BIOL 2021 Lecture Notes - Lecture 5: Passive Transport, Electrochemical Gradient, Cell Junction
9 Feb 2018
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Take a look at the info on moodle for nserc and the assignment instructions. Last time we talked about the active and passive transporters, today, we"re going to talk about channels which are always passive. Types of channels (611-613: gap junctions, also called porins, large pores, little selectivity, cell to cell junctions or organelle to cytosol. Epithelial cells of kidney or exocrine cells, where you need to excrete a lot of liquid. Water moves at a fairly slow rate: ion channels (613-614). Fig 11-21 ion channel, mechanism: transport inorganic ions and show ion selectivity. Ions pass through single file = selectivity filter: permitting some inorganic ions to pass, but not others. Gating of ion channels (614), fig 11-22: voltage gated: open when voltage across membrane changes, respond to voltage changes. Amino acid side groups will respond to voltage changes and lead to conformational changes: ligand gated: opens when a molecule binds.
