2 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 membraneWhy do we need to regulate osmosis?To maintain homeostasis because the plasma membrane is naturally permeable to water
4 OsmosisHow long does water diffuse in a solution? Until it has reached equilibrium (even distribution)What controls osmosis?The concentration gradientWhat is a concentration gradient?The unequal distribution of particles
5 Types of Solutions: Isotonic Remember: Salt Sucks!!! "ISO" means the sameDefinition: 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
6 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 swellsWhat happens: The cell swells upAnimal Cell- swell until they burstPlant 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)
8 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 shrivelsWhat happens: Cell shrivels upAnimal cell- shrivels upPlant cell – loses pressure as the plasma membrane shrinks away from the cell wall; the plant wilts = plasmolysis
13 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 requiredWhat do materials need to cross the plasma membrane? Transport proteinsWhat is this process called?Facilitated diffusion
14 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.
15 Active Transport: Requires Energy Active Transport – Movement of particles through a membrane against a concentration gradient…low concentration high concentration…Energy is requiredHow 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.
16 Type ofTransportProtein Used?Direction ofMovementRequiresenergy fromthe cell?Classificationof transportSimpleDiffusionNoWithConcentrationGradientPassiveFacilitatedYes- channel protein or carrier proteinActiveYes- carrier proteinAgainstYes
18 Transport of Large Particles Endocytosis- The process by which a cell surrounds and takes in material from its environmentExplain the process of endocytosis- the material is engulfed and enclosed by a portion of the cells plasma membrane.
19 ExocytosisExocytosis- the expels or secretes materials from a cell.
20 Transport of Large Particles Phagocytosis- the engulfing and ingesting of solid particles- “cell eating”Pinocytosis- the ingestion of fluid into a cell- “cell drinking”