BS 161 1st Edition Lecture 11 Outline of Last Lecture I Introduction to cell structure Outline of Current Lecture II More on cell structure Current Lecture Osmosis net diffusion of water net water movement across a membrane from high to low water concentration until it reaches equilibrium goes until isotonicity a water balance is achieved Hypotonic if the solute concentration is lower outside vs inside the cell water will rush in causes cell to swell burst Hypertonic if the solute concentration is higher outside vs inside the cell water will rush out causes cell to shrivel Isotonic if the solute concentration is the same outside and inside the cell there is no net water movement the cell is normal Facilitated diffusion impermeable weakly permeable molecules go from a high concentration to a low concentration through a transmembrane aka integral protein energy is not required ion channel proteins change conformation to move the ion Active transport change in the shape of transmembrane proteins using energy to transport molecules against a concentration gradient uses ATP hydrolosis to change transporter shape required for ion movement Membrane potential all cells generate one helps bring in cations and expel anions membrane proteins can change if their charge is made different can lose function Energy can be stored in an electric gradient of H Prokaryotic cells no nucleus DNA held in nucleoid no membrane bound organelles cytoplasm bound by the plasma membrane E coli has 5 x 106 base pairs circular Gram stain Positive is purple Negative is red Biodiversity more bacterial species being discovered due to advances in DNA sequencing and many species being unculturable
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