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The Plasma Membrane - Gateway to the Cell
4/19/2017 The Plasma Membrane - Gateway to the Cell G. Podgorski, Biol. 1010
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Photograph of a Cell Membrane… it’s really thin
The Plasma Membrane 4/19/2017 Photograph of a Cell Membrane… it’s really thin ~8nm G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move G. Podgorski, Biol. 1010
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Homeostasis Balanced internal condition of cells
The Plasma Membrane 4/19/2017 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 4/19/2017 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of the cytoskeleton G. Podgorski, Biol. 1010
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Functions of Plasma Membrane
The Plasma Membrane 4/19/2017 Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces help 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 4/19/2017 Structure of the Cell Membrane G. Podgorski, Biol. 1010
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Membrane Components Phospholipids Proteins (peripheral and integral)
The Plasma Membrane 4/19/2017 Phospholipids Proteins (peripheral and integral) Cholesterol Carbohydrates (glucose) G. Podgorski, Biol. 1010
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Phospholipids Make up the cell membrane
The Plasma Membrane 4/19/2017 Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar & contains a –PO4 group & glycerol G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 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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Cell Membrane Polar heads are hydrophilic “water loving”
The Plasma Membrane Cell Membrane 4/19/2017 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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The Plasma Membrane 4/19/2017 G. Podgorski, Biol. 1010
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Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT
The Plasma Membrane Cell Membrane 4/19/2017 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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The Plasma Membrane 4/19/2017 Solubility Materials that are soluble in lipids can pass through the cell membrane easily G. Podgorski, Biol. 1010
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Semipermeable Membrane
The Plasma Membrane Semipermeable Membrane 4/19/2017 Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O G. Podgorski, Biol. 1010
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Semipermeable Membrane
The Plasma Membrane Semipermeable Membrane 4/19/2017 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. G. Podgorski, Biol. 1010
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Types of Transport Across Cell Membranes
The Plasma Membrane 4/19/2017 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010
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Simple Diffusion Requires NO energy
The Plasma Membrane 4/19/2017 Simple Diffusion Requires NO energy Molecules move from areas of HIGH to LOW concentration G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 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 4/19/2017
G. Podgorski, Biol. 1010
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Diffusion through a Membrane
The Plasma Membrane 4/19/2017 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (from HIGH to LOW) G. Podgorski, Biol. 1010
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Diffusion across a membrane Semipermeable membrane
The Plasma Membrane 4/19/2017 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 4/19/2017 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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Aquaporins Water Channels Protein pores used during OSMOSIS
The Plasma Membrane 4/19/2017 Aquaporins Water Channels Protein pores used during OSMOSIS WATER MOLECULES G. Podgorski, Biol. 1010
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Cell in Isotonic Solution
The Plasma Membrane 4/19/2017 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 4/19/2017 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 4/19/2017 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 4/19/2017
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NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane 4/19/2017 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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Cytolysis & Plasmolysis
The Plasma Membrane 4/19/2017 Cytolysis & Plasmolysis Cytolysis Plasmolysis G. Podgorski, Biol. 1010
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Osmosis in Red Blood Cells
The Plasma Membrane 4/19/2017 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010
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What Happens to Blood Cells?
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isotonic hypotonic hypertonic hypertonic isotonic hypotonic
The Plasma Membrane 4/19/2017 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 4/19/2017 G. Podgorski, Biol. 1010
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Passive Transport Simple Diffusion Doesn’t require energy
The Plasma Membrane 4/19/2017 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 4/19/2017 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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How are Proteins Critical to Membrane Function?
The Plasma Membrane 4/19/2017 How are Proteins Critical to Membrane Function? G. Podgorski, Biol. 1010
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Types of Transport Proteins
The Plasma Membrane 4/19/2017 Types of Transport Proteins Channel proteins are embedded in the cell membrane & have a pore for materials to cross Carrier proteins can change shape to move material from one side of the membrane to the other G. Podgorski, Biol. 1010
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Facilitated Diffusion
The Plasma Membrane 4/19/2017 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. G. Podgorski, Biol. 1010
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Facilitated Diffusion
The Plasma Membrane 4/19/2017 Facilitated Diffusion Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 Carrier Proteins Other carrier proteins change shape to move materials across the cell membrane G. Podgorski, Biol. 1010
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Active Transport Requires energy or ATP
The Plasma Membrane 4/19/2017 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 4/19/2017 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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Sodium-Potassium Pump
The Plasma Membrane 4/19/2017 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential G. Podgorski, Biol. 1010
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Exocytosis- moving things out.
The Plasma Membrane Moving the “Big Stuff” 4/19/2017 Exocytosis- moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve cells communicate with one another. G. Podgorski, Biol. 1010
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The Plasma Membrane Exocytosis 4/19/2017 Exocytic vesicle immediately after fusion with plasma membrane. G. Podgorski, Biol. 1010
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The Plasma Membrane Moving the “Big Stuff” 4/19/2017 Large molecules move materials into the cell by one of three forms of endocytosis. G. Podgorski, Biol. 1010
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Pinocytosis Most common form of endocytosis.
The Plasma Membrane Pinocytosis 4/19/2017 Most common form of endocytosis. Takes in dissolved molecules as a vesicle. G. Podgorski, Biol. 1010
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Pinocytosis Cell forms an invagination
The Plasma Membrane 4/19/2017 Pinocytosis Cell forms an invagination Materials dissolve in water to be brought into cell Called “Cell Drinking” G. Podgorski, Biol. 1010
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Example of Pinocytosis
The Plasma Membrane Example of Pinocytosis 4/19/2017 mature transport vesicle pinocytic vesicles forming Transport across a capillary cell (blue). G. Podgorski, Biol. 1010
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Receptor-Mediated Endocytosis
The Plasma Membrane 4/19/2017 Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. G. Podgorski, Biol. 1010
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Receptor-Mediated Endocytosis
The Plasma Membrane Receptor-Mediated Endocytosis 4/19/2017 G. Podgorski, Biol. 1010
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Endocytosis – Phagocytosis
The Plasma Membrane 4/19/2017 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” G. Podgorski, Biol. 1010
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Phagocytosis About to Occur
The Plasma Membrane Phagocytosis About to Occur 4/19/2017 G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment G. Podgorski, Biol. 1010
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The Plasma Membrane 4/19/2017 Any Questions? G. Podgorski, Biol. 1010
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