Warm-Up #4 11/1/12 1) What are the 2 other names for the cell membrane? 2) If a molecule is too big to go through the membrane alone, what must it use? 3) Label A-D on the Picture below. 4) What is the quiz tomorrow on? Passive Transport: Diffusion and Osmosis Unit 4 Chapter 5 What are we doing? • Essential Question: • How do organisms maintain homeostasis? • Objectives: • Explain how an equilibrium is established as a result of diffusion. • Distinguish between diffusion and osmosis. Passive Transport • Movement of substances across the cell membrane without the use of ATP (Energy) Concentration Gradient • The difference in the concentration of molecules across a space. • Diffusion always occurs DOWN the concentration gradient. Equilibrium • Equi--equal • When the concentration of molecules of a substance is the SAME throughout a space Diffusion • Simplest type of passive transport • NO energy needed • Always goes from an area of higher concentration to lower concentration • Example: • Gas exchange in lungs • Photosynthesis Rate of Diffusion • Rate depends on three things: • 1. Temperature • Higher the temperature faster the diffusion • 2. Size • Smaller the molecule, faster the diffusion • 3. Type of Molecules • Bigger molecules will not pass through without energy input Osmosis • Diffusion of water across a semipermeable membrane • Move from high to low concentration When does this happen? • Water moves from areas of LOW solute concentration to areas of HIGH solute concentrations • Will do this until they are evenly distributed Hypertonic Solution • The concentration of solute molecules outside the cell is higher than the concentration of solutes inside the cell. • Water Diffuses OUT of the Cell until equilibrium occurs Animal vs. Plants in Hypertonic Solutions • Animal Cell: • Cell shrivels and shrinks • Plant Cell: • Cell membrane pulls away from the cell wall Plasmolysis • Plants lose water through osmosis. • It occurs when the cell membrane peels away from the cell wall. • The plant shrivels and dies. Hypotonic • The concentration of solute molecules outside the cell is lower than the concentration of solutes inside the cell • Water diffuses INTO the cell until equilibrium is reached Animal vs. Plant Cells--Hypotonic • Animal Cell • Cell will swells and bursts • Plant Cell • DOES NOT burst because of cell wall • Called Turgor Pressure Isotonic Solution • The concentration of solutes outside and inside the cell are equal. • Water diffuses into and out of the cell at equal rate Help…I Need Somebody… • Facilitated Diffusion • Use of carrier proteins to help substances move in or out of the cell • No Energy Needed What do the Proteins Do? • Carry molecules across the membrane—carrier proteins • Change shape to help the molecule pass through Solution Isotonic: The concentration of solutes is the same inside and outside of the cell Hypertonic: Solution has a higher solute concentration than the cell Hypotonic: Solution has a lower solute concentration than the cell Animal Cell Plant Cell WARM-UP #4 11/3/11 1) What does passive transport not require? 2) What are 2 types of passive transport? 3) The movement of molecules across a membrane is called……? 4) Osmosis is the movement of____.