LessonNo3GeneTonicityFall2010

LessonNo3GeneTonicityFall2010 - Physiology BIO 240 Lecture...

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Click to edit Master subtitle style Physiology BIO 240 Lecture No. 3 Tonicity Genetics Fall 2010 Dr. Ana M Jimenez
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Click to edit Master subtitle style Membrane Transport Passive and Active Transport, osmosis, tonicity
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Thinking About Cell Membranes Most of the cell membrane is made of phospholipids, Cell membranes are hydrophobic , How do hydrophilic molecules such as water cross the membrane? What forces water to move across the cell membrane?
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Membrane Transport Cells have a selectively permeable membrane Allow some but NOT other molecules to go through, Factors : size, charge, polarity, hydrophilic/hydrophobic Passive Movement : does not require cell to spend energy (ATP), Simple Diffusion Facilitated Diffusion Filtration Active Movement : requires cell to spend cellular energy (ATP) Active Transport
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Simple Diffusion Movement of particles from an area of HIGH concentration to an area of LOW concentration ([]=concentration), [High] ° [Low] Concentration gradient - difference between area of [high] and area of [low]
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Factors that Affect Diffusion Rate Temperature : Higher temperature, faster rate. Molecular weight : Higher molecular weight, slower rate. ‘Steepness of concentration gradient : Larger difference between concentrations, faster rate. Membrane surface area : Larger surface area, faster rate. Membrane permeability : Increased permeability, faster rate.
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Filtration vs. Osmosis of Fluid Filtration - hydrostatic (water) pressure Forces water to go through a filter, Kidney filtration is important in removing waste from the blood, Filtration of fluid at capillaries is governed by Starling Law of capillary diffusion. Osmosis – tonicity (solute) pressure Forces water to go through a membrane, Water does not cross plasma membrane easily, but crosses through water pores called aquaporins .
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Facilitated Diffusion Carrier or pore - mediated transport DOES NOT require energy, Cells transport hydrophilic molecules that would not go through the membrane such as glucose or water, Specific for each molecule, transport is dependent on solute concentration: Large concentration gradient = faster rate Small concentration gradient = slower rate Some carriers glucose – saturate (glucose)
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High [molecule] Low [molecule]
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Osmosis Only molecules that cannot cross plasma membrane determine ‘tonicity’, Tonicity – force of solutes that moves water across a membrane, Large particles (albumin) cannot move through the membrane, No transporters for proteins only for amino acids. Small particles and water, glucose can move through membrane due to transporters found on membrane (Ex. Aquaporins, glucose transporter - GLUT)
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Side A = 5% albumin, Side B = 10% albumin Side A has a LOW [albumin] as compared to side B, Albumin can NOT move through the membrane, In order for albumin to reach equilibrium , water is forced to move from side A into side B, At equilibrium, albumin concentration is the same on both sides, water has moved from A to B (not albumin), A B A B
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Osmolarity vs. Tonicity
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