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Membran sel dan transport. Agustina Setiawati , M.Sc., Apt. Model membran. - PowerPoint PPT Presentation

Text of Membran sel dan transport

Membran sel dan transport

Membran sel dan transportAgustina Setiawati, M.Sc., Apt

1Model membranFluid Mosaic Model 1972 Singer & Nicolson : lipid diatur dlm struktur 2 lapis dg protein yg berbeda2 tertanam / menempel pada lipid (mosaik), dimana protein & fosfolipid dpt bergerak bebas pada membran (fluid).2Fluid Mosaic Membrane

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10Protein membran. cont.

Text pg 8011Protein membran integral12Protein membran peripheralIntegral13Membrane ProteinsProteins determine membranes specific functionscell membrane & organelle membranes each have unique collections of proteinsMembrane proteins:peripheral proteins loosely bound to surface of membranecell surface identity marker (antigens)integral proteins penetrate lipid bilayer, usually across whole membrane transmembrane proteintransport proteinschannels, permeases (pumps)


Why areproteins the perfect molecule to build structures in the cell membrane?15Classes of amino acids

What do these amino acids have in common?nonpolar & hydrophobic16Classes of amino acids

What do these amino acids have in common?polar & hydrophilic

I like thepolar onesthe best! 17Proteins domains anchor moleculeWithin membranenonpolar amino acids hydrophobic anchors protein into membraneOn outer surfaces of membranepolar amino acids hydrophilicextend into extracellular fluid & into cytosol

Polar areasof proteinNonpolar areas of protein18

Many Functions of Membrane ProteinsOutsidePlasmamembraneInsideTransporterCell surfacereceptorEnzymeactivityCell surface identity markerAttachment to thecytoskeletonCell adhesion19Signal transduction - transmitting a signal from outside the cell to the cell nucleus, like receiving a hormone which triggers a receptor on the inside of the cell that then signals to the nucleus that a protein must be made.Membrane carbohydrates Play a key role in cell-cell recognitionability of a cell to distinguish one cell from anotherantigensimportant in organ & tissue developmentbasis for rejection of foreign cells by immune system

20The four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells.SIFAT MEMBRAN SEL TERHADAP MOLEKUL

21Types of Cellular TransportPassive Transport cell doesnt use energyDiffusionFacilitated DiffusionOsmosis

Active Transportcell does use energyProtein PumpsEndocytosisExocytosishighlowThis is gonna be hard work!!highlowWeeee!!!22Passive Transportcell uses no energy molecules move randomlyMolecules spread out from an area of high concentration to an area of low concentration. (HighLow)

233 Types of Passive TransportDiffusion Facilitative Diffusion diffusion with the help of transport proteins Osmosis diffusion of water


1. DiffusionDiffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low)Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. Biology, Cell membranes and Transport26What determines the rate of diffusion?There 4 factors:Gradien konsentrasiMakin besar gradien konsentrasi semakin cepat difusi2. Suhumakin tinggi suhu, makin tinggi energi kinetik molekul sehingga probabilitas difusi lebih besar3. Luas permukaan difusimakin luas permukaan difusi semakin banyak molekul yg berdifusi4. Tipe molekul/ion yang berdifusiMolekul yang lebih besar lebih sulit berdifusiMolekul non polar/hidrofobik lebih mudah berdifusi karena larut dalam ekor non polar fosfolipid.

26AS Biology, Cell membranes and Transport27Molecules that diffuse through cell membranesOxygen Non-polar so diffuses very quickly.

Carbon dioxide Polar but very small so diffuses quickly.

Water Polar but also very small so diffuses quickly.

272. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane Transport Proteins are specific they select only certain molecules to cross the membraneTransports larger or charged molecules

Facilitated diffusion (Channel Protein)Diffusion (Lipid Bilayer)

2. Facilitated Diffusion

Carrier ProteinAB

High ConcentrationLow ConcentrationCell MembraneGlucosemoleculesProteinchannel2. Facilitated DiffusionGo to Section:Transport ProteinThrough a Cellular Transport From a-HighLow29Transpoter glukosa (GluT)

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31How to get other molecules across membranes??Transport proteins Transports molecules or ions across biological membranes3 types of transport proteins:1.uniport



32Uniport Transport Protein extracellularfluidintracellularfluidCarries a single solute across the membrane.33Symport Transport ProteinTranslocate 2 different solutes simultaneously in same direction.

intracellularfluidextracellularfluid34Antiport Transport ProteinExchanges 2 solutes by transporting them in opposite directions.

intracellularfluidextracellularfluid35AS Biology, Cell membranes and Transport36

36AS Biology, Cell membranes and Transport37Facilitated Diffusion through a membraneCell membraneInside cellOutside cellProtein channel37AS Biology, Cell membranes and Transport38Facilitated Diffusion through a membraneCell membraneInside cellOutside cellProtein channeldiffusion38AS Biology, Cell membranes and Transport39Facilitated Diffusion through a membraneCell membraneInside cellOutside cellProtein channeldiffusionEQUILIBRIUM393.Osmosis: diffusion of water through a selectively permeable membraneWater moves from high to low concentrations

Water moves freely through pores.Solute (green) to large to move across.Osmosis animationPassive Transport: 3. Osmosis40Effects of Osmosis on Life

Osmosis- diffusion of water through a selectively permeable membrane

Water is so small and there is so much of it the cell cant control its movement through the cell membrane.

41Hypotonic Solution

Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

42Hypertonic SolutionHypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

shrinks43Isotonic SolutionIsotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)


What type of solution are these cells in?ACBHypertonicIsotonicHypotonic45Sel tumbuhanFirmness or tension (vacuole full) that is found in plant cells (cell wall) that are in a hypotonic environment is called TURGID.This process is called TURGOR PRESSURE.

WaterCentralVacuoleWaterWaterWater46When the plasma membrane pulls away from the cell wall (vacuole empty) in a hypertonic environment (loss of water) is called PLASMOLYSIS

WaterWaterCellWallWaterplasma membrane47How Organisms Deal with Osmotic PressureBacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.Salt water fish pump salt out of their specialized gills so they do not dehydrate.Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.48Active Transportcell uses energy actively moves molecules to where they are neededMovement from an area of low concentration to an area of high concentration (Low High)

49Types of Active Transport1. Protein Pumps -transport proteins that require energy to do workExample: Sodium / Potassium Pumps are important in nerve responses.

Protein changes shape to move molecules: this requires energy!50

Active transport in two solutes across a membraneFigure 5.18Transportprotein1FLUIDOUTSIDECELLFirstsoluteFirst solute, inside cell, binds to proteinPhosphorylated transport protein2ATP transfers phosphate to protein3Protein releases solute outside cell4Second solute binds to proteinSecond solute5Phosphate detaches from protein6Protein releases second solute into cell51Contoh pompa protein transport aktif

52Resistensi sel kanker terhadap beberapa obat sitotoksikContoh pompa protein transport aktif


54Types of Active Transport2. Endocytosis: taking bulky material into a cell Uses energyCell membrane in-folds around food particlecell eatingforms food vacuole & digests foodThis is how white blood cells eat bacteria!

55EndocytosisTransports macromolecules and large particles into the cell.

Part of the membrane engulfs the particle and folds inward to bud off.

The energy requiring movement of particles (foreign or natural) into the cell.

3 types of endocytosis:A.PhagocytosisB.PinocytosisC.Receptor-mediated endocytosis

56A. PhagocytosisCell eating: cells engulf particles with pseudopodia and pinches off a food vacuole.

Two examples:1.White Blood Cell2.Amoeba

FoodVacuoleWhite Blood CellBacteria57Phagocytosis. cont.Invagination of membrane surrounding the particles.depression then pinched off to form phagocytic vacuole. Lysosomes release their enzymes Useful products are absorbed and undigested matter is expelled by exocytosis.

58B. PinocytosisCell drinking: droplets of extracellular fluid are absorbed into the cell by small vesicles.


Food ParticlesHyphae59Pinocytosis.... cont.

60C. Receptor-Mediated EndocytosisImporting specific macromolecules (hormones) into the cell by the inward budding of vesicles formed from coated pits (receptors).

HormonesReceptorsLiver Cell61

Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors62Types of Active Transport3. Exocytosis: Forces material out of cell in bulkmembrane surrounding the material fuses with cell membraneCell changes shape requires energyEX: Hormones or wastes released from cell

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66Want to know more? Just ask!