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Transcript of The Plasma Membrane and Homeostasis 2 Functions of Plasma Membrane Protective barrier Regulate...
The Plasma Membrane The Plasma Membrane and Homeostasisand Homeostasis
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Functions of Plasma Functions of Plasma MembraneMembrane Protective barrierProtective barrier
Regulate transport in & out of Regulate transport in & out of cell cell (selectively permeable)(selectively permeable)
Allow cell recognitionAllow cell recognition
Provide anchoring sites for Provide anchoring sites for filaments filaments of cytoskeletonof cytoskeleton
Provide a binding site for Provide a binding site for enzymesenzymes
Interlocking surfaces bind cells Interlocking surfaces bind cells together (junctions)together (junctions)
Homeostasis – Maintaining a Homeostasis – Maintaining a BalanceBalance
Cells must keep the proper Cells must keep the proper concentration of nutrients and concentration of nutrients and water and eliminate wastes.water and eliminate wastes.
The plasma membrane is The plasma membrane is selectively permeable – it will selectively permeable – it will allow some things to pass allow some things to pass through, while blocking other through, while blocking other things.things.
Structure of the Plasma Structure of the Plasma MembraneMembrane
Lipid bilayer – two sheets of lipids Lipid bilayer – two sheets of lipids (phospholipids).(phospholipids).– Found around the cell, the nucleus, Found around the cell, the nucleus,
vacuoles, mitochondria, and vacuoles, mitochondria, and chloroplasts.chloroplasts.
– Embedded with proteins and Embedded with proteins and strengthened with cholesterol strengthened with cholesterol molecules.molecules.
What’s a Phospholipid?What’s a Phospholipid?
It’s a pair of fatty acid chains and a It’s a pair of fatty acid chains and a phosphate group attached to a phosphate group attached to a glycerol backbone.glycerol backbone.– Polar (water-soluble) heads face Polar (water-soluble) heads face
out and the nonpolar fatty acids out and the nonpolar fatty acids hang inside.hang inside.
Membrane ProteinsMembrane Proteins
1. Determine what particles can 1. Determine what particles can pass through the membrane.pass through the membrane.
2. Serve as enzymes (may speed 2. Serve as enzymes (may speed reactions).reactions).
3. Act as markers that are 3. Act as markers that are recognized by chemicals and recognized by chemicals and molecules from the inside and the molecules from the inside and the outside of the cell (the immune outside of the cell (the immune system).system).
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Simple DiffusionSimple Diffusion Molecules move Molecules move
from area of from area of HIGH HIGH to LOWto LOW concentrationconcentration
Requires Requires NONO energy to make the energy to make the molecules move.molecules move.• passive processpassive process
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Diffusion of LiquidsDiffusion of Liquids
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Diffusion through a MembraneDiffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
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OsmosisOsmosis Diffusion of waterDiffusion of water
across a across a membranemembrane
Moves fromMoves from HIGH HIGH water molecule water molecule concentrationconcentration (low solute) to(low solute) to LOW water LOW water molecule molecule concentrationconcentration (high solute)(high solute)
Diffusion across a membrane
Semipermeable
membrane
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Diffusion of HDiffusion of H22O Across A O Across A
MembraneMembrane
High H2O concentrationLow solute concentration
Low H2O concentrationHigh solute concentration
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Cell in Isotonic SolutionCell in Isotonic Solution
CELLCELL
10% NaCL90% H2O
10% NaCL
90% H2O
What is the direction of water movement?The cell is at _______________.equilibrium
ENVIRONMENTENVIRONMENT
NO NET NO NET MOVEMENMOVEMENTT
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Cell in Hypotonic SolutionCell in Hypotonic Solution
CELLCELL
10% NaCL90% H2O
40% NaCL
60% H2O
What is the direction of water movement?
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Cell in Hypertonic SolutionCell in Hypertonic Solution
CELLCELL
15% NaCL85% H2O
5% NaCL95% H2O
What is the direction of water movement?
ENVIRONMENTENVIRONMENT
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Cells in SolutionsCells in Solutions
copyright cmassengale
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Which cell is at homeostasis?Which cell is at homeostasis?
Cytolysis Plasmolysis
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Osmosis in Red Blood CellsOsmosis in Red Blood Cells
IsotonicIsotonic Hypotonic
Hypertoniccopyright cmassengale
What Happens to Blood Cells?What Happens to Blood Cells?
copyright cmassengale 20
Cellular TransportCellular Transport
DiffusionDiffusion – movement of particles from – movement of particles from an area of high concentration to an area an area of high concentration to an area of low concentration.of low concentration.– Caused by Brownian motion Caused by Brownian motion
(movement of particles because of (movement of particles because of the movement of their atoms).the movement of their atoms).
– Continues until an equilibrium is Continues until an equilibrium is reached (no gradient).reached (no gradient).
– Dynamic equilibrium – particles move Dynamic equilibrium – particles move freely and are evenly distributed.freely and are evenly distributed.
Cellular Transport [1]Cellular Transport [1]
Passive transportPassive transport – no energy is – no energy is needed to move particles.needed to move particles.
– Facilitated diffusionFacilitated diffusion – embedded – embedded proteins act as tunnels allowing proteins act as tunnels allowing particles to “fall” through.particles to “fall” through.
Cellular Transport [2]Cellular Transport [2]
Active transport – energy is needed Active transport – energy is needed to move particles.to move particles.
– Carrier proteins – embedded proteins Carrier proteins – embedded proteins change shape to open and close change shape to open and close passages across the membrane.passages across the membrane.
– Endocytosis – taking something into Endocytosis – taking something into the cell.the cell.
– Exocytosis – expelling something from Exocytosis – expelling something from the cell.the cell.
OsmosisOsmosis
Diffusion of water across a Diffusion of water across a selectively permeable membrane.selectively permeable membrane.
Occurs until water is balanced on Occurs until water is balanced on both sides of the membrane.both sides of the membrane.
Cell ConcentrationsCell Concentrations
Hypertonic solutions – more Hypertonic solutions – more dissolved solute.dissolved solute.
Hypotonic solutions – less dissolved Hypotonic solutions – less dissolved solute.solute.
Isotonic solutions – the same Isotonic solutions – the same dissolved solute.dissolved solute.
Overcoming OsmosisOvercoming Osmosis
Contractile vacuoles – expel excess Contractile vacuoles – expel excess water from bacterial cells that live water from bacterial cells that live in water.in water.
Turgor pressure – water pressure Turgor pressure – water pressure in a plant cell. Loss of turgor in a plant cell. Loss of turgor pressure causes wilting pressure causes wilting (plasmolysis).(plasmolysis).