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CH 8: Cellular Transport Diffusion and Osmosis What is diffusion? - the movement of molecules from regions of high concentration to regions of low concentration, “down” a concentration gradient. What is osmosis? – The diffusion of water across a selectively permeable membrane Why do we need to regulate osmosis? – To maintain homeostasis because the plasma membrane is naturally permeable to water Osmosis How long does water diffuse in a solution? - Until it has reached equilibrium (even distribution) What controls osmosis? – The concentration gradient What is a concentration gradient? – The unequal distribution of particles Types of Solutions: Isotonic Remember: Salt Sucks!!! "ISO" means the same Definition: When the concentration of water is the same inside and outside the cell so a cell remains the same. Both animal and plant cells retain normal shape and pressure Types of Solutions: Hypotonic • The prefix "HYPO" means less -Less water inside the cell than outside so water will move into the cell. • Definition: When the concentration of water is lower inside the cell than outside the cell so the cell swells • What happens: The cell swells up • Animal Cell- swell until they burst • Plant Cell- swell beyond their normal size as pressure increases; this pressure is called turgor pressure. The plasma membrane presses against the cell wall and makes the cell more firm (why grocers mist fruits at the market) Types of Solution: Hypotonic Types of Solution: Hypertonic • The prefix "HYPER" means more -More water inside the cell than outside so the water leaves the cell. • Definition: When the concentration of water is higher inside the cell than outside the cell so the cell shrivels • What happens: Cell shrivels up • Animal cell- shrivels up • Plant cell – loses pressure as the plasma membrane shrinks away from the cell wall; the plant wilts = plasmolysis Types of Solution http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm Red Blood Cells in Solution Burst---------------Swollen----------Normal-----------------Plasmolysis--------- • http://www.wiley.com/college/boyer/0470003790/animations/m embrane_transport/membrane_transport.htm • http://www.northland.cc.mn.us/biology/Biology1111/animations/t ransport1.html Passive Transport: No Energy Required • Passive Transport -the movement of particles across a membrane that goes with the concentration gradient…high concentration low concentration…and energy is not required • What do materials need to cross the plasma membrane? Transport proteins • What is this process called? Facilitated diffusion Types of Transport Proteins • Channel Proteins- form channels that allow specific molecules to flow through. • Carrier Proteins - change shape to allow a substance to pass through the plasma membrane. Active Transport: Requires Energy • Active Transport – Movement of particles through a membrane against a concentration gradient…low concentration high concentration…Energy is required • How does active transport occur? A carrier protein binds with the substance to be transported. The protein changes shape so that the particle can be released into the cell--like the opening of a door. Type of Transport Transport Protein Used? Direction of Movement Requires energy from the cell? Classification of transport Simple Diffusion No With Concentration Gradient No Passive Facilitated Diffusion Yes- channel protein or carrier protein With Concentration Gradient No Passive Active Transport Yes- carrier protein Against Concentration Gradient Yes Active Passive Transport vs. Active Transport Transport of Large Particles • Endocytosis- The process by which a cell surrounds and takes in material from its environment • Explain the process of endocytosisthe material is engulfed and enclosed by a portion of the cells plasma membrane. Transport of Large Particles • Phagocytosis- the engulfing and ingesting of solid particles- “cell eating” • Pinocytosis- the ingestion of fluid into a cell- “cell drinking” http://www.researchandteaching.bio.uci. edu/lectureprojects.html Exocytosis • Exocytosis- the expels or secretes materials from a cell.