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Cellular Transport. Movement of Materials In and Out of a Cell. Plasma Membrane. Maintains homeostasis (stable environment) Membrane is “ selectively permeable ” Only certain things can pass in and out. Structure of the Plasma Membrane. Fluid Mosaic Model Membrane is not rigid
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Cellular Transport Movement of Materials In and Out of a Cell
Plasma Membrane • Maintains homeostasis (stable environment) • Membrane is “selectively permeable” • Only certain things can pass in and out
Structure of the Plasma Membrane Fluid Mosaic Model Membrane is not rigid Molecules can move back and forth (fluid)
Phospholipid Bi-layer • 2 layers of Phospholipids • Hydrophobic tails and hydrophilic heads
Cholesterol molecules: sometimes found embedded in membrane to give it more strength and rigidity. Carbohydrate Chains: help cells identify each other
Membrane Proteins • Protein Channels • Provide pathway for movement of certain materials • Anchor Proteins • Anchor molecules in membrane so they don’t move around • Enzyme Proteins • Take part in chemical reactions
Receptor Proteins • Act as binding sites for specific molecules • Cellular communication • Recognize foreign cells • Tell cell to begin or stop activity
Movement in a Liquid Medium • Cytoplasm has many different things dissolved in it. • Solvent = water • Solute = stuff dissolved (ex: sugar, salt) • Solution = the mixture of solvent and solute • Concentration = how much is dissolved
All molecules are in constant random motion, so over time they will move from one location to another.
Passive TransportDoesn’t require energy • Diffusion: • Movement of materials through the cell membrane. • Higher concentration to lower concentration • Does not require energy (ATP) • Ex:oxygen, carbon dioxide, water
Dynamic Equilibrium: a point of balance that is reached when concentrations stop changing (but particles still moving!)
Example of Diffusion Higher Concentration Outside Particles Diffuse Into Cell Equilibrium Reached (Diffuse In & Out Equally)
Facilitated Diffusion: • Protein channels facilitate (help) movement of charged ions and large molecules like glucose to cross cell membrane • Energy (ATP) not needed
Osmosis: • Movement (diffusion) of WATER through the cell membrane • From high concentration to low (of water) • No energy needed
Aquaporins: • Water channel proteins • Involved in osmosis • Allow water to move easily through membrane by diffusion • Type of facilitated diffusion Oil (fat) and water don’t mix Channel helps water get through fatty membrane!!!
Water moves into an area that is more concentrated with solute particles!!!! • Equilibrium is reached and concentrations are equal on both sides of membrane
Osmosis Water moves to area where water is less concentrated
Osmotic Pressure: force caused by net movement of water into or out of cell
Isotonic Solution: of the same “strength” • Same concentration as cell • Hypertonic Solution: “above strength” • More concentrated than cell • Hypotonic Solution: “below strength” • Less concentrated than cell
What will Happen? • To a cell in a: • Isotonic Solution? • Hypertonic Solution? • Hypotonic Solution? • Which way will water move? • Will it fill up and burst, shrink, or stay the same? • Types of Solutions: http://youtu.be/7-QJ-UUX0iY • Egg Experiment: http://youtu.be/SSS3EtKAzYc
Plasmolysis: when a plant cell loses water • Normal plant cell – large vacuole stores water • In salt water, or in times of drought – water leaves cell to go into surroundings (wilts)
Active Transport: • Requires energy (ATP) • Materials are moved from low to high concentration
Protein Pumps: • Membrane proteins • Move small molecules and ions across membrane • Against concentration gradient (low to high) • Requires energy (ATP)
Endocytosis • Folding in the membrane to form a vacuole • Take in large molecules, clumps of food or whole cells • Requires energy
Types of Endocytosis • Phagocytosis • Cell “eating” • Cell engulf large particles by sending out extensions of cytoplasm • Ex: • Amoeba sends out pseudopods, • White blood cells eat bacteria and damaged cells
Pinocytosis • Cell “drinking” • Cell takes in liquid • “Pinching in” of cell membrane to create a storage vacuole
Exocytosis • Cells releasing (excreting) materials • Membrane of vacuole fuses with cell membrane
Inner Life of the Cell • http://youtu.be/yKW4F0Nu-UY