1. Exchange of materials

2. Cells exchange matter and energy In: Oxygen Nutrients eg glucose (carbon dioxide and light energy in plants) Water Ions Out: Carbon dioxide Wastes eg urea (oxygen in plants) Water Ions Heat energy Processes: Respiration Synthesis Growth Division Photosynthesis (in plants)

3. Exchange of material Occurs at the cell membrane Involves the intake of essential materials eg nutrients and oxygen and the removal of unwanted materials eg wastes The processes involved include diffusion, osmosis and active transport

4. Structure of the cell membrane Fluid mosaic model Describe the roles of: Phospholipids Waterproof barrier, acts as a bubble, main constituent Proteins Act as carriers, receptor sites, antigens, channels Carbohydrates Act as receptor sites, antigens

5. Cell membranes Sketch a typical cell membrane according to the Fluid Mosaic model Describe the roles of: Phospholipids Proteins Carbohydrates

6. Cells Sketch a typical cell membrane according to the Fluid Mosaic model. Describe the roles of: Phospholipids = A – waterproof, flexible layer, that lets in small particles Proteins = B – provides channels for larger particles (facilitated diffusions), acts as pumps (active transport), acts as receptor sites Carbohydrates = C - acts as receptor sites A B C

7. Exchange of material Small particles eg water, ions can pass through the gaps between the phospholipids Larger molecules pass through channels in the proteins or are carried by special proteins

8. Terminology Solution Solute Solvent Permeable Differentially permeable Hypotonic Hypertonic Isotonic Mixture of solvent and solute Thing added to solvent Liquid to which solute is added Allows substances to move through Allows some substances to move through, but not others Less concentrated (dilute) More concentrated Concentrations are equal

9. Movement through membranes

10. Movement of particles - diffusion Occurs without energy Particles will move from higher concentrations to lower concentrations

11. Diffusion through membranes Membranes are differentially permeable Permeable substances (eg small particles) Impermeable substances (eg large particles) Movement is Energy Move through Can’t move through From areas of high concentration to areas of low concentration Is not needed

12. Facilitated diffusion Allows larger or less permeable substances to cross Involves channel proteins Energy is not needed

13. Osmosis Movement of water This occurs from areas of high water concentration (low concentration of solute) to areas of low water concentration (high concentration of solute)

14. Concentration gradient This refers to the difference in concentration across membranes The steeper the gradient, the greater the movement Osmotic pressure refers to the pull of water due to concentration gradients

15. Active transport Movement against a concentration gradient. Energy is needed

16. Ion pumps Involves special proteins that act as pumps Allows cells to maintain ion concentrations that are very different from the external environment Energy is used

17. Endocytosis Movement due to folding of membrane and bringing in the trapped substances Energy is needed Phagocytosis – solid substances trapped Pinocytosis – liquids are trapped

18. Exocytosis Movement due to vacuoles moving to membrane and attaching to release contents Energy needed

19. Does size matter? As size increases: What happens to volume? What happens to surface area? What happens to surface area to volume ratio? decreases increases

20. Surface area and volume 2 Size1x1x12x2x23x3x34x4x4 Surface area 6245496 Volume182764 SA: Vol6:13:12:11.5:1 Size of sides 10 234 Surface area volume SA:Vol 1 2 3 4 5 6 7 1 20 30 40 50 60 70 80 90 100 50

21. Affect of shape on surface area and volume Calculate the volume and surface area for these: 2x 2x2 1x1x8 4x2x1 8 cubic units 24 square units 28 square units 34 square units

22. How cells increase their surface area Size Shape Folding Cell extensions pseudopods microvilli