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Lab 3Nur 0002Lab 3- Membrane Transport I.Membrane Transport Lab A.Movements Through The Plasma MembraneThe plasma membrane is selectively permeable based on polarity, allowing only certain substances to pass through it. The internal environment is different from the external environment and selective transport helps to maintain these differences.Substances move across the membrane in 3 ways:Directly through the lipid bilayer by diffusion or osmosis. (small, nonpolar, lipid based)Through membrane channels (facilitated diffusion and active transport) (larger, charged, glucose)In vesicles (Endocytosis and Exocytosis) B.Diffusion Diffusion is the tendency of solute particles to move from an area of higher concentration within a solution to an area of lower concentration.Diffusion is due to random molecular motion of molecules (Brownian motion).Low molecular weight, small molecules, high temp, large amounts of molecules makes diffusion happen fasterDiffusion is a passive process, meaning it requires no energy expenditure by the cell (compare to active transport).Most solutions are either a liquid or a gas and consist of a solvent with solutes dissolved in it.Equilibriumis when there is no net movement of solutes within the solution.Main extracellular electrolyte is Na, too much, water will diffuse out of cells to balance it outC.OsmosisIt is the diffusion of water (solvent) across a selectively permeable membrane.Water moves easily into and out of cells.Water tends to move across from an area where there is more water (more water=less solutes), to an area where there is less water (less water=more solutes)Osmotic pressure- If there is a solution which is very concentrated with solutes, water will tend to move into it more strongly than into a weaker solution. This tendency of water to move into a solution is known as osmotic pressure).Factors Affecting Diffusion and Osmosis Rates1.Concentration gradient- larger is faster, less distance = greater the gradient. Large gradient means larger osmotic pressure.2.Temperature- as temperature rises particles move faster and rate increases.3.Size of molecules- smaller molecules diffuse more readily than do larger ones.4.Surface area of membrane– greater surface area = more diffusion.D.Hypotonic, Isotonic and Hypertonic solutions 1
Lab 3Nur 0002The movement of water across the cell membrane is of utmost importance to all thecells in the body because it can affect cell volume, cell shape and ultimately, cell survival. Solutions can be described using terms that describe the solute concentration of the solutions relative to the solute concentration inside our cells. You should recall that normally the salinity inside most cells and in the extracellular fluid is about .9%NaClCells have a tendency to shrink or swell when placed in solution. On the following page you will have the chance to sketch out what happens to cells when they are placed in each type of solution.
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Osmosis, Semipermeable membrane, bag, Membrane Transport Lab