: smaller molecule that binds to larger molecule
• G-protein coupled receptors: large family of cell-surface receptors that help mediate signaling within the cell
• Cellular receptors

  • Main types of cellular receptors
  • Cell-surface receptors
  • Intracellular receptors
  • Cell surface receptors are Located on the cell membrane, and bind to extracellular ligands to initiate signal transduction
  • Intracellular receptors are Generally found in cytoplasm or nucleus and are involved in regulating gene expression in response to signals
• Signal transduction and intracellular signaling (1/2)

  • Intracellular receptors interact with hydrophobic ligands to help regulate gene expression
• Signal transduction and intracellular signaling (2/2)

  • The process of signal transduction has 3 main steps:

  1. Ligand binding:
  2. The cellular signals begin and specific ligands bind to their respective receptors which initiates the signal transduction process
  3. Receptor activation:
  4. Occurs after ligand binding. The receptors undergo conformation changes which triggers intracellular cascades that propagate the signal
  5. Intracellular signaling:
  6. Signal transduction pathways relay the message using intricate signaling molecules and amplification mechanisms
• • G-Protein Coupled Receptors span the cell membrane and has extracellular (outside the cell) ligand binding domains and intracellular (within the cell) signaling domains
  • Regulate effector proteins or ion channels
  • Work as intermediaries in signal transduction to help pathway continue
  • Initiate intracellular responses
• • In multicellular organisms, communication serves several purposes

  1. Developmental processes: guides intricate processes like organ formation
  2. Immune response: coordinate activity of immune cells, initiate defense
  3. Homeostasis maintenance: maintain physiological balance within multicellular organisms