Movement of Substances

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Movement of Substances

  1. 1. Movement of Substances
  2. 2. Diffusion equal conc. of ink Eg 1 http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html Eg 2 high conc. of ink low conc. of ink
  3. 3. Diffusion <ul><li>It is the overall movement of any particles from a region of higher concentration to a region of lower concentration . </li></ul><ul><li>Until an equilibrium is reached (i.e. both regions have equal conc.) </li></ul>higher conc lower conc down the conc. gradient
  4. 4. Applications of Diffusion <ul><li>Exchange of gases between alveoli in the lungs and blood </li></ul><ul><li>Exchange of gases between the leaf and atmosphere </li></ul><ul><li>Absorption of minerals by root hair cells </li></ul><ul><li>Exchange of gases by all living cells and surrounding fluid. </li></ul><ul><li>And many more!! </li></ul>
  5. 5. QuickCheck 1 <ul><li>State a condition necessary for diffusion to take place. </li></ul><ul><li>Predict what you will observe ( Hint: Iodine molecules are smaller than starch molecule ). What process is involved? </li></ul>starch solution iodine solution
  6. 6. Osmosis <ul><li>It is the overall movement of water molecules only from a region of higher water potential to a region of lower water potential , through a partially permeable membrane . </li></ul><ul><li>Until an equilibrium is reached (i.e. both regions have equal water potential) </li></ul>higher water potential lower water potential down the water potential gradient
  7. 7. Osmosis water conc. sugar solution <ul><li>Which direction do the water molecules move? </li></ul><ul><li>What happens to the liquid level in the capillary tube? </li></ul><ul><li>What happens to the liquid level in the beaker? </li></ul>Capillary tube water molecule sugar molecule Visking tubing (partially permeable membrane)
  8. 8. Osmosis 70% starch solution 10% starch solution <ul><li>Which direction do the water molecules move? </li></ul><ul><li>What happens to the liquid level in the capillary tube? </li></ul><ul><li>What happens to the liquid level in the beaker? </li></ul>Capillary tube water molecule starch molecule Visking tubing (partially permeable membrane)
  9. 9. Effect of Osmosis in Plant Cell In solution of lower water potential Water leaves the cell. Cell shrink and becomes flaccid (plasmolysis). Tough cell wall retains its own shape. In solution of same water potential No net gain or loss of water. Cell remains the same . In solution of higher water potential Water enters the cell. Vacuole expands and exerts a pressure ( turgor pressure ) against the cell wall. Cell expands and becomes turgid . Cell wall prevents the cell from bursting .
  10. 10. Effect of Osmosis in Animal Cell In solution of same water potential No net gain or loss of water. Cell remains the same . In solution of higher water potential Water enters the cell. Cell expands and burst due to absence of cell wall . In solution of lower water potential Water leaves the cell. Cell shrinks and becomes crenated .
  11. 11. Applications of Osmosis <ul><li>Intake of water by root hairs and all other cells </li></ul>
  12. 12. QuickCheck 2 1(a) Predict whether each potato strip will become shorter or longer. 1(b) Arrange the size of the potato strips from shortest to longest. 8% sugar solution 3% sugar solution 15% sugar solution potato strips of 5% sugar solution A B C
  13. 13. Active Transport <ul><li>It is the overall movement of molecules from a region of lower concentration to a region of higher concentration . </li></ul><ul><li>Energy is needed and is obtained from respiration .(mitochondria of cells) </li></ul><ul><li>Until an equilibrium is reached (i.e. both regions have equal concentration) </li></ul>higher conc lower conc up the conc. gradient
  14. 14. Applications of Active Transport <ul><li>Intake of minerals by root hairs from the soil </li></ul><ul><li>Absorption of digested food substances by the ileum (small intestine) </li></ul>
  15. 15. Surface area to Volume ratio <ul><li>The larger the surface area to volume ratio of a cell, the faster the rate at which substances move into and out of a cell. </li></ul><ul><li>Some cells are modified to increase surface area for the absorption of substances </li></ul><ul><ul><li>Root hair cells have long and narrow protrusions </li></ul></ul><ul><ul><li>Red blood cells have a flattened, biconcave shape </li></ul></ul>
  16. 16. Think… <ul><li>Do sports drinks have higher, lower or the same water potential as the cells of your body? Why?? </li></ul><ul><li>Why is it not advisable to add too much fertiliser around the roots of plants? What can be done to counter the over-addition of fertilisers? </li></ul>

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