Plasma Membrane

Plasma Membrane - The Plasma Membrane - Gateway to the Cell...

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Unformatted text preview: The Plasma Membrane - Gateway to the Cell copyright cmassengale 1 Photograph of a Cell Photograph Membrane Membrane copyright cmassengale 2 Cell Membrane The cell membrane is flexible and flexible allows a unicellular organism to move copyright cmassengale 3 Homeostasis • Balanced internal condition of cells • Also called equilibrium • Maintained by plasma membrane controlling what enters & leaves the cell copyright cmassengale 4 Functions of Plasma Functions Membrane Membrane Protective barrier Protective Regulate transport in & out of cell (selectively permeable) (selectively Allow cell recognition Allow Provide anchoring sites for filaments of cytoskeleton of copyright cmassengale 5 Functions of Plasma Functions Membrane Membrane Provide a binding site for enzymes Provide Interlocking surfaces bind cells together (junctions) together Contains the cytoplasm (fluid in cell) Contains copyright cmassengale 6 Structure of the Cell Structure Membrane Membrane copyright cmassengale 7 Membrane Components Phospholipids Cholesterol Proteins (peripheral and integral) copyright cmassengale 8 Carbohydrates (glucose) copyright cmassengale 9 Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar & contains a –PO4 group & glycerol copyright cmassengale 10 FLUID MOSAIC MODEL FLUID- because individual phospholipids and because proteins can move side-to-side within the layer, like it’s a liquid. like MOSAIC- because of the pattern produced by the because scattered protein molecules when the membrane copyright cmassengale 11 is viewed from above. is Cell Membrane Polar heads are hydrophilic “water loving” hydrophilic Nonpolar tails are hydrophobic “water fearing” hydrophobic Makes membrane “Selective” in what crosses12 copyright cmassengale copyright cmassengale 13 Cell Membrane The cell membrane is Hydrophobic made of 2 layers of molecules pass phospholipids called the phospholipid easily; hydrophilic lipid bilayer bilayer copyright cmassengale 14 DO NOT Solubility • Materials that are soluble in lipids can pass through the cell membrane easily copyright cmassengale 15 Semipermeable Membrane Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O copyright cmassengale 16 Semipermeable Membrane Semipermeable Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. copyright cmassengale 17 Types of Transport Types Across Cell Membranes Membranes copyright cmassengale 18 Simple Diffusion • Requires NO NO energy • Molecules move from area of HIGH to LOW to concentration copyright cmassengale 19 DIFFUSION Diffusion is a PASSIVE process PASSIVE which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY copyright cmassengale 20 Diffusion of Liquids copyright cmassengale 21 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to copyright cmassengale 22 LOW) Osmosis • Diffusion of water across a membrane membrane • Moves from HIGH water potential water (low solute) to (low LOW water potential (high potential solute) solute) Diffusion across a membrane copyright cmassengale Semipermeabl e membrane 23 Diffusion of H2O Across A Across Membrane Membrane High H2O potential Low H2O potential copyright cmassengale 24 Low solute concentration High solute concentration Aquaporins • Water Channels • Protein pores used during OSMOSIS WATER MOLECULES copyright cmassengale 25 Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O NO NET NO MOVEMENT MOVEMENT What is the direction of water movement? equilibrium The cell is at _______________. copyright cmassengale 26 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? copyright cmassengale 27 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? copyright cmassengale 28 Cells in Solutions copyright cmassengale 29 Isotonic Solution Hypotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypertonic Solution CYTOLYSIS PLASMOLYSIS copyright cmassengale 30 Cytolysis & Plasmolysis Cytolysis copyright cmassengale Plasmolysi 31 Osmosis in Red Blood Cells Isotonic Hypotonic copyright cmassengale Hypertonic 32 What Happens to Blood Cells? copyright cmassengale 33 hypotonic hypertonic isotonic hypertonic isotonic hypotonic copyright cmassengale 34 Three Forms of Transport Across the Membrane copyright cmassengale 35 Passive Transport Simple Diffusion Doesn’t require energy Doesn’t Moves high to low high concentration concentration Example: Oxygen or Oxygen water diffusing into a cell water and carbon dioxide carbon diffusing out. diffusing copyright cmassengale 36 Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or Examples: Glucose amino acids moving from amino blood into a cell. blood copyright cmassengale 37 Proteins Are Critical to Proteins Membrane Function Membrane copyright cmassengale 38 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 copyright cmassengale 39 Facilitated Diffusion Molecules will randomly move through the pores in Channel pores Proteins. Proteins copyright cmassengale 40 Facilitated Diffusion • Some Carrier proteins do not proteins extend through the membrane. the • They bond and They drag molecules drag through the lipid bilayer and release them on the opposite side. the copyright cmassengale 41 Carrier Proteins • Other carrier Other proteins change shape change to move materials across the cell membrane membrane copyright cmassengale 42 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient copyright cmassengale 43 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump copyright cmassengale 44 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped copyright cmassengale 45 out; creates a membrane potential Moving the “Big Stuff” Exocytosi s­ moving things out. Molecules are moved out of the cell by vesicles that fuse Molecules moved vesicles fuse with the plasma membrane. with This is how many hormones are secreted and how nerve This hormones copyright cmassengale 46 cells communicate with one another. cells Exocytosis Exocytic Exocytic vesicle immediately after fusion with plasma membrane. membrane. copyright cmassengale 47 Moving the “Big Stuff” Large molecules move materials into the cell by Large one of three forms of endocytosis. three copyright cmassengale 48 Pinocytosis Most common form of endocytosis. Most common Takes in dissolved molecules as a vesicle. Takes dissolved copyright cmassengale 49 Pinocytosis • Cell forms an Cell invagination invagination • Materials Materials dissolve in water dissolve to be brought into cell into • Called “Cell Called Drinking” Drinking” copyright cmassengale 50 Example of Pinocytosis mature transport vesicle pinocytic vesicles forming copyright cmassengale Transport across a capillary cell (blue). 51 Receptor-Mediated Endocytosis Some integral proteins have receptors on Some integral receptors their surface to recognize & take in hormones, cholesterol, etc. hormones, copyright cmassengale 52 Receptor-Mediated Endocytosis copyright cmassengale 53 copyright cmassengale 54 Endocytosis – Phagocytosis Endocytosis Used to engulf large particles such as engulf food, bacteria, etc. into vesicles bacteria Called “Cell Eating” copyright cmassengale Called “Cell 55 copyright cmassengale 56 Phagocytosis About to Occur copyright cmassengale 57 Phagocytosi s - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) copyright cmassengale 58 Exocytosis The opposite of endocytosis is exocytosis. Large The molecules that are manufactured in the cell are molecules released through the cell membrane. released Inside Cell copyright cmassengale Cell environment 59 copyright cmassengale 60 ...
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This note was uploaded on 11/09/2011 for the course BIO 110 taught by Professor Harmon during the Winter '11 term at BYU.

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