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CellSignaling08Lec1 - All living cells have mechanisms that...

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All living cells have mechanisms that allow them to communicate. Cell signaling pathways. Signaling networks. Cell communication is mediated by EXTRACELLULAR SIGNALS.
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Cells Communicate in 3 ways. 1. Form Gap junctions: directly join the cytoplasms of interacting cells. Allow the exchange of small intracellular signaling molecules. 2. Secrete chemicals that signal neighboring or distant cells. 3. Display - plasma membrane bound signaling molecules. General Principles
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General Principles of Cell Communication Altered Metabolism Altered cell Shape or movement Altered Gene expression Metabolic enzyme Intracellular signaling proteins Activate Extracellular signal molecule Receptor Protein Target Proteins Gene regulatory protein Cytoskeletal protein Signal Transduction pathway
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Important differences between these signaling pathways. Endocrine pathway - signals are secreted. 1. Pathway relies on diffusion and blood flow. 2. Relatively slow signaling method. Long- lived signaling molecules. Signal -can be very selective . Each type of endocrine cell secretes different hormones. Target cells - have complementary receptors. Only cells with appropriate receptors will respond.
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Secretion of thyroid Hormone Nerve cell hypothalamus neuroendocrine cell Stimulate: specific neuroendocrine cells release TSH-releasing hormone (blood vessels of the Pituitary stalk). TSH-releasing hormone moves to the pituitary. Stimulates endocrine cells to produce TSH (Thyroid stimulating hormone). Pituitary Gland endocrine cell main bloodstream Thyroid Gland endocrine cell TSH is transported to the Thyroid. Endocrine cells are stimulated to produce Thyroid hormone. Thyroid hormone is small - hydrophobic Molecule. Can diffuse across PM and interact With Intracellular Receptors.
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Fast response - Paracrine or Synaptic Modes Fast response linked to the nervous system. Nerve cells - speed. Transmit signal via electrical impulses - only at nerve terminal is the electrical signal converted into a chemical signal. Paracrine mode - neurotransmitter functions as a local mediator. Diffuses outward - influences any target cells in the neighborhood. Synaptic mode - more precise signal. Effect on a single target cell. Signal - short lived, rapid turnover
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Two main classes of signaling molecules. 1) Lipophilic Hormones or very small signaling molecules. Can pass readily across the plasma membrane. 1) Signals that bind Cell-Surface receptors. **most signal molecules Hydrophilic and unable to cross the PM directly.
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hydrophobic Intracellular Receptor hydrophilic I. Lipophilic, small II. Hydrophilic Cell Surface Receptor
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15.2 Structure of steroid hormones, thyroid hormone, vitamin D 3 , and retinoic acid (Part 1) Examples: Signals that work with Intracellular Receptors
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Example : Small hydrophobic Signals that bind to receptors that are gene regulatory proteins.
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