Post on 03-Apr-2018
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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?
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