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Cell Communication and Signal Transduction in General Biology

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Termini in questo insieme (21)

  • Four Essential Elements for Cell Communication

    Signaling cell releases signaling molecules; responding cell has receptor proteins in membrane or cytosol that bind signaling molecules.

  • Steps of a Signaling Pathway

    1. Receptor Activation (signal binds receptor)
    2. Signal Transduction (signal transmitted inside cell)
    3. Response (cell acts)
    4. Termination (signal ends)

  • Paracrine Signaling

    Signal diffuses to nearby cells; important in embryonic development and neurotransmission; signals growth, division, differentiation.

  • Autocrine Signaling

    Cell produces a signal and also responds to its own signal.

  • Contact-Dependent Signaling

    Both cells have receptors that physically interlock to transmit signals.

  • Endocrine Signaling

    Signals travel long distances through bloodstream to target cells with specific receptors; examples include adrenaline, testosterone, estrogen.

  • Cognate Receptor

    A receptor that specifically recognizes and binds a particular signaling molecule.

  • Hormones

    Information-carrying molecules secreted by cells, circulate in body, act on distant target cells; vary widely in chemical structure.

  • Location of Hormone Receptors

    Steroid hormone receptors are inside the cell; most other signal receptors are in the plasma membrane.

  • Ligands

    Signaling molecules that bind only to cells with the correct (cognate) receptor.

  • Steroid Hormone Signaling

    Lipid-soluble steroid hormones bind receptors inside the cell and directly alter gene expression by hormone-receptor complex entering nucleus.

  • Signal Transduction for Lipid-Insoluble Hormones

    These hormones cannot cross the plasma membrane and rely on signal transduction pathways at the cell surface to relay and amplify the signal inside the cell.

  • G Protein-Coupled Receptors (GPCRs)

    Seven-transmembrane receptors that undergo conformational change when activated and trigger intracellular signaling via G proteins.

  • G Protein Activation Cycle

    Inactive when bound to GDP; activated when receptor causes GDP to be exchanged for GTP; active G protein then activates enzymes producing second messengers.

  • cAMP Signaling Pathway via GPCR

    Adenylyl cyclase converts ATP to cAMP, which activates protein kinase A to phosphorylate target proteins.

  • IP3 Signaling Pathway via GPCR

    Activated G protein activates phospholipase C, producing IP3 which releases Ca2+ from SER; both IP3 and Ca2+ act as second messengers.

  • Receptor Tyrosine Kinases (RTKs)

    Enzyme-linked receptors that dimerize and autophosphorylate on tyrosine residues upon ligand binding, creating docking sites for signaling proteins.

  • Kinase vs Phosphatase

    Kinase adds phosphate groups to proteins (usually activating them); phosphatase removes phosphate groups (usually deactivating proteins).

  • MAP Kinase Pathway

    RTK activation triggers Ras (a G protein) to activate a phosphorylation cascade of kinases, amplifying the signal and regulating gene expression for growth and division.

  • Signal Termination Mechanisms

    Signal molecule detaches from receptor, G protein hydrolyzes GTP to GDP, enzymes degrade cAMP, and phosphatases remove phosphate groups to stop signaling.

  • Two General Types of Signal Responses

    1. Change in gene expression
    2. Activation or deactivation of existing target proteins in the cell.