1. Diffusion

2. Solutions SolventSolvent – liquid SoluteSolute - solid that is dissolved SolutionSolution – liquid with dissolved substances SolubleSoluble – can dissolve Substances may be soluble in  water, eg ions, oxygen, carbon dioxide  oils, mainly small non-polar molecules

3. Diffusion net movement of particles from a region of high concentration to a region of low concentration. In other words: Molecules in a gas or liquid will tend to spread out as much as possible

4. nutrients and gases Cells need nutrients and gases for photosynthesis, respiration and other metabolic processes excrete waste products Cells excrete waste products which could become toxic if they accumulate Why do cells need transport

5. Transport mechanisms Passive transport (doesn’t require energy)  Diffusion  Facilitated diffusion  Osmosis  Filtration Active transport (uses energy from ATP)  Active transport  Bulk transport } Movement down a concentration gradient

6. 1. Diffusion increase The following will increase diffusion: 1.Steep concentration gradient 2.Larger surface area 3.Thin permeable membrane 4.Small, non-polar molecules 5. Higher temperatures

7. Convolutions increase SA:V Volume = 12 Surface area = 14 SA:V = 1.17 Volume = 12 Surface area = 26 SA:V = 1.86

8. Volume = 12 Surface area = 14 SA:V = 1.17 Volume = 1 Surface area = 4 SA:V = 4 Small organisms have a larger SA:V ratio

9. Limitations to cell size Volume = 1cm 3 SA = 6cm 2 SA:V = 6 Volume = 8cm 3 SA = 24cm 2 SA:V = 3 Nutrients can diffuse to all parts of cell fast enough to maintain life Lower SA:V Takes too long for nutrients to diffuse to all parts of cell?

10. O 2 – Non-polar CO 2 – Polar but very small H 2 O – Polar but very small Diffuse rapidly

12. Transport mechanisms Passive transport (doesn’t require energy)  Diffusion  Facilitated diffusion  Osmosis  Filtration Active transport (uses energy from ATP)  Active transport  Bulk transport } Movement down a concentration gradient

13. 2. Facilitated diffusion Membrane impermeable to molecules such as Glucose, sodium ions & chloride ions. Carrier proteins can “carry solute across” OR Ion channels act as hydrophilic pores http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_dif fusion_works.htmlhttp://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_dif fusion_works.html

14. Facilitated transport

16. Chemicals diffusing through the air Remaining slides are extras

17. Kinetic movement Molecules have kinetic energy, so they move constantly and randomly.

18. Molecules move down a concentration gradient HIGH  LOW CONCENTRATION.

19. Small molecules diffuse faster

20. Higher temperatures  more energy  faster diffusion

21. Equilibrium - still moving, but no net movement

22. AS Biology, Cell membranes and Transport 22 Diffusion of Bromine

23. AS Biology, Cell membranes and Transport 23 Diffusion of Bromine

24. Diffusion http://www.youtube.com/watch?v=H7QsDs8ZRMI http://www.youtube.com/watch?v=H7QsDs8ZRMI (5min)

25. Concentration gradients higher concentration lower concentration Molecules diffuse DOWN a concentration gradient

26. O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 High oxygen concentration O2O2 O2O2 O2O2 Lower oxygen concentration The bigger the difference, the steeper the gradient

27. Molecules diffuse more easily across thin barriers O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 Membrane thickness