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Cellular Transport Yeast cells stained with fluorescent dye The cell membrane The Cell Membrane • Selectively permeable (semi-permeable) allows only certain substances to pass through cannot control the movement of water Cell membrane The fluid mosaic model • double layer of lipids with proteins scattered throughout • flexible, phospholipids move with in the membrane Parts of the cell membrane • Phospholipids – lipids with a phosphate group attached to one end – makes molecule polar so it can react with water Parts of the Cell Membrane • Transport Proteins- allows needed substances or waste materials through membrane Parts of the Cell Membrane • Cholesterol – stabilizes the phospholipids – does not allow fatty acid chains to stick together cholesterol Type of Cell Transport • • • • • Simple diffusion Osmosis Facilitated diffusion Active transport Endocytosis/Exocytosis Diffusion • Particles move from an area of high concentration to an area of low concentration • Moves “down” or “with” the concentration gradient • Does not require energy Diffusion • Factors effecting the rate of diffusion 1. temperature (as temp increases rate increases) 2. pressure (as pressure increases rate increases) 3. steepness of the concentration gradient (the steeper the gradient the faster the diffusion) Osmosis • Movement of WATER across a cell membrane • Cell has no control • continues to move until [inside] = [outside] called dynamic equilibrium • [ ]- means “the concentration of” Types of Solutions • Isotonic • Hypotonic • Hypertonic Types of Solutions • Isotonic – [water inside] = [water outside] • Hypotonic – [water inside] < [water outside] – solutes are higher inside the cell – water flows in, cell swells – cell could burst if continues • Hypertonic – [water inside] > [water outside] – solutes are higher outside the cell – water leaves cell, cell shrinks Types of Solutions Isotonic Hypotonic Water particle Solute particle Hypertonic Types of Solutions • Water always moves toward the solution with the highest concentration of solute Type of Solutions Notice water level rises on side of membrane with the highest solute concentration Types of Solutions Effects on Animal Cells The pictures below are red blood cells in different concentrations of salt solution. Identify which pictures are hypotonic, isotonic, and hypertonic solutions. Isotonic Hypertonic Hypotonic Types of Solutions Effects on Plant Cells Which of these cells are in a hypotonic solution? Hypertonic solution? Hypotonic Hypertonic Facilitated Diffusion • moves down the concentration gradient with aid of protein • Does not use energy • most glucose moved this way Passive Transport • NO energy required • Diffusion, Osmosis, and Facilitated Diffusion are all forms of passive transport Active Transport • Requires energy • moves from an area of low concentration to an area of high concentration • moves “up” or “against” the concentration gradient • glucose moved from blood stream into liver for storage Active Transport Moving large particles across the cell membrane • Endocytosis – movement of large particles into the cell • Exocytosis – movement of large particles out of the cell Endocytosis Exocytosis