lecture_notes_03_(ta) - Lecture 3: Membrane Transport...

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Lecture 3: Membrane Transport Reading: chapter 3, section: membrane transport, pgs 57-70 (pgs 53-64, if using 3 rd edition) (TA NOTES IN RED . P LEASE NOTE THAT I AM USING AN OLD VERSION OF THE LECTURE NOTES . FIGURE AND PAGE NUMBERS REFER TO THE FIFTH E DITION OF OUR TEXT …) Intercellular Communication Gap junctions ( CYTOPLASM IS CONTIGUOUS ) Communicating junctions that permit the passage of small molecules ( AND IONS ) Direct signaling ( CELLS BIND TOGETHER , BUT CYTOPLASM IS NOT CONTIGUOUS ) Extracellular protein-protein interactions Extracellular chemical messengers (Figure 3-7) paracrine ( LOCAL , NO ELECTRICAL SIGNAL INVOLVED ) hormone ( GLOBAL , THROUGH BLOODSTREAM , NO ELECTRICAL SIGNAL INVOLVED ) neurotransmitter ( LOCAL , ELECTRICAL SIGNAL INVOLVED ) neurohormone ( GLOBAL , ELECTRICAL SIGNAL INVOLVED ) How are extracellular chemicals secreted by one cell detected by another? 1. G protein coupled receptors, coupled to 2nd messengers pathways e.g. cAMP, IP3 pathways These pathways ultimately bring about a cellular response by altering the structure and function of proteins. ( DO NOT HAVE BUILT - IN ION CHANNEL PORE ) 2.  Activation of ion channels Ion channels are membrane proteins that permit small soluble ions such as Na, K, Ca and Cl to pass across the plasma membrane. There are two major types: leak channels, which are always open, and gated channels, which open and close in response to various stimuli. Different types of gated channels are gated by changes in membrane voltage, mechanical deformation,or binding of chemical messengers. For the latter category, there are two types: Ionotropic signaling Activation of ion channels by direct binding of extracellular chemical messenger ( RECEPTOR + PORE PROTEIN COMPLEX ) Metabotropic signaling Activation of ion channel via 2
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lecture_notes_03_(ta) - Lecture 3: Membrane Transport...

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