Lab #5 pdf.pdf - Lab 5: Cell Membranes - Transport,...

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Lab 5: Cell Membranes - Transport, Diffusion, andOsmosisObjectives:1.Describe the structure and function of the cellular plasma membrane.2.Identify the cellular characteristics that are important in membrane transport.3.Summarize the importance of cellular membranes and transport in cells.4.Define the processes of diffusion and osmosis and contrast active versus passive transport.5.Describe the role of Brownian motion in diffusion and osmosis.6.Predict what will occur when animal cells are placed into solutions that are hypertonic,hypotonic, or isotonic.7.Predict what will occur when cells with walls are placed into solutions that are hypertonic,hypotonic, or isotonic.8.Explain the effects of molecular weight on diffusion rate.Vocabulary:semi-permeable, active processes, active transport, bulk transport, passive processes, kineticenergy, Brownian motion, simple diffusion, concentration gradient, solvent, solute, phospholipidbilayer, equilibrium, solution, facilitated diffusion, osmosis, osmotically active substances, osmoticpressure, osmotic concentration, tonicity, isotonic, hypertonic, crenation, hypotonic, lysis, turgid,plasmolysis.Introduction:The ability of the cell membrane to separate the internal cellular environment from the externalenvironment is essential to cell survival. The cell membrane is the gatekeeper, regulating the flowof substances in and out of the cell. This membrane issemi-permeable; some substances can passthrough but others cannot. There are many mechanisms that allow for the passage of substancesacross the cell membrane. They are categorized based on the source of the energy used.Activeprocessesutilize cellular energy, usually ATP (adenosine triphosphate), and have the ability tomove a substance against its concentration gradient.Active transportandbulk transportareprocesses requiring cellular energy that will be discussed in lecture. Today’s lab will focus onpassive processeswhich do not use cellular energy. Instead the energy that drives the movementof the substances is thekinetic energyof molecules. The atoms or molecules that make up a liquidor a gas are in constant thermal motion. The temperature of the fluid determines the velocity ofthese atoms or molecules. As a result of the motion of the molecules, neighboring molecules arehit at random. The impact makes the molecules move. This movement is calledBrownian motion(quick video)and is defined as the random and constant movement of tiny particles when they aresuspended in a fluid or gas. This motion is the result of invisible atoms in the fluid bumping thesuspended particles and making them jiggle.There are several different passive processes powered by Brownian motion that are responsible forthe movement of materials across the cell membrane. We will discuss three of these;simplediffusion, facilitated diffusion,andosmosis.Simple diffusionis the net movement of a substance from an area where that substance is in high

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Term
Winter
Professor
P. Pepe

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