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Cell Transport Cell Membrane- Homeostasis They are Selectively Permeable= some things can get in and others can not! Role: “Gate Keeper” Membranes control what molecules can enter and leave the cell! Membranes are impermeable to: Molecules that can not get in or out: • Ions • Polar molecules water • Large molecules glucose amino acids Membranes are permeable to: Molecules that can get in and out of the cell: • Hydrophobic molecules: steroids CO2 O2 N2 • Small & uncharged urea & ethanol Polar molecules and IonsHomeostasis Transport proteins: allow polar molecules & ions to move through the membrane!! • Ions Na+, Cl-, K+ • Polar molecules sugar , water Passive transport The cell does not use energy to move molecules across the membrane. • Molecules naturally flow from areas of high concentration to areas of low concentration. Concentration Gradient Imaginary slope that shows the direction of the flow of molecules. start stop Equilibrium Molecules will continue to move from high to low until they are equal on both sides of the membrane. Start Stop Three types of Passive Transport 1. Diffusion: movement of hydrophobic fluids and gasses: Dyes, oxygen 2. Osmosis: movement of water 3. Facilitated Diffusion: requires transport proteins: glucose Facilitate = help Osmosis Water is essential to maintaining homeostasis in the cell and the body!! • It is polar- impermeable • Requires a channel protein- facilitated Aquaporin 2003 Nobel Prize -Biochemistry Osmosis and Solutions The intracellular and extracellular environments of the cell determine which way water will flow. Cellular environment determines the direction of water flow! Intra= inside or within Extra= outside Solution A solution is the sum of the solute and solvent. Solute: something that can dissolve: sugar, salt Solvent: the dissolver: water How are the solutions in the beaker similar and different? Direction water flows The solute concentration on both sides of the cell membrane determines the direction that water flows!! Beaker solution = environment Environment is relative to the cell- add cell 3 Types of Solutions Based upon the solute ratio outside : inside the cell. Hypertonic solution- more solute less water than the cell Hypotonic solution- less solute more water than the cell Isotonic solution- equal solutes on both sides of the cell membrane Hyper= more Hypo= less Iso= equal Hypertonic Solution Has more solutes than the cell = less water water moves out of the cell. Salt Water Hypotonic Solution Has less solute than the cell = more water water moves into the cell Draw it! Salt = S Water = W Isotonic Solution Equal solutes inside and outside the cellno net flow in or out of the cell. Dynamic equilibriummolecules will move in or out of the cell but – no net gain or loss of water. Cells React to Their Environment Animal cells- lack a cell wall and will lyse in a hypotonic solution. Plants cells- cell will not burst in a hypotonic solution – Cell Wall Lys= break apart Organisms, Adaptations, Osmosis • Unicellular aquatic animal-like organisms. • Lack a cell wall. Contractile vacuolepumps out excess water to maintain homeostasis Sharks and Osmoregulation What would happen to a shark if it was placed in a freshwater aquarium? Exception: Bull Sharks- have been found in the Mississippi as far north as Illinois. Group discussion- Questions