microsoft power point 05_a closer look membranes[1]
TRANSCRIPT
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A Closer Look at MembranesA Closer Look at Membranes
Chapter 5Chapter 5
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Cystic FibrosisCystic Fibrosis
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Cystic FibrosisCystic Fibrosis
Caused by defective protein channelCaused by defective protein channel(CFTR) in epithelial cells(CFTR) in epithelial cells
-- membranesmembranes
Thick mucus clogs airways and ductsThick mucus clogs airways and ducts
throughout bodythroughout body Usually fatal by age 30Usually fatal by age 30
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Main component ofMain component ofcell membranescell membranes
Lipid BilayerLipid Bilayer
lipid
fluid propertiesfluid properties
Fatty acid tailsFatty acid tails
sandwichedsandwichedbetween hydrophilicbetween hydrophilicheadsheads
Figure 5.2cPage 82
bilayer
fluid fluid
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Fluid Mosaic ModelFluid Mosaic Model
Membrane is a mosaic ofMembrane is a mosaic of PhospholipidsPhospholipids
SterolsSterols
ProteinsProteins
Most phospholipids and some proteins canMost phospholipids and some proteins candrift through membranedrift through membrane
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Membrane ProteinsMembrane Proteins
receptorprotein
adhesionprotein recognition
protein
active transporters
communicationprotein passivetransporter
Figure 5.5Page 85
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Question 1Question 1
1. What is a lipid bilayer?1. What is a lipid bilayer?
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Answer 1Answer 1
1. What is a lipid bilayer?1. What is a lipid bilayer?
. .. .phospholipids oriented so that thephospholipids oriented so that thetails intermingle.tails intermingle.
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Question 2Question 2
2. Name three types of proteins found in2. Name three types of proteins found inplasma membranes.plasma membranes.
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Answer 2Answer 2
2. Name three types of proteins found in2. Name three types of proteins found inplasma membranes.plasma membranes.
transport, receptor, recognition,transport, receptor, recognition,adhesive, and communicativeadhesive, and communicative
proteinsproteins
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Membrane ExperimentsMembrane Experiments
Split membranes reveal embeddedSplit membranes reveal embeddedproteinsproteins
In-text figure
Page 86
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Hybrid humanHybrid human--mouse cell shows somemouse cell shows someproteins drift within membraneproteins drift within membrane
Membrane ExperimentsMembrane Experiments
human cell mouse cell hybrid cell
Figure 5.6Pa e 86
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Question 3Question 3
3. What do hybrid human mouse3. What do hybrid human mousemembranes show?membranes show?
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Answer 3Answer 3
3. What do hybrid human mouse cells3. What do hybrid human mouse cellsshow?show?
Hybrid humanHybrid human--mouse cell showsmouse cell showssome proteins drift withinsome proteins drift within
membrane.membrane.
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Selective PermeabilitySelective Permeability
O2, CO2,and other small, nonpolarmolecules; some water
molecules
glucose and other large, polar,water-soluable molecules; ions,water molecules
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Membrane Crossing MechanismsMembrane Crossing Mechanisms
Diffusion across lipid bilayerDiffusion across lipid bilayer
Passive transportPassive transport
Active transportActive transport
EndocytosisEndocytosis
ExocytosisExocytosis
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Concentration GradientConcentration Gradient
Means the number of molecules or ions inMeans the number of molecules or ions inone region is different than the number inone region is different than the number inanother regionanother region
In the absence of other forces, aIn the absence of other forces, asubstance moves from a region where it issubstance moves from a region where it is
more concentrated to one where its lessmore concentrated to one where its lessconcentratedconcentrated -- down gradientdown gradient
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DiffusionDiffusion
The net movement of like molecules orThe net movement of like molecules orions down a concentration gradientions down a concentration gradient
Although molecules collide randomly, theAlthough molecules collide randomly, thenet movement is away from the place withnet movement is away from the place with
the most collisions (down gradient)the most collisions (down gradient)
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Factors AffectingFactors AffectingDiffusion RateDiffusion Rate
Steepness of concentration gradientSteepness of concentration gradient Steeper gradient, faster diffusionSteeper gradient, faster diffusion
Smaller molecules, faster diffusionSmaller molecules, faster diffusion
TemperatureTemperature
Higher temperature, faster diffusionHigher temperature, faster diffusion
Electrical or pressure gradientsElectrical or pressure gradients
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Example of DiffusionExample of Diffusion
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Question 4Question 4
4. What is meant by the term, selectively4. What is meant by the term, selectivelypermeable?permeable?
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Answer 4Answer 4
4. What is meant by the term, selectively4. What is meant by the term, selectivelypermeable?permeable?
molecules to cross it, but blocks others.molecules to cross it, but blocks others.
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Question 5Question 5
5. What molecules can easily pass across5. What molecules can easily pass acrossthe plasma membrane (with nothe plasma membrane (with noassistance ?assistance ?
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Answer 5.Answer 5.
5. What molecules can easily pass across5. What molecules can easily pass acrossthe plasma membrane (with nothe plasma membrane (with noassistance ?assistance ?
Small nonpolar molecules and someSmall nonpolar molecules and some
water. (ex. Oxygen, carbon dioxidewater. (ex. Oxygen, carbon dioxide
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Span the lipid bilayerSpan the lipid bilayer Interior is able to open to both sidesInterior is able to open to both sides
Transport ProteinsTransport Proteins
solutesolute
Move waterMove water--soluble substances acrosssoluble substances across
a membranea membrane
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Passive and Active TransportPassive and Active Transport
Doesnt requireDoesnt requireenergy inputsenergy inputs
Passive Transport Active Transport Requires ATPRequires ATP
Solutes diffuseSolutes diffuse
through a channelthrough a channelinside the proteinsinside the proteins
interiorinterior Net movement isNet movement is
down concentrationdown concentration
gradientgradient
pumppump Pumps solute againstPumps solute against
its concentrationits concentration
gradientgradient
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glucose transporter
solute (glucose) high
low
Passive Transport
Figure 5.10Figure 5.10Page 88Page 88
Stepped Art
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ATP
higher calciumconcentration
lower calcium concentration
Active Transport
ADP
Pi
Figure 5.11Figure 5.11Page 89Page 89
Stepped Art
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OsmosisOsmosis
Water molecules tend to diffuse downWater molecules tend to diffuse down
water concentration gradientwater concentration gradient
Total number of molecules or ionsTotal number of molecules or ions
dictates concentration of waterdictates concentration of water
TonicityTonicity -- relative solute concentrationsrelative solute concentrations
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TonicityTonicity2% sucrosesolution
distilled water
10%sucrosesolution
2%sucrose
solution
HypotonicConditions
HypertonicConditions
IsotonicConditions
Figure 5.13
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Fluid PressureFluid Pressure
Hydrostatic pressureHydrostatic pressure Turgor pressureTurgor pressure
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PressuresPressures
''TurgorTurgor pressurepressure' or turgidity is the' or turgidity is themainmain pressurepressure of the cell contentsof the cell contentsa ainst the cell wall in lant cells anda ainst the cell wall in lant cells and
bacteria cells, determined by the waterbacteria cells, determined by the watercontent of the vacuole, resulting fromcontent of the vacuole, resulting fromosmoticosmotic pressurepressure, i.e. the, i.e. the hydrostatichydrostatic
pressurepressure produced by a solution in aproduced by a solution in aspace divided by aspace divided by a semipermeablesemipermeablemembrane.membrane.http://en.wikipedia.org/wiki/Turgor_pressurehttp://en.wikipedia.org/wiki/Turgor_pressure
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Endocytosis andEndocytosis andExocytosisExocytosis
plasma membrane
cytoplasm
Exocytosis
cytoplasm
Endocytosis
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Endocytosis PathwaysEndocytosis Pathways
Bulk phaseBulk phase ReceptorReceptor--mediatedmediated
clathrin Figures 5.17, 5.18
Pages 92, 93
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MembraneMembraneCyclingCycling
Exocytosis andExocytosis andendocytosisendocytosis
clathrin
con nua y rep acecon nua y rep aceand withdrawand withdrawpatches of plasmapatches of plasma
membranemembrane
lysosome
Golgibody
Figure 5.19
Page 93