Cell Communication

Cell-cell communication is critical for the function and survival of cells

  • Responsible for the growth and development of multicellular organisms

How do cells communicate?

  • Cells communicate through three general ways:

    1. Direct contact

    2. Local Signaling

    3. Long-distance signaling

Direct contact: communication through cell junctions

  • Signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells

    • Animal cells: gap junctions

    • Plant Cells: plasmodesmata

      • ex. immune cells

Local regulators: a secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extracellular fluid

  • The chemical messages will cause a response in a target cell

    • Ex: paracrine signaling, synaptic signaling

Long-Distance Signaling: Animals and plants use hormones for long distance signaling

  • Plants release hormones that travel in the plant vascular tissue or through air

  • Animals use endocrine signaling: hormones released into circulatory system to interact with target cells

Cell Signaling can be divided into 3 stages:

Reception: ligand binds to receptor

Transduction: Signal is converted

Response: Cell process is altered

Stage 1 Reception: The detection and receiving of a ligand by a receptor in the target cell

  • Receptor: macromolecule that binds to a signal molecule (ligand)

    • All receptors have an area that interacts with the ligand and an area that transmits a signal to another protein

      • Binding between ligand and receptor is highly specific

    • When the ligand binds to the receptor, the receptor activates

    • allows receptor to interact with other cellular molecules via transduction signal

      • can be in the plasma membrane or intracellular

        • plasma membrane receptors: most common, bind to polar and large ligands

        • Intracellular receptors: found in cytoplasm or nucleus, bind to ligands that pass-through plasma membrane like hydrophobic moles

Stage 2 Transduction: the conversion of an extracellular signal to an intracellular signal that will bring a cellular response

  • requires a sequence of changes in a series of molecules known as a signal transduction pathway

    • Signal Transduction Pathway: regulates protein activity

    • REMEMBER: change in shape = change in function

  • Second Messengers: small, non-protein molecules and ions that help amplify the response

Stage 3 Response: the final molecule converts signal to response

  • examples:

    a. proteins that can alter membrane permeability

    b. enzyme that will change a metabolic process

    c. protein that turns genes on or off