Cellular Transport On the following slides, the blue sections highlight the main points; summarize the slides for your notes. Underlined words = vocabulary!

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Plasma Membrane AKA Cell Membrane Video

Fluid Mosaic Model  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: –Proteins are used in transport –Cholesterol stabilizes the phospholipids –Carbohydrate chains are markers, think “ID” tags

What is a concentration gradient?  Cells have to move things through membranes on a regular basis (food, water, waste, etc.).  The concentration gradient measures the amount of solutes in the fluid within and out of a cell SimulationSimulation

What is diffusion?  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 or carrier proteins imbedded in the plasma membrane as “doorways”. s/Cells_Membranes/diffusion.gif

What is osmosis?  Water is one of the most important nutrient that cells need in order to function.  Osmosis is the diffusion of water through a selectively permeable (to permeate is to pass through) membrane and 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. AnimationAnimation mages/Cells_Membranes/osmosis.gif

Passive vs Active Transport  Diffusion and osmosis are processes within the cell that occur naturally, without the need for energy; considered passive transport.  Active transport is when cells uses energy to move molecules against the concentration gradient. –Carrier proteins act as “doorways” to move molecules and substances in and out of the cell from a low concentration to a high concentration. VideoVideo active_transport.jpg

r%208/8-14.jpg Label:  High vs low concentration for each of the three scenarios  Diffusion  Facilitated diffusion  Active transport

Knowledge Check  Take a deep breath!  How does oxygen get into your blood stream? How does it “diffuse”?  Turn and talk to your neighbor on the above question. –When you breathe in, where is oxygen MOST concentrated? –Where is oxygen LEAST concentrated? –Where will the O 2 diffuse? Why? 8.jpg

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 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 travel out and it will shrink. mages/tonicity1.jpeg Solutions and Cells

Sketch the graphics (be sure to include the H 2 O arrows!!!) I”S”otonic = “S”ame! Hype”R”tonic – The cell sh”R”inks! Hyp”O”tonic – The cell gr”O”ws!

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 as a result of the above? "Osmosis, cellular process of." Experiment Central. U*X*L, Science In Context. Web. 26 Sept

What is endocytosis?  Endocytosis = cell surrounds and takes in material –Phagocytosis: the process when cells move and shift the cytoplasm to surround a substance; means “cell eating” –Pinocytosis: “cell drinking” the process when cells move liquid inside their membranes –Video 1 Video2Video 1Video2 –AnimationAnimation

What is exocytosis?  Exocytosis = cell expels materials  Video 1 Video 1 d%3A98646f6a2e e2ec defc4766dc84 7a5e49e0fa5e48%2BIMAGE_THUMB_POSTCARD%2BI MAGE_THUMB_POSTCARD.1

Limitations to Cell Size  In order for cells to diffuse materials easily in and out of their membranes, they must 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 – DNA in the nucleus within eukaryotic cells carries instructions to make proteins; these proteins are needed throughout the cell (in almost all organelles) and for important functions.  The a large cell, proteins could not be made quickly enough to meet the demands. 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).  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