2018 Membrane Transport 2.ppt

2018 Membrane Transport 2.ppt - 91703 Physiological Systems...

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91703 Physiological Systems Membrane Transport
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Diffusion 2nd Law of Thermodynamics Governs biological systems universe tends towards disorder (entropy) Diffusion movement from high low concentration Diffusion movement from high low concentration
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DIFFUSION
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Passive Transport Processes Diffusion – movement of solute molecules from high to low concentration i.e. moving down or with its concentration gradient until equilibrium is reached
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Diffusion Rates Factors affecting diffusion rate through a membrane Temperature - temp., motion of particles Size (molecular weight) - larger molecules move slower Steepness of concentrated gradient - difference, rate Membrane surface area - area, rate Membrane permeability - permeability, rate – dependent on molecule’s lipid solubility, molecule’s size, lipid composition of membrane Diffusion distance Electrical potential (diffusing ions which have a charge on them) Pressure differences e.g. blood gases
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Ficks Law Diffusion rate ~ Concentration gradient x membrane permeability surface area Flux ~ Concentration gradient x membrane permeability Rate of diffusion ~ SA x Concentration gradient x membrane permeability Membrane thickness Flux is defined as flow per unit area, where flow is the movement of some quantity per time Membrane thickness Membrane thickness Membrane permeability ~ lipid solubility molecular size
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1. Less wall thickness 2. Small MW molecules 3. Increase concentration difference Amount of particles time 4. Increased area V = (C 1 – C 2 ) x A x D T V = (C1 – C2) x D T A Flux Gradient Diffusion Coefficient Amount of particles time
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Ficks Law Diffusion rate ~ Concentration difference x membrane permeability surface area Flux = Gradient x Diffusion coefficient Rate of diffusion ~ SA x Concentration difference x membrane permeability Membrane thickness Flux is defined as flow per unit area, where flow is the movement of some quantity per time Membrane thickness Membrane permeability ~ lipid solubility molecular size = Diffusion coefficient
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Fick’s Law Diffusion is of a substance is from an area of high concentration to an area of low concentration. Diffusion can be represented by a basic equation often referred to as Fick’s law. J = -D*∆C/∆x J is the flux and describes the movement of a substance from one point to another in a given time. The units are moles/(area*time). D is the diffusivity coefficient which is a constant which describes how fast or slow a substance diffuses. It is dependent on temperature, viscosity and particle size. The units are area/time (cm 2 /sec) ∆C is the change in concentration (mol/cm 3 ) ∆x is the change in distance which the diffusing substance has travelled (cm)
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