PHIS 206 1st Edition Lecture 3 Outline of Last Lecture Diffusion Osmosis and Transport I II III IV V VI VII Cell Physiology Organs Communication Methods Required Fluids How Solutes Behave Red Blood Cells Historical Background 17th Century How Do Large Molecules Get Across Outline of Current Lecture I Osmosis II Osmotic Pressure III Cell Membrane IV Active Transport Current Lecture I 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 freely II 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 O 2 molecules Doesn t matter if the mixture has tens of thousands of various molecules o only total matters not kinds Total pressure sum of all of the pressures Thermal agitation Ex tire air molecules push against wall of tire and cause exertion These 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 space o 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 apart IV 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 cell
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