1. Exchange with the Environment Cell Transport

2. Cell Processes For a cell to survive, it must get nutrients and water. It must also get rid of wastes How can the cell get materials in and out through the cell membrane?

3. Cell membrane Made up of a phospholipid bilayer and several proteins Phospholipid: Hydrophillic phosphate head Hydrophobic fatty acid tail Image from: http://academic.brooklyn.cuny. edu/biology/bio4fv/page/phos phb.htm

4. Cell membrane

5. Cell membrane: Proteins Integral Proteins Embedded in lipid bilayer Receptor proteins and transport proteins Transmit signal or materials into/out of the cell Peripheral Proteins Only on one side of membrane Some act as enzymes Some act as cell markers

6. Fluid mosaic model of cell membrane Phospholipid bilayer acts as a fluid Lipids and proteins can move in the layer Sterols (including cholesterol) are used to help keep membrane structure

7. Cell membrane

8. Cell Membrane

9. Diffusion The movement of particles from an area of high concentration to an area of low concentration down the concentration gradient Occurs outside of cells and across cell membranes

10. Diffusion Picture from: http://hyperphysics.phy- astr.gsu.edu/hbase/kinetic/diffu s.html

11. Osmosis The diffusion of water across a cell membrane If solution outside a cell has more water than the cell then water will move into the cell

12. Osmosis Image from: http://hyperphysics.phy- astr.gsu.edu/hbase/kinetic/diffus.ht ml#c3

13. Movement of small particles Not all particles are able to slip through a cell membrane through diffusion Example: sugars and starches aren’t small enough to move between the phospholipid molecules

14. Types of solutions Isotonic Has same concentration as a cell, the cell neither loses nor gains water Hypotonic Has less concentration than cell, cell gains water

15. Types of solutions Hypertonic Has more concentration than cell, cell loses water

16. Osmosis in cells Paramecia Control water flow by using a contractile vacuole Collect excess water and pump it out of the cell Plant cells Live in hypotonic environment Survive because of cell wall Pressure of water against cell wall: turgor pressure Too much water leaves the cell: plasmolysis Water storage in Central Vacuole

17. Transport of particles Some particles have to go through “doorways” to enter the cell Because they are too large or not soluble through cell membrane These “doorways” are protein channels These proteins are carrier proteins

18. Facilitated Diffusion Diffusion of particles through protein channels in a cell membrane Particles move from high concentration to low concentration Example: glucose and salts Does NOT require energy

19. Image from: http://www.bios.niu.edu/sims/metabolism/meta bolism1.htm

20. Ion Channels Allow ions to move across the cell membrane Specific to specific ions Some are “gated”

21. Active transport Movement of particles against the normal direction of diffusion Particles move from LOW concentration to HIGH Requires energy from the energy molecule ATP Example: sodium/potassium pump

22. Image from: http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/images/u1fig7a.jpg

23. Image from: http://www.sp.uconn.edu/~terry/images/anim/antiport.gif

25. Moving larger particles Endocytosis Cell membrane surrounds a particle, and encloses it in a vesicle Phagocytosis When large particles are taken in by endocytosis Pinocytosis Transport of fluids or solutes

26. Image from: http://ww w.sirinet.n et/~jgjohn so/endocy tosissmall.jpg

27. Endocytosis Image from: http://www.sp.uconn.edu/~bi1 07vc/images/cell/clathrin.jpg

28. Exocytosis Used to remove large particles from the cell Vesicles formed at the ER or Golgi move to the cell membrane for release

29. Exocytosis Image from: http://www.sirinet.net/~jgjohnso/exocytosis.jpg

30. Image from: http://cellbio.utmb.edu/cellbio/end7.jpg

31. Modeling the cell membrane