Unit #4 Cellular Transport The blue sections summarize key information and vocabulary terms are underlined.

Plasma Membrane Textbook Reference pg Video

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Fluid Mosaic Model Textbook Reference pg. 178  Plasma membranes are commonly described as a fluid mosaic model; it is made of various molecules in a complicated phospholipid bilayer.  The plasma membrane is fluid, embedded with trans-membrane proteins, cholesterol, carbohydrate chains. –Proteins are used in transport –Cholesterol stabilizes the phospholipids –Carbohydrate chains are markers, think “ID” tags

Solutes versus Solvents Textbook Reference pg. 149  Cells have to move things through membranes on a regular basis (food, water, waste, etc.).  The concentration measures the amount of solute in a solvent (stuff in it, EX sugar in tea).SimulationSimulation

What is diffusion? Textbook Reference pg ,  In a solution, the particles are moving constantly (in a glass of water, molecules are still moving).  Diffusion is the movement of particles from a high concentration to a lower concentration to reach equilibrium (relatively the same or equal on all sides).  Facilitated diffusion is the process by which cells uses channel proteins or carrier proteins imbedded in the plasma membrane as “doorways”. s/Cells_Membranes/diffusion.gif

Diffusion Mini-Lab  Remember the lab demo using cornstarch and iodine.  Look at the two molecules, what is the difference? The corn starch molecule is 24 atoms large, while the iodine is only 2 atoms.  Which atom was able to “pass through” the bag membrane?  Discuss with your neighbor. Chemical = Iodine (I 2 ) Chemical = Corn Starch Glucose Polymer (C 6 H 12 O 6 ) Iodine! Cornstarch was too large, but we can tell the iodine diffused because of the change in color!

Knowledge Check  Take a deep breath!  How does oxygen get into your blood stream?  List your thoughts on the above question. Your answer must include:: –Where is oxygen MOST concentrated? –Where is oxygen LEAST concentrated? –Where will the O 2 diffuse? Why? tificial-blood-8.jpg

What is osmosis? Textbook Reference pg  Water is one of the most important items that cells need in order to function.  Osmosis is the diffusion of water through a selectively permeable (to permeate is to pass through) membrane.  The rate of osmosis is controlled by the concentration of solutes in a cell’s environment.  Water will move easily, until the concentration is relatively equal on both sides of the cell membrane. mages/Cells_Membranes/osmosis.gif

 Hypotonic solution has a higher solute concentration inside the cell, so water will travel in to the cell (grow).  An isotonic solution (or “same strength”) is one where the concentration inside the cell matches the outside of the cell – there is equitable movement in and out.  Hypertonic solution has a higher solute concentration outside the cell, so water will move out of the cell and it will shrink. mages/tonicity1.jpeg Solutions and Cells Textbook Reference pg

 Sketch the graphics (be sure to include the arrows!!!)  Click on the simulations to view diffusion and osmosis.  Simulation #1 Simulation LSzYgyU/s1600/Bio+hypotonic,+Isotonic,+Hypertonic.gif Hyp”O”tonic Solutions – The cell gr”O”ws! Hype”R”tonic Solutions – The cell sh”R”inks! I”S”otonic = “S”ame!

Knowledge Check  Examine the diagram to the right.  Turn to your neighbor and answer the following questions: : –Where is water MOST concentrated in the top cell? –Where is water MOST concentrated in the bottom cell? –How will the cells change in the next as a result of the above? "Osmosis, cellular process of." Experiment Central. U*X*L, Science In Context. Web. 26 Sept

Passive Transport vs Active Transport Textbook Reference pg  Diffusion and osmosis are processes within the cell that occur naturally, without the need for energy; they are forms of passive transport.  Active transport is a process by which cells uses energy to move molecules against the concentration gradient. –Carrier proteins within the plasma membrane act as “doorways” to move molecules and substances in and out of the cell against the gradient (from a low concentration to a high concentration). Video Video active_transport.jpg

What is phagocytosis? Textbook Reference pg. 200  Phagocytosis: the process when cells move shift the cytoplasm to surround a substance; means “cell eating” –Endocytosis = cell surrounds and takes in material –Exocytosis = cell expels wastes  Video Video

Limitations to Cell Size Textbook Reference pg  In order for cells to diffuse materials easily in and out of their membranes, their size has to remain relatively small. 1.Diffusion - if cells are too large, it would take entirely too long for the materials to diffuse and reach their destinations.

Size Limitations Cont. 2.Proteins - The nucleus within eukaryotic cells carries genetic information embedded with the DNA molecule to make proteins; these proteins are needed throughout the cell (in almost all organelles) and for important functions.  The cell must stay small because proteins could not be made quickly enough to meet the demands for a large cell. AAAAAAAAhM/XiFyUjna6NQ/s1600/nucleic+acid.jpg

Size Limitations Cont. 3.Surface Area - As cells increase in size, the volume within them increases as well (the surface area to volume ratio).  The surface area is the sum of all the areas of all the shapes that cover the surface of the object.  As the volume increases, the need for materials is much greater than the surface area available to diffuse oxygen, nutrients, and expel wastes.  Cells must, therefore, remain small. hill.com/sites/dl/free/ /383917/bz.gif