BIOS 281 Lecture 3 Membrane Transport and Potentials

47 figure 4 8 facilitated diusion molecules can


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Unformatted text preview: Also known as carrier- mediated diﬀusion –  Speciﬁc protein carriers •  Unlike simple diﬀusion, facilitated diﬀusion can approach a maximum rate dependent upon the concentra0on of the diﬀusing substance Facilitated Diﬀusion Rate of diffusion is limited by Vmax of the carrier protein −  Units are pmol/min/mg −  So, adding more carriers should not affect Vmax Fig. 4.7 Figure 4-8 Facilitated Diﬀusion •  Molecules can either move based on charge or force Osmosis Osmosis occurs from pure water toward a water/salt solution. Water moves down its concn gradient. Figure 4-10 Fig. 4.9 Osmo0c pressure •  In ﬁgure on leR, if pressure were applied to the sodium chloride solu0on, osmosis would be slowed, stopped, or reversed •  The exact amount of pressure required to stop osmosis is called osmo0c pressure. •  Osmosis from B to A (water can move, red dots or solute can not) causes ﬂuid levels to change. –  Pressure diﬀerence becomes osmo0c pressure of that solu0on Diﬀerent compounds have diﬀerent osmolarity mOsm (millisomolar) or mOsm/L mM (millimolar) or mM/L = index of the concn of particles per liter soln = index of concn of molecules per liter soln 150 mM NaCl = 300 mOsm 300 mM glucose = 300 mOsm Who cares? •  You. There are normal levels of all compounds in our body which help to regulate water. •  Doctors can take blood (plasma) and look for various molecules to insure levels are within healthy ranges. –  Glucose, NaCl, Urea, etc Clinical abnormali0es of Fluid Volume Regula0on Hypernatremia (increased plasma Na+): •  Increased water loss •  Excessive sweat Loss •  Central or nephrogenic diabetes insipidus **decreased ADH secretion or responsiveness to ADH Hyponatremia (decreased plasma Na+): •  Large water ingestion •  Syndrome of Inappropriate ADH Secretion (SIADH) **too much ADH leads to water retention, hyponatremia, and excretio...
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This note was uploaded on 11/12/2013 for the course BIOS 281 taught by Professor Varamini during the Fall '12 term at Biola University.

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