Cell Structure & Function

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Cell Structure & Function. Structure & Movement Through Membranes (There and Back Again). The Cell Membrane. Key Concept: The cell membrane regulates what enters and leaves the cell and also provides protection and support. The Cell Membrane. - PowerPoint PPT Presentation

Transcript of Cell Structure & Function

  • Cell Structure & FunctionStructure & Movement Through Membranes(There and Back Again)

  • The Cell MembraneKey Concept:The cell membrane regulates what enters and leaves the cell and also provides protection and support

  • The Cell MembraneThe cell takes in nutrients and expels wastes plus cell products through the cell membraneThe Basic Structure Of Nearly All Cell Membranes Is The LIPID BILAYER

  • LIPID BILAYERSForm Automatically When Certain Lipids Are Dissolved In WaterTough Flexible StructureStrong Barrier Between Cell Contents And Its Surroundings

  • LIPID BILAYERS

  • LIPID BILAYERS

  • Fluid Mosaic ModelIn Addition To The Bilayer, The Cell Membrane Contains:

    Proteins That FormChannels & Pumps

    Proteins with Carbohydrates That FormAntigenic SitesCommunication Sites

  • DiffusionAll Living Cells Contain And Are Surrounded By Liquid.THE CELL MEMBRANE REGULATES THE MOVEMENT OF MOLECULES FROM ONE SIDE OF THE MEMBRANE TO THE OTHER

  • CytoplasmIs A Solution Of Many Different Substances In Water

  • SolutionA liquid mixture of 2 or more substances evenly mixed.SolventThe liquid in which the substances are mixedSoluteSubstances dissolved in the Solvent

  • Concentration Of SolutionConcentration = Mass of the solute in a given volume of solvent.Mass/Volume e.g.

    12g of NaCl dissolved in 3L H2Oequals12g/3L or 4.0 g/L

  • In A SolutionMolecules Are Moving Constantly They Collide and Bounce off each otherThis causes them to spread out randomly

    Resulting In:Movement from: an area of higher concentration to an area of lower concentration This process is called: Diffusion

  • DIFFUSIONMolecules move away from an area of Higher Concentration to areas of Lower ConcentrationEquilibriumConcentration of a solute is the same throughout the solutionThe concentration is the same EVERYWHERE

  • Diffusion

  • DIFFUSIONKey Concept: Diffusion Causes Many Substances To Move Across A Cell Membrane But:Diffusion Does NOT Require The CellTo Use Energy It just happens naturally!

  • Diffusion & CellsSubstances that can diffuse across cell membranes will do so until equilibrium is reachedDiffusioncontinues after equilibrium but the rates are equal in ALL Directions Atoms & Molecules Never Stop Moving

  • OSMOSIS

  • Osmosis Requires A MembranePermeable MembraneSubstance Can Easily CrossImpermeable MembraneSubstance Can NOT CrossSelectively Permeable Membrane aka = Semipermeable MembraneSome Substances Can Cross, Others Can NotCell Membranes are Semipermeable

  • OSMOSISKey Concept:Osmosis = The Diffusion Of Water Through A Selectively Permeable Membrane

  • The TonicsHypotonicLess concentrated solutionIsotonicEqually concentrated solutionHypertonicMore Highly concentrated solution

  • The Tonics

  • The Tonics

  • How Osmosis WorksOverhead Sugar & WaterMembrane Impermeable To SugarWater moves from a higher concentration of WATER to a lower concentration of WATER (NOT Sugar)

  • Osmotic PressurePressure exerted on the hypertonic side of a selectively permeable membraneMay cause cells to shrink or burst

  • Osmotic PressureCell MembraneContractile Vacuoles

  • Facilitated DiffusionMolecules that can easily diffuse across the cell membrane:AlcoholWaterSmall Lipids

  • Facilitated DiffusionOther molecules can not pass through the cell membrane but still get into the cell.

    HOW?

  • Facilitated DiffusionThru Protein Channels in the Cell Membrane that allow a substance to cross.Allows Diffusion In Both DirectionsEach Channel Substance SpecificDOES NOT REQUIRE ENERGY

  • Facilitated DiffusionProtein Channel Is Substrate SpecificSubstrate Can Move Either Direction Depending On Concentration. Always from area of Higher Concentration to area of Lower Concentration!

  • Active TransportMoves Material Across A Cell Membrane

    Against A Concentration Gradient

    (from area of Lower concentration into an area of Higher concentration)

  • Active TransportRequires Energy

  • Energy Molecule

  • Active Transport

  • Active TransportEndocytosisUsed to bring in large molecules, food, and whole cellsExocytosisMembrane surrounded material from inside the cell fuses with the cell membrane, releasing the contents.

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