1. Cells and Their Environment

2. Cells interact with their environments!

3. What separate the cell from everything else (its surroundings)? Alternate Animation

4. These phospholipids are always moving! This movement creates space for some very small particles to slide through (i.e. O 2, CO 2 ) Watch them move! Want more detail? What makes up the membrane?

5. There are also proteins embedded into the lipid bilayer These are transport proteins (Transmembrane proteins) ◦ Span across both layers and help in transporting particles that are too big to fit through the gaps in- between phospholipids.

6. Types of Transport Passive Transport ◦Diffusion ◦Facilitated Diffusion ◦Osmosis Active Transport ◦Endocytosis ◦Exocytosis ◦Sodium-Potassium Pump

7. Concentration Gradient - difference in concentrations across space or a membrane ◦When particles diffuse across space or a membrane, we say they “go down(with) their concentration gradient.” The gradient can help you decide whether its active or passive transport!

8. Passive Transport Passive Transport – movement of a substance down(with) its concentration gradient across the cell membrane. Does not require energy! For example: ◦A biker going downhill ◦Students leaving class at the end of the hour ◦i.e. Simple diffusion, osmosis, facilitated diffusion

9. Simple Diffusion Diffusion – movement of matter from an area of high concentration to an area of low concentration No energy is required! HighLow

10. (Dynamic) Equilibrium is reached when particles become equally distributed across space This is the goal! Dynamic systems try to establish equilibrium!

11. Facilitated Diffusion Facilitated Diffusion – a type of passive transport that requires a protein to “facilitate”(help) the substance across the membrane by changing shape Uses no energy! See it!

12. Active Transport The transport of a substance across the cell membrane against its concentration gradient (from low to high) Uses energy! For example ◦Sodium-Potassium Pump ◦Exocytosis ◦Endocytosis

13. See it! Sodium-potassium pump Membrane protein specific to sodium and potassium ions Moves 3 sodium ions (Na+) out of the cell and 2 potassium ions (K+) into the cell against their concentration gradient Uses energy!

14. Endocytosis Process used by cells to take in large biomolecules from the outside by engulfing it with their cell membrane

15. Exocytosis process by which a cell releases large biomolecules through the cell membrane

16. See it!

17. Osmosis A special kind of diffusion Uses no energy! When water diffuses across a semi (selectively) – permeable membrane (like the cell membrane!) The movement of water is not regulated by transport proteins Osmosis is affected by the concentration of other substances in and outside of the cell. See it!

18. Cell Environment Vocab Hypertonic Environment – when there is a higher concentration of solutes outside of the cell ◦water will move out of the cell See it happen!

19. Hypotonic Environment – when there is a lower concentration of solutes outside of the cell ◦water will move into the cell See it happen!

20. Isotonic Environment – when there is an equal number of solutes on the inside and outside of the cell ◦net water movement into and out of the cell will be equal See it happen!

22. Let’s think about it… Why can’t we drink ocean water? ◦Hypertonic Environment ◦Red Blood cells would shrink, be dehydrated

23. Cell Environment Vocab SOLUTES SUCK!!! Water, that is. (think of salt)

24. Review Options The Cell Membrane: Review and quiz yourself Review of Passive Transport Animation showing hypotonic and hypertonic Review of Active Transport