NOTES Transport Through The Cell Membrane What is cell transport? Cell Transport when substances move into or out of cells Cell Transport when substances move into or out of cells In order to get into or out of the cell, substances must pass through the cell membrane In order to get into or out of the cell, substances must pass through the cell membrane Substances in a living thing naturally move from areas of high concentration (where there is a lot of that substance) to areas of low concentration (where there is less of that substance) Substances in a living thing naturally move from areas of high concentration (where there is a lot of that substance) to areas of low concentration (where there is less of that substance) What are the 2 types of cell transport? 1.Passive Transport When substances move in or out of cells from areas of high concentration to areas of low concentration Passive Transport - Diffusion Diffusion - the process by which molecules spread from areas of high concentration, to areas of low concentration(H L) Dynamic Equilibrium - When molecules are evenly spread throughout a space Passive Transport - Osmosis Osmosis is the process by which WATER moves from areas of high concentration to areas of low concentration (H L) Relationship between diffusion of solute molecules and osmosis Diffusion and osmosis happen in opposite directions Diffusion is the movement of solute Osmosis is the movement of solvent (water) Solutions that have relatively high concentrations of solute, have relatively low concentrations of solvent, and vice versa Passive Transport EX. If there is a lot of sodium outside of a cell, the sodium moves into the cell by diffusion and water moves out of the cell by osmosis EX. If there is a lot of sodium outside of a cell, the sodium moves into the cell by diffusion and water moves out of the cell by osmosis Two Solutions Are Separated By A Selectively Permeable Membrane Solution A has a high concentration of solute compared to solution B Solution B has a high concentration of water compared to Solution A So what happens? Two Solutions Are Separated By A Selectively Permeable Membrane Solute moves through the membrane from Solution A to Solution B (Diffusion) Solution A becomes less concentrated, Solution B becomes more concentrated Two Solutions Are Separated By A Selectively Permeable Membrane Water moves through the membrane from Solution B to Solution A (Osmosis) Solution B becomes more concentrated, Solution A becomes less concentrated Two Solutions Are Separated By A Selectively Permeable Membrane Dynamic equilibrium is reached Solute and Water move back and forth equally Rate of Diffusion The rate (speed) of diffusion is influenced by 3 factors: A. Temperature: As Temp. increases, the rate of diffusion also increases T D B. Concentration: As the Conc. increases, the rate of diffusion also increases C D C. Pressure: As the Pressure increases, the rate of diffusion DECREASESPD Passive Transport - Facilitated Diffusion Facilitated Diffusion - the movement of molecules from H L, through protein molecules in the cell membrane The Rime of the Ancient Mariner By Samuel Taylor Coleridge (written in ) Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink. Salt-Cured Meat Meat or fish preserved or cured with salt The only widely available method of preserving food until the 19 th century Salt prevents the growth of bacteria by drawing water out of bacteria cells by osmosis Salted meat was a staple of the mariner's diet in the Age of Sail. It was stored in barrels, and often had to last for months spent out of sight of land. What are the 2 types of cell transport? 2. 2.Active Transport When the cell uses energy to move substances in or out from an area of low concentration to an area of high concentration (L H) Active Transport The cell must USE ENERGY because substances do not naturally move from low concentration to high concentration The cell must USE ENERGY because substances do not naturally move from low concentration to high concentration The cell must also use energy to move very large particles into or out of the cell The cell must also use energy to move very large particles into or out of the cell Bulk Transport Bulk Transport - the movement of large amounts of material into or out of the cell Endocytosis movement into the cell Exocytosis movement out of the Both processes occur when the material is too large to pass through the cell membrane Two Types of Endocytosis A. Phagocytosis = cell eating cell takes in large solid molecules Ex: white blood cell engulfing a bacteria B. Pinocytosis = cell drinking cell takes in large amount of fluid Video Clip of Active Transport Another way to look at it What are the effects of passive transport on cells? As the cells external environment changes, passive transport causes water and other substances to continuously move into and out of cells Turgor Pressure pressure in a cell caused by water Plant cells need the correct amount of turgor pressure to stay rigid Elodea Cells Before and After Placement in a Hypertonic Solution 1. 1.What happens if there is a lower concentration of substances outside the cell? Type of Solution Hypotonic Turgor Pressure High Cell Shape Swollen Plant Cell - Hypotonic Cell is turgid (rigid from high turgor pressure) 2. 2.What happens if the concentration of substances outside of the cell is equal to the cytoplasm Type of Solution Isotonic Turgor Pressure Normal Cell Shape Normal (Flaccid if plant) Plant Cell - Isotonic Cell is flaccid (turgor pressure not quite high enough to maintain rigidity) 3. 3.What happens if there is a higher concentration of substances outside of the cell? Type of Solution Hypertonic Turgor Pressure Low Cell Shape Shriveled Plant Cell - Hypertonic Cell is plasmolyzed (turgor pressure too low to hold membrane against cell wall) Animal Cells in Different Solutions Cytolysis animal cell bursts in hypotonic solution Crenation when a cell shrinks in a hypertonic solution Osmotic Effects on Cells How do I figure out the direction of passive transport? Look at the solution outside of the cell. Compared to the cytoplasm, is the concentration of substances higher, lower, or equal? Diffusion Which way will the substances move? (into cell, out of cell, in or out equally) Osmosis Which way will water move? (into cell, out of cell, in or out equally) To sum up If there is a lot of substance outside a cell, substance moves in (diffusion), water moves out (osmosis) and the cell shrivels If there is a lot of substance outside a cell, substance moves in (diffusion), water moves out (osmosis) and the cell shrivels If there is a lot of substance inside a cell, substance moves out (diffusion), water moves in (osmosis) and the cell swells If there is a lot of substance inside a cell, substance moves out (diffusion), water moves in (osmosis) and the cell swells These processes happen naturally (passive transport), if the cell wants the opposite to happen, it must use energy (active transport) These processes happen naturally (passive transport), if the cell wants the opposite to happen, it must use energy (active transport) Cells need a steady supply of energy for active transport otherwise they would not be able to adjust to their environment Cell Transport Animationsology1111/animations/transport1.swfology1111/animations/transport1.swf