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The Plasma Membrane - Gateway to the Cell
7/30/2019 The Plasma Membrane - Gateway to the Cell G. Podgorski, Biol. 1010
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Homeostasis Balanced internal condition of cells
The Plasma Membrane 7/30/2019 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010
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Functions of Plasma Membrane
The Plasma Membrane 7/30/2019 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton G. Podgorski, Biol. 1010
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Functions of Plasma Membrane
The Plasma Membrane 7/30/2019 Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces bind cells together (junctions) Contains the cytoplasm (fluid in cell) G. Podgorski, Biol. 1010
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Structure of the Cell Membrane
The Plasma Membrane 7/30/2019 Structure of the Cell Membrane G. Podgorski, Biol. 1010
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Cell or Plasma Membrane
Composed of double layer of phospholipids and proteins Surrounds outside of ALL cells Controls what enters or leaves the cell Living layer Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Cholesterol Outside of cell Phospholipids 6 6
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The Plasma Membrane 7/30/2019 FLUID MOSAIC MODEL FLUID- because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. G. Podgorski, Biol. 1010
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Mosaic
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Cell Membrane Polar heads are hydrophilic “water loving”
The Plasma Membrane Cell Membrane 7/30/2019 Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses G. Podgorski, Biol. 1010
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Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT
The Plasma Membrane Cell Membrane 7/30/2019 The cell membrane is made of 2 layers of phospholipids called the lipid bilayer Hydrophobic molecules pass easily; hydrophilic DO NOT G. Podgorski, Biol. 1010
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Semipermeable Membrane
The Plasma Membrane Semipermeable Membrane 7/30/2019 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O G. Podgorski, Biol. 1010
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video
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Types of Transport Across Cell Membranes
The Plasma Membrane 7/30/2019 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010
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Simple Diffusion Requires NO energy
The Plasma Membrane 7/30/2019 Simple Diffusion Requires NO energy Molecules move from area of HIGH to LOW concentration G. Podgorski, Biol. 1010
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The Plasma Membrane 7/30/2019 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY G. Podgorski, Biol. 1010
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Diffusion of Liquids The Plasma Membrane 7/30/2019
G. Podgorski, Biol. 1010
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Diffusion through a Membrane
The Plasma Membrane 7/30/2019 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) G. Podgorski, Biol. 1010
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Diffusion across a membrane Semipermeable membrane
The Plasma Membrane 7/30/2019 Osmosis Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Semipermeable membrane G. Podgorski, Biol. 1010
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Diffusion of H2O Across A Membrane
The Plasma Membrane 7/30/2019 Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010
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http://highered. mcgraw-hill
video
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Cell in Isotonic Solution
The Plasma Membrane 7/30/2019 Cell in Isotonic Solution 10% NaCl 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCl 90% H2O What is the direction of water movement? equilibrium The cell is at _______________. G. Podgorski, Biol. 1010
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Cell in Hypotonic Solution
The Plasma Membrane 7/30/2019 Cell in Hypotonic Solution 10% NaCl 90% H2O CELL 20% NaCl 80% H2O What is the direction of water movement? G. Podgorski, Biol. 1010
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Cell in Hypertonic Solution
The Plasma Membrane 7/30/2019 Cell in Hypertonic Solution 15% NaCl 85% H2O ENVIRONMENT CELL 5% NaCl 95% H2O What is the direction of water movement? G. Podgorski, Biol. 1010
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Cells in Solutions The Plasma Membrane 7/30/2019
G. Podgorski, Biol. 1010
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NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane 7/30/2019 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS G. Podgorski, Biol. 1010
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Osmosis in Red Blood Cells
The Plasma Membrane 7/30/2019 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010
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isotonic hypotonic hypertonic hypertonic isotonic hypotonic
The Plasma Membrane 7/30/2019 isotonic hypotonic hypertonic hypertonic isotonic hypotonic G. Podgorski, Biol. 1010
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Three Forms of Transport Across the Membrane
The Plasma Membrane Three Forms of Transport Across the Membrane 7/30/2019 G. Podgorski, Biol. 1010
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Passive Transport Simple Diffusion Doesn’t require energy
The Plasma Membrane 7/30/2019 Passive Transport Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. G. Podgorski, Biol. 1010
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Facilitated diffusion
The Plasma Membrane 7/30/2019 Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. G. Podgorski, Biol. 1010
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Active Transport Requires energy or ATP
The Plasma Membrane 7/30/2019 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient G. Podgorski, Biol. 1010
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The Plasma Membrane 7/30/2019 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump G. Podgorski, Biol. 1010
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