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 1 Photograph of a Cell Photograph Membrane Membrane 2 Cell Membrane The cell membrane is flexible and flexible allows a unicellular organism to move 3 Homeostasis • Balanced internal condition of cells • Also called equilibrium • Maintained by plasma membrane controlling what enters & leaves the cell 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 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 6 Structure of the Cell Structure Membrane Membrane 7 Membrane Components Phospholipids Cholesterol Proteins (peripheral and integral) 8 Carbohydrates (glucose) Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar & contains a –PO4 group 9 FLUID MOSAIC MODEL Fluid mosaic model FLUID- because individual phospholipids and because proteins can move around freely within the layer, like it’s a liquid. like MOSAIC- because of the pattern produced by the because scattered protein molecules when the membrane 10 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 crosses11 12 Cell Membrane The cell membrane is Hydrophobic made of 2 layers of molecules pass phospholipids called the phospholipid easily; hydrophillic lipid bilayer bilayer 13 DO NOT Solubility • Materials that are soluble in lipids can pass through the cell membrane easily 14 Semipermeable Membrane Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O 15 Semipermeable Membrane Semipermeable Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. 16 Types of Transport Types Across Cell Membranes Membranes 17 Simple Diffusion • Requires NO NO energy • Molecules move from area of HIGH to LOW to concentration 18 DIFFUSION Diffusion is a PASSIVE process PASSIVE which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY 19 Diffusion of Liquids 20 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to 21 LOW) Osmosis • Diffusion of water across a membrane membrane • Moves from HIGH Moves water potential water (low solute) to LOW water potential (high potential solute) solute) Diffusion across a membrane Semipermeabl e membrane 22 Diffusion of H2O Across A Across Membrane Membrane High H2O potential Low solute concentration Low H2O potential 23 High solute concentration 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 _______________. 24 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? 25 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? 26 Cells in Solutions 27 Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution Hypertonic Solution CYTOLYSIS PLASMOLYSIS 28 Cytolysis & Plasmolysis Cytolysis Plasmolysi 29 Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic 30 hypotonic hypertonic isotonic hypertonic isotonic hypotonic 31 Three Forms of Transport Across the Membrane 32 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 33 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 34 Proteins Are Critical to Proteins Membrane Function Membrane 35 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 36 Facilitated Diffusion Molecules will randomly move through the pores in Channel pores Proteins. Proteins 37 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 38 Carrier Proteins • Other carrier Other proteins change shape change to move materials across the cell membrane membrane 39 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient 40 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump 41 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped 42 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 43 cells communicate with one another. cells Exocytosis Exocytic Exocytic vesicle immediately after fusion with plasma membrane. membrane. 44 Moving the “Big Stuff” Large molecules move materials into the cell by Large one of three forms of endocytosis. three 45 Pinocytosis Most common form of endocytosis. Most common Takes in dissolved molecules as a vesicle. Takes dissolved 46 Pinocytosis • Cell forms an Cell invagination invagination • Materials Materials dissolve in water dissolve to be brought into cell into • Called “Cell Called Drinking” Drinking” 47 Example of Pinocytosis p ino c y tic ve s ic le s fo rm ing m a ture tra ns p o rt ve s ic le Transport across a capillary cell (blue). 48 Receptor-Mediated Endocytosis Some integral proteins have receptors on Some integral receptors their surface to recognize & take in hormones, cholesterol, etc. hormones, 49 Receptor-Mediated Endocytosis 50 Endocytosis – Phagocytosis Endocytosis Used to engulf large particles such as engulf food, bacteria, etc. into vesicles bacteria Called “Cell Eating” Called “Cell 51 Phagocytosis About to Occur 52 Phagocytosi s - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) 53 The opposite of endocytosis is exocytosis. Large The molecules that are manufactured in the cell are molecules released through the cell membrane. released Exocytosis Inside Cell Cell environment 54 ...
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