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Cell Communication Ch. 11 How are signals sent locally? • Cell Junctions: Animals and Plants pass molecules through the plasma membrane. • Cell-cell Recognition: Receptor sites on animal cells protrude from its surface and attach. – Composed of the glycocalyx. Also responsible for contact inhibition. • Paracrine Signaling: Local regulatory molecules are sent to neighboring target cells. • Synaptic signaling: neurotransmitters across the synapse. Membrane carbohydrates: Glycocalyx ( integral protein) • Play a key role in cell-cell recognition – ability of a cell to distinguish one cell from another • antigens – important in organ & tissue development – basis for rejection of foreign cells by immune system How are signals sent long distances? • Hormone Signaling: Endocrine systems sends signals through body fluids, often through the blood. – target cell : any cell that has a specific receptor for an antigen or antibody or hormone or drug, or is the focus of contact by a virus or phagocyte or nerve fiber etc. The Signal Transduction Pathway • Small number of extracellular signal molecules produce a major cellular response. Sutherland’s epinephrine STP • Three stages: – Reception: The protein binds to a cells surface receptor. This protein is often called a ligand. – Transduction: Signal molecule changes the receptor protein, the change is relayed to a secondary messenger. – Response: Secondary messenger induces the cellular response. G Protein Point of the two pathways? • Sutherlands Epinephrine pathway: epinephrine does not directly break down glycogen for fuel reserve. It does this through intermediate steps. • G Protein receptors – Used in yeast for mating, by hormones such as epinephrine, neurotransmitters, vision and smell. – G protein when active picks up GTP sends it to an enzyme and causes conformational shape which allows for the cellular response. – Botulism, cholera, pertussis (whooping cough) intefeer with the G-Protein funcion. – 60% of all medicines used today influce the G- protein pathway.
