Membrane
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Transcript of Membrane
PLASMA MEMBRANEPLASMA MEMBRANE
Plasma Membrane
• Boundary that separates the living cellliving cell from it’s nonnon--livingliving surroundings.
•• Phospholipid bilayerPhospholipid bilayer•• AmphipathicAmphipathic - having both:
hydrophilic headshydrophobic tails
• ~8 nm thickPhospholipidPhospholipid
Plasma Membrane Plasma Membrane -- cont.cont.
•• Controls trafficControls traffic into and out of the cell with phospholipidsphospholipids and and transport proteinstransport proteins..
•• Selectively permeableSelectively permeable
Transport proteinTransport protein
Selective PermeabilitySelective Permeability
• The propertyproperty of biological membranesbiological membraneswhich allows some substances to cross more easily than others.
Fluid MosaicFluid Mosaic
• 1972 - SingerSinger and NicolsonNicolson called the membrane a “Fluid Mosaic Model”.
•• Mosaic:Mosaic: different proteins embedded in the phospholipids.
•• Fluid:Fluid: proteins and phospholipids can move freely in the membrane.
Fluid Mosaic Fluid Mosaic -- cont.cont.
• Components of a phospholipid bilayer.1.1. phospholipidsphospholipids2.2. proteins proteins -- enzymes, receptors, transport.enzymes, receptors, transport.3.3. glycolipidsglycolipids4.4. glycoproteinsglycoproteins5.5. carbohydratescarbohydrates6.6. cholesterolcholesterol
Transport ProteinsTransport Proteins
•• TransportsTransports moleculesmolecules or ionsions across biological membranes
•• 3 types of transport proteins3 types of transport proteins:11. uniportuniport
22. symportsymport
33. antiportantiport
Uniport Transport ProteinUniport Transport Protein
• Carries a single solutesingle solute across the membrane.
extracellularfluid
intracellularfluid
Symport Transport ProteinSymport Transport Protein
•• Translocate 2 different solutesTranslocate 2 different solutes simultaneously in same direction.
intracellularfluid
extracellularfluid
Antiport Transport ProteinAntiport Transport Protein
•• Exchanges 2 solutesExchanges 2 solutes by transporting them in opposite directionsopposite directions.
intracellularfluid
extracellularfluid
DiffusionDiffusion
• The net movement of a substance (molecules)down a concentrationconcentration gradientgradient from an area of highhigh concentrationconcentration to an area of lowlowconcentrationconcentration.
•• passive transport:passive transport: NONO energyenergy is expended.
•• facilitated diffusion: facilitated diffusion: type of passive transportpassive transportwhich uses transport proteins.transport proteins.
OsmosisOsmosis
• The movement of waterwater across selectively selectively permeable membranespermeable membranes.
• The waterwater moves from a high concentrationhigh concentrationto low concentrationlow concentration.
Question:Question:WhatWhat’’s in a Solution?s in a Solution?
Answer:Answer:
•• solutesolute + solventsolvent → solutionsolution
•• NaClNaCl + HH2200 → saltwatersaltwater
HypertonicHypertonic
• A solutionsolution with a greater solutegreater soluteconcentrationconcentration compared to another solutionsolution.
3% NaCl97% H2O
Red Blood Cell
5% NaCl95% H2O
solutionsolution
HypotonicHypotonic
• A solutionsolution with a lower solute concentrationlower solute concentrationcompared to another solutionsolution.
3% Na97% H2O
Red Blood Cell
1% Na99% H2O
solutionsolution
IsotonicIsotonic
• A solutionsolution with an equal solute concentrationequal solute concentrationcompared to another solutionsolution.
3% Na97% H2O
Red Blood Cell
3% Na97% H2O
solutionsolution
Movement of HMovement of H22OO
• Water will ““ALWAYSALWAYS”” diffuses down a concentration gradient from a HYPOTONICHYPOTONICsolutionsolution to a HYPERTONICHYPERTONIC solutionsolution.
““ALWAYS REMEMBERALWAYS REMEMBER””•• HYPOTONICHYPOTONIC →→ HYPERTONICHYPERTONIC
Animal CellsAnimal Cells•• Animal cellsAnimal cells placed into a hypotonic solution
will HEMOLYSIS (EXPLODE).HEMOLYSIS (EXPLODE).•• Animal cellsAnimal cells placed into a hypertonic solutionhypertonic solution
will CRENATE (SHRIVEL).CRENATE (SHRIVEL).
HemolysisCrenation
RedRedBloodBloodCellsCells
Plant CellsPlant Cells• Firmness or tension (vacuole full)(vacuole full) that is found
in plant cells (cell wall) that are in a hypotonic environment is called TURGIDTURGID..
• This process is called TURGOR PRESSURE.TURGOR PRESSURE.
WaterWater
CellWall Water
CentralVacuole
Plant CellsPlant Cells• When the plasma membraneplasma membrane pulls away from
the cell wallcell wall (vacuole empty)(vacuole empty) in a hypertonic hypertonic environmentenvironment (loss of water)(loss of water) is called PLASMOLYSISPLASMOLYSIS.
Water Water
CellWall Water
plasma membraneplasma membrane
Active TransportActive Transport
• The movement of moleculesmovement of molecules (small or large) across the plasma membraneplasma membrane in which energy energy (ATP)(ATP) is requiredrequired.
•• Examples:Examples:
1.1. Sodium (Na) Sodium (Na) -- Potassium (K) PumpPotassium (K) Pump2.2. ExocytosisExocytosis3.3. EndocytosisEndocytosis
Sodium-Potassium Pump
• The mechanism that uses energy (active transport)energy (active transport)released from splitting ATPsplitting ATP to transport Sodium Sodium (Na(Na++)) out out of and Potassium (KPotassium (K++) into cells. ) into cells.
extracellularfluid
intracellularfluid
Na+ Na+
K+ K+
Question:Question:
•• How are large molecules transported into How are large molecules transported into and out of the plasma membranes?and out of the plasma membranes?
Answer:Answer:
•• Exocytosis and EndocytosisExocytosis and Endocytosis
ExocytosisExocytosis
•• Cell Cell secretes macromoleculessecretes macromolecules (proteins and (proteins and other biochemicals) other biochemicals) outout of cell.of cell.
•• Part of the Endomembrane System:Part of the Endomembrane System: the fusion of transport vesicles with plasma membrane.
EndocytosisEndocytosis
• The energyenergy requiring movementmovement of particlesparticles(foreign or natural)(foreign or natural) intointo the cell.
•• 3 types of endocytosis:3 types of endocytosis:A.A. PhagocytosisPhagocytosisB.B. PinocytosisPinocytosisC.C. ReceptorReceptor--mediated endocytosismediated endocytosis
A. A. PhagocytosisPhagocytosis
•• Cell eating:Cell eating: cells engulf particles with pseudopodiapseudopodia and pinches off a food pinches off a food vacuolevacuole..
•• Two examples:Two examples:1.1. White Blood CellWhite Blood Cell2.2. AmoebaAmoeba
FoodFoodVacuoleVacuole White Blood Cell
Bacteria
B. PinocytosisB. Pinocytosis• Cell drinking: droplets of extracellular fluid
are absorbedabsorbed intointo the cell by small vesiclessmall vesicles.
•• Example:Example:1.1. FungiFungi
Food Particles
Hyphae
C. ReceptorC. Receptor--Mediated EndocytosisMediated Endocytosis
• Importing specific macromolecules (hormones)specific macromolecules (hormones)intointo the cell by the inward budding of vesiclesinward budding of vesiclesformed from coated pits (receptors).
Hormones
Receptors
Liver Cell