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Lecture 7

BIO230Lecture 7.docx

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Jennifer Harris

BIO230 Lecture 7 879-883 Chapter 15 Mechanisms of Cell Communication  Cells must communicate with one another  Cell to cell communication is more complex then sending a signal out and having a response  Extracellular signal molecules: communication between cells  Some operate over long distances and require other signaling molecules  Receptor molecules are present to help solve the distance issues  Intracellular signaling pathways: a molecule binds and causes more molecules to signal receiving cell targets  Target cells can affect effector proteins General principles of cell communication  Many bacteria are able to communicate through signaling  Yeast cells can also respond to each other sending out signals to indicate mating  Mating factors determine if the cell should divide  Yeast molecules have been studied for mutants function Extracellular signal molecules bind to specific receptors  Multicellular organisms have hundreds of types of signaling molecules  Most signal molecules exit through exocytosis and bind to receptors on molecules  Some signal molecules enter the cell through diffusion  Target cell always requires binding to a receptor Extracellular signal molecules can act over either short or long distances  Many signaling molecules involve binding directly to the surface  Contact-dependent signaling: important in development and immune responses o Can operate over large distances  Local mediators: secreted molecules can act over distances  Paracrine signaling: involve signaling molecules that are close together o Autocrine: cells that produce signals that they respond to o Paracrine signals act locally o They are taken up rapidly  Chemical synapses: signal transmission across long distances o Neurons are stimulated by responses through axons o Neuron sends an electrical response to the axon, the signal travels until a chemical signal neurotransmitter is activated and causes a response  Endocrine cells: signaling over long distances o Secreting signaling cells into the blood stream o Horomones  The speed of the signaling molecules depends on the mechanism of delivery and target cell’s response  Synthesis of a new protein takes longer then an already altered protein 884-886 (not figure 15-7) Gap Junctions allow Neighboring Cells to Share Signaling Information  Gap Junctions: narrow filled water channels that connect the cytoplasm of cells  These channels allow for the exchange of water, inorganic ions and other small water soluble molecules  Gap junctions provide cell communication  Gap junctions allow for symmetrical communication Each cell is programmed to Respond to Specific Combinations of Extracellular Signal Molecules  A cell must respond to specific signals  Different signals: survive, grow and divide, differentiate and die Different types of cells usually respond differently to the same extracellula
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