Bio notes ch 12 - =General signal transduction pathway A....

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=General signal transduction pathway A. Reception a. The signal ligand binds to the receptor protein and changes its shape. III Three families of Plasma Membrane Receptors A. G- protein receptors a. Yeast mating, epinephrine receptors and some neurotransmitters use G proteins b. G stands for Guanine triphosphate activated protein c. See fig. 11.7 i. See g-proteins in Blood vessel growth ii. Development (embryonic) vision and smell iii. Cholera, botulism, pertussis 1. Bacterial 2. Rosine-Toxins that interfere with G proteins B. Tyrosine-kinase receptors a. Often receptors for growth factors b. Signal more than one pathway at once c. Undergo auto-phosphorylation i. Catalyze the transfer of a phosphate from ATP to tyrosine d. abnormal tyrosine-kinase receptors that aggregate without a signal can lead to cancer. C. C.Ion Channel Receptors or Ligand gated ion channels a. Ligand binding causes protein pores to open allowing or blocking the flow of ions b. E.g. Neurotransmitter acetylcholine open sodium channels causing depolarization of the neuron IV.Intracellular Receptors Receptors located in the cytoplasm or nucleus of target cells Signal ligand must be able to pass through the plasma membrane
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Cholestrol based hormones can get across membranes really easily. Can get into every cell. E.g. Sterod and thyroid hormones Receptors in the cytosol which can bind to and turn on genes in the nucleus Reception has carried out the complete transduction of the signal by acting as a transcription pathway and producing a protein. V. Signal Transduction Pathways A. General a. External signal -> internal effect b. External ligan binds to a plasma membrane protein c. Activates -> perhaps a G protein d. Activates or produces a second messenger e. Activates protein kinases f. Activates target enzyme allows the response to be large B. Phophorylate substrate proteins on either seranine or threonine(amino acids) a. Conformational change i. Can result in an active enzyme b. Protein kinases can act on each other and cause signal amplification c. each cell has 100’s of kinds of different protein kinases ~ 1% of our genes code for kinases. d. Regulates i. Cell production e. linked to cancer f. protein phosphatases remove the phosphate from the first signal – turns off the system (pg 221) C. Second Messengers a. Non protein, small, water soluble b. Easily diffuse through the cytosol c. Ca 2+ , cyclic AMP d. G-proteins adrenak cyclase which converst ATP cyclic AMP activates protein kinases
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e. Ca2+ - muscle contraction released from endoplasmic reticulum in response to a nerve impulse. Ca 2+ can activate kinases. VI. Cellular Responses VII. Apoptosis A. General a. integrates multiple cell-signaling pathways b. Apoptosis is programmed or controlled cell suicide c. A cell is chopped and packaged into vesicles that are digested by scavenger cells d. Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells B. Apoptosis during development
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This note was uploaded on 11/22/2009 for the course SCIENCE 100923 taught by Professor Gryphon during the Spring '09 term at University of the Fraser Valley.

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Bio notes ch 12 - =General signal transduction pathway A....

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