1. Movement of Molecules Revision

2. Movement across Membranes All cells must be able to take in and expel various substances across their membranes in order to survive, grow and reproduce Cells do this via a number of different processes……

3. Diffusion Is the net movement of a substance from a region of high concentration to a region of low concentration. Movement occurs down a concentration gradient No energy is required.

4. Osmosis Is the movement of water particles from a region of high water concentration (low solute) to a region of low water concentration (high solute). No energy is required Movement occurs down a concentration gradient

5. Concentration of Solutions Hypertonic: has a higher concentration of dissolved substances than the cell or solution that it is being compared to Isotonic: has the same concentration of dissolved substances as the cell or solution it is being compared to Hypotonic: has a lower concentration of dissolved substances than the cell or solution that it is being compared to

6. Surrounding Fluid Animal CellPlant cell Isotonic solutionWater moves in and out at same rate Water moves in and out at the same rate Hypotonic solutionWater enters the cell causing it to swell Water enters the cell and unto the vacuole causing it to swell. The membrane pushes against the cell wall. The cell is turgid. Hypertonic solutionThere is movement of water out of the cell. The cell decreases in size. There is movement of water out of the cell. Cell contents decreases in size. The cell wall keeps the shape. Plasmolysis.

7. IsotonicHypotonicHypertonic

8. Facilitated Diffusion Channel Mediated Some substances need to move through protein channels in membrane. Carrier Mediated Some substances need a protein carrier in addition to a protein channel. Neither require energy and both occur down a concentration gradient.

9. Active Transport Is the movement of substances from a region of low concentration to a region of high concentration Energy is required as movement is against a concentration gradient. Carrier molecules assist the movement

11. Bulk Transport Endocytosis: bulk transport of material ______ a cell Exocytosis: bulk transport of material ______ of a cell

12. Question Time!

16. Why do cells need diffusion? For survival… Cells obtain nutrients such as oxygen and glucose Cells excrete wastes as carbon dioxide and urea

17. Surface Area: Volume Ratio The surface area of an object in comparison to it’s volume. Important for the movement of substances The LARGER the SA:V ratio the FASTER the rate of exchange.

18. Why are cells so small? To enhance the rate at which molecules are exchanged across the cell membrane If cells were large diffusion would occur at such a slow rate that the cell would not be able to survive So, cells are miniscule

19. Transport Systems Multicellular organisms do not rely on diffusion alone Transport systems such as the circulatory system enables cells to have a ready supply of nutrients and oxygen Transport systems also enable an organism to excrete wastes at an efficient rate

20. Question Time! Explain the difference in size between the Little Penguins on coastal Victoria and the Emperor Penguins from Antarctica. __________________________________ __________________________________ __________________________________ __________________________________ __________________________________ __________________________________ __________________________________