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Chapter 5 http://www.ems.psu.edu/~bannon/moledyn.html http://www.visionlearning.com/library/module_vi ewer.php?mid=57&l=&c3= http://www.phy.davidson.edu/brownian.html http://www.wisconline.

WHY or WHY NOT? A Membrane with pores big enough to allow dye to pass NO, because that would require an input of energy, or some sort of organizing force, right?

1 Chapter ewer.php?mid=57&l=&c3= From your experience on this planet, do you think that the dye molecules would ever, spontaneously move from evenly spread out, back to a concentrated drop? WHY or WHY NOT? A Membrane with pores big enough to allow dye to pass NO, because that would require an input of energy, or some sort of organizing force, right? On our planet, systems do not become more organized/orderly spontaneously. Would you agree that things like dye molecules tend to spontaneously become less organized, if prompted to do so? Remember that molecules are in constant, random motion! 1

2 Looking at the situation on the left, versus the situation on the right, what can you say, if anything about the ENERGY of the two situations? HIGH POTENTIAL ENERGY LOW POTENTIAL ENERGY Energy Diffusion Potential Energy Kinetic Energy Energy is defined as the capacity to perform work. Work is done whenever an object is moved against an opposing force (or moved where it would not spontaneously move) The spontaneous movement of molecules of any kind, from an area where they are more concentrated to where they are less concentrated Conservation of Energy Energy can never be destroyed or created, it can only be converted from one form to another. (like from potential to kinetic) All energy conversions, though, are inefficient, and produce some heat. Heat is a type of not very useful kinetic energy. It is the energy contained in the random motion of atoms and molecules. Heat is not useful energy because it can t easily be harnessed to do any work. HIGH POTENTIAL ENERGY Low POTENTIAL ENERGY Notice that as the dye molecules moved from high potential energy to low potential energy, they bumped into other molecules. These bumps believe it or not, increase the random motion (rotation and vibration) (heat) of the molecules in the solution around it. 2

spontaneously move from a less stable (higher energy) state to a more stable (lower energy) state, if prompted to do

more stable states fuel Once started, the process will proceed, without a further input of energy. A free ride!

cross the cell membrane from an area of high concentration to an area of low concentration.

3 What is happening to the energy? HIGH POTENTIAL ENERGY Energy conversion LOW POTENTIAL ENERGY Systems (or snowboarders on top of a hill) will spontaneously move from a less stable (higher energy) state to a more stable (lower energy) state, if prompted to do so. Systems move to more stable states Unstable systems are rich in free (available) energy and tend to move toward more stable states fuel Once started, the process will proceed, without a further input of energy. A free ride! Waste or simpler molecules Examples in the Cell Examples in the Cell Small, uncharged molecules will spontaneously cross the cell membrane from an area of high concentration to an area of low concentration. DIFFUSION of O 2, CO 2 FREE RIDE oxygen Facilitated Diffusion Na+ or H 2 O Energetically, still a free ride Ions and water are repelled by the membrane. To diffuse down their concentration gradient, they need a passageway across the membrane. 3

Examples in the Cell Diffusion of Water oxygen Na+ or H 2 O Energetically, still a free ride Facilitated Diffusion: diffusion of a molecule down its

Facilitated Diffusion Diffusion of Water The direction of osmosis (water movement across a membrane) is determined by solute concentration, or

A selectively permeable membrane is used to separate two solutions. The membrane is selectively permeable only to H 2 O.

4 Examples in the Cell Diffusion of Water oxygen Na+ or H 2 O Energetically, still a free ride Facilitated Diffusion: diffusion of a molecule down its concentration gradient via a membrane protein channel/pore Osmosis- The passive transport of water molecules across a selectively permeable membrane. Facilitated Diffusion Diffusion of Water The direction of osmosis (water movement across a membrane) is determined by solute concentration, or tonicity of a solution Water will always move toward the saltier/more sugary/more solute-packed solution! A selectively permeable membrane is used to separate two solutions. The membrane is selectively permeable only to H 2 O. (water is free to move, but the sugar molecules may not pass through!!) What happens? Which way does the water move? At Time ZERO Water diffused to the right. Water diffused toward the hypertonic solution (the solution with more sugar) 4

Tonicity When comparing two solutions, the solution with the higher concentration of a solute (say, sugar) is said to be hypertonic to the other. How could you refer to these solutions?

5 Tonicity When comparing two solutions, the solution with the higher concentration of a solute (say, sugar) is said to be hypertonic to the other. How could you refer to these solutions? 1 scoop 4 scoops 2 scoops Isotonic Hypertonic Hypotonic A B Solution A is to Solution B. Solution B is to Solution C. Solution C is to Solution A. C How could you refer to these solutions? Osmosis in Cells without Cell Walls 1 scoop 4 scoops 2 scoops 2 scoops Isotonic Hypotonic Hypertonic A B C D Solution C is to Solution D. Net movement of H 2 O in Isotonic, Hypotonic and Hypertonic Solutions Osmosis in Cells with Cell Walls Isotonic Hypotonic Hypertonic Osmosis helps a plant cell maintain turgor pressure in a hypotonic environment Loss of turgor pressure results in plants becoming flaccid Plasmolysis: cell membrane pulling away from the cell wall 5

Net movement of H 2 O in Hypotonic Isotonic, and Hypertonic Solutions Hypotonic Isotonic Hypertonic Active Transport Active transport is used to move ions or molecules against

6 Net movement of H 2 O in Hypotonic Isotonic, and Hypertonic Solutions Hypotonic Isotonic Hypertonic Active Transport Active transport is used to move ions or molecules against a concentration gradient (from a low concentration to a high concentration) Movement against a concentration gradient requires energy. The energy is supplied by ATP ENERGY! ATP 6

Cellular Transport and the Cell Cycle

Chapter 8 Cellular Transport and the Cell Cycle In your textbook, read about osmosis: diffusion of water. Reinforcement and Study Guide Section 8.1 Cellular Transport Complete the table by checking the