PHIS 206 1st EditionLecture 3Outline of Last Lecture Diffusion, Osmosis, and TransportI. Cell PhysiologyII. Organs― Communication Methods Required!III. FluidsIV. How Solutes BehaveV. Red Blood CellsVI. Historical Background: 17th CenturyVII. How Do Large Molecules Get Across?Outline of Current Lecture I. OsmosisII. Osmotic PressureIII. Cell MembraneIV. Active TransportCurrent LectureI. Osmosis-Water diffusing down its own gradient-Water’s diffusion rate is large b/c it is a small molecule (18.02 g/mol) diffuses freely and downhill-hydrostatic pressure: depends on height of column-Pressure pushes both ways, so result is equal counterparts-Membrane: water can cross easily, but water-soluble (big) molecules cannot cross freelyII. Osmotic Pressure: force exerted on water as it goes downhill-Van’t Hof: pressure exerted on molecules would be exactly the same as pressure exerted by any gas Every molecule of gas exerts the same pressure EX.) N v. O2 molecules Doesn’t matter if the mixture has tens of thousands of various moleculeso only total # matters, not kinds Total pressure= sum of all of the pressures Thermal agitationEx.) tire: air molecules push against wall of tire and cause exertionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Cell Membrane- Difference in different concentrations of molecules Actual concentration of biological fluids = 310 mM (millimols)- osmolarity (Osm): introduced to measure molarity of all osmotic substances if you change one side to 309 mOsm and the other to 310 mOsm:o Water will be lower on the 310 mOsm b/c it is more soluble and takes up more spaceo 15 mmHg will be pushing water if Na+ , then set up conditions to make water move with it*Osmosis is the only mechanism that deals with water in our bodies- Not actually molecules that diffuse through the membrane, atoms diffuse NaCl Na+ + Cl- osmotically independent osmolarity is 2 times the molarity: 1 for Na+ and 1 for Cl- - Less effect for large osmotically-active molecules, so molecules must break apartIV. Active Transport- Molecules move “uphill” (low to high concentrations) Requires Energy b/c molecules move in the opposite direction- ATP= ADP (basic subunit of biological systems) + P1 ( inorganic phosphate) + ENERGY- Active transport uses ATP to push molecules across- Membrane ATPase: sodium pumped out of cell, potassium pumped into cell- For stable K+ levels, the rate of diffusion = rate of pump pumping K+ into
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