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Outcomes: • Identify the factors which influence the rate and direction of diffusion. • Identify how osmosis is related to diffusion and the value of osmosis to living organisms. • Examine the mechanisms of active transport by identifying and explaining the two processes. • Compare the similarities and differences between active and passive transport. **Don’t have to write these out** Passive and Active Transport Unit 2- Cell Structure and Function Cellular Transport Cellular transport moves substances within the cell and moves substances into and out of the cell There are 2 types: 1. 2. Passive Transport Active Transport Passive Transport These types of transport do not require energy a) b) c) Diffusion Facilitated Diffusion Osmosis A) Diffusion Remember from years before that particles in solids, liquids, and gasses are in constant random motion (Particle Theory of Matter) Substances dissolved in water move constantly in random motion The random motion of these particles creates DIFFUSION The amount of a substance in a certain area is called CONCENTRATION Substances diffuse from an area of higher concentration to an area of lower concentration Watch the following video and draw the diagram on the next page: http://www.youtube.com/watch?v=Um6O oN81rb4 Diagram of Diffusion Diffusion occurs until there is an equal concentration of particles in an area/cell The particles continue to move randomly, but there is no overall change- this is called DYNAMIC EQUILIBRIUM Rate of Diffusion 3 main factors affect the rate that diffusion occurs 1. Concentration 2. Temperature 3. When concentration is high, diffusion happens quickly because there are more particles to collide with each other When temperature increases, the particles collide more quickly Pressure When pressure increases, the particles collide more quickly B) Facilitated Diffusion While water can diffuse readily across a plasma membrane, most other substances need help Happens through carrier and channel proteins The CHANNEL PROTEINS in the plasma membrane of the cell are used to diffuse ions and small molecules across the cell membrane (draw the diagram below) http://kentsimmons.uwinnipeg.ca/cm1504/Image132.gif CARRIER PROTEINS are also used to move substances across a cell membrane by changing shape to help diffusion in a cell (Draw the diagram) http://www.biologyco rner.com/resources/si mpdiff.jpg C) Osmosis The diffusion of water across a selectively permeable membrane is OSMOSIS Regulating the movement of water across the plasma membrane is an important factor in maintaining homeostasis (draw the next diagram) http://www.biologycorner.com/resources/osmosis.jpg If the concentration of solute is higher on one side of the cell membrane, the water will move towards the higher solute concentration This diffusion happens until dynamic equilibrium occurs Isotonic Solution When a cell is in a solution that has the same concentration of water and solutes is said to be in an ISOTONIC solution Water moves into and out of the cell at the same rate and cells keep their normal shape Hypotonic Solution If a cell is in a solution that has a lower concentration of solute, the cell is said to be in a HYPOTONIC solution There is more water outside of the cell than inside the cell which causes water to move into the cell The water moving into the cell creates osmotic pressure In an animal cell, the water may enter the cell so much so that it bursts A plant cell will not burst if there is a high osmotic pressure because the cell wall is very rigid Hypertonic Solution When the concentration of the solute outside of the cell is higher than inside Water moves outside the cell Animal cells may shrivel because of water loss Plant cells wilt because the water vacuole is empty Draw the diagram: http://4.bp.blogspot.com/yiAZAMJRq4s/Ta79K3vVk8I/AAAAAAAAACE/MhfD0z_ABi8/s1600/ hypo.jpg Video Explanation http://www.youtube.com/watch?v=AYN wynwaALo Active Transport This happens when substances have to move from an area of lower concentration to an area of higher concentration This process makes sure that cells have the proper amount of substances inside of them These forms of cellular transport REQUIRE the use of ENERGY by the cell a) b) Pumps (carrier proteins) Endocytosis/Exocytosis A) Pumps (Carrier Proteins) Carrier proteins can move substances against a concentration gradient Some pumps move one type of substance in one direction across the plasma membrane Other pumps move two substances in both directions across the plasma membrane Sodium Potassium Pump This is a common type of pump moves 3 sodium ions out of the cell moves 2 potassium ions into the cell ATP (a form of energy) breaks down into ADP to do this Video demonstration http://www.youtube.com/watch?v=Q73uJ 8WlY_E http://4.bp.blogspot.com/_207DNIaLgc/TOaSu8u3q7I/AAAAAAAAAV4/9QLnFO82wQA/s1600/07_16Sodium PotassiumPump.jpg B) Endocytosis & Exocytosis Particles that are too large to travel through the plasma membrane leave or enter the cell differently Endocytosis ENDOCYTOSIS is when a cell surrounds something outside of the cell The cell membrane pinches off and leaves the substance inside the cell The substance is now in a vesicle to travel throughout the cell Exocytosis Is when substances leave the cell by vesicles joining the plasma membrane to expel the substance http://www.kscience.co.uk/as/module1/pictures/endoexo.jpg
