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oct 30 mem2 - 10 How(through what part of the membrane do...

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1 How (through what part of the membrane) do these cross? O 2 , CO 2 glucose Na+ ion amino acid H+ ion water 10 Permeability of Phospholipid Bilayers HCO3- What factors determine the net direction of movement across a membrane? What factors affect the rate of movement of an anion (neg. chrg) across the membrane? PASSIVE TRANSPORT vs. ACTIVE TRANSPORT compare to Purves, Fig. 44.6 All living cells have an electrical potential ( = voltage) difference between the cytosol and the extracellular fluid. How can we measure membrane potential? What maintains the resting potential? Living cells have an electrical membrane potential that can be measured by inserting a fine glass microelectrode through the plasma membrane into the cytosol, and comparing the electrical potential (= voltage) inside the cell with that of the surrounding liquid medium. The cytosol is more negatively charged, although the magnitude of the potential differs for different types of cell. ! urves, Fig. 44.5 Certain cell types (nerve; muscle) produce electrical signals, i.e. rapid fluctuations in membrane potential that carry physiological information. Membrane potential = - 60 mV Electrical membrane signals occur in animals ... Action potential in nerve cell ... and plants: Electrical response to light stimulus in guard cell of a leaf Electrical signals across cell membranes result from the movement of mineral ions like Na + and Cl - . The polar H
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