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IV. Cell Signaling Chapter 11 AP Biology External Signals are converted into resonses within the cell Animal cell communication a. Direct Contact b. Long Distance Signaling c. Local regulators AP Biology growth factors, neurotransmitters Fig. 11-5 Long-distance signaling Local signaling Electrical signal along nerve cell triggers release of neurotransmitter Target cell Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling Endocrine cell Neurotransmitter diffuses across synapse Secretory vesicle Target cell is stimulated Blood vessel Hormone travels in bloodstream to target cells Target cell (b) Synaptic signaling (c) Hormonal signaling AP Biology 3 Stages of cell signaling 1. Reception – binding between signal molecule (ligand) and a receptor Highly specific Causes conformational change of receptor (usually a protein) Example: G-proteinlinked receptor works with help of cytoplasmic G Protein. Tyrosine kinases are then activated and add phosphate to tyrosines on the cytoplasmic side AP Biology Fig. 11-7b Plasma membrane G protein-coupled receptor Inactive enzyme Activated receptor Signaling molecule Inactive enzyme GDP CYTOPLASM GDP Enzyme G protein (inactive) 2 1 GTP GTP replaces GDP when protein is activated by the receptors conformational change Activated enzyme Inactive enzyme GTP GDP Pi Cellular response 3 G protein then activates an enzyme by causing a conformational change. Enzyme can now trigger next step in pathway AP Biology 4 G Protein hydrolyzed GTP to make GDP = Inactive G protein and Enzyme Example 2: Ligand gated ion channel signal molecule binds to receptor (protein channel) and causes a conformational change that opens the channel AP Biology Fig. 11-6-1 EXTRACELLULAR FLUID 1 Reception Receptor Signaling molecule AP Biology CYTOPLASM Plasma membrane 2. Transduction Signal is turned into a different form (usually, conformational change in a protein) Most include phosphorylation cascades Each molecule adding a phosphate group on to the next molecule AP Biology Fig. 11-6-2 CYTOPLASM EXTRACELLULAR FLUID Plasma membrane 1 Reception 2 Transduction Receptor Relay molecules in a signal transduction pathway Signaling molecule AP Biology 3. regulation of enzyme activity cytoskeleton rearrangement activate transcription factors (proteins that turn on and off genes) Each signal amplifies by activiting multiple copies of the next component of the pathway. AP Biology Fig. 11-6-3 CYTOPLASM EXTRACELLULAR FLUID Plasma membrane 1 Reception 2 Transduction 3 Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signaling molecule AP Biology Fig. 11-9 Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP ADP Pi P Active protein kinase 2 PP Inactive protein kinase 3 Pi ATP ADP Active protein kinase 3 PP Inactive protein P ATP P ADP AP Biology Pi PP Active protein Cellular response