1. CELL BOUNDARIES The Cell Membrane and Transport Processes

2. I. The Structure and Function of the Cell Membrane

3. Components of the cell membrane:  Phospholipid bilayer – nonpolar fatty acid tails turn inside, polar phosphate heads turn outside – forms a flexible structure as a boundary  Proteins – can be integral proteins or peripheral proteins. They can act as enzymes, receptors, transport and binding molecules  Carbohydrates – Identification tags outside of the cell membrane (glycolipids and glycoproteins)  Cholesterol – helps stabilizing the membrane by making it more solid – animal cells

4. The Function of the Cell Membrane  Surrounds the cell.  Regulate the transport of molecules in and out of the cell -- semipermeable  Immune response  Attaches the cells to other cells or surfaces.  The model that describes cell membrane, the Fluid Mosaic Model  http://www.youtube.com/watch?v=GW0lqf4Fqpg http://www.youtube.com/watch?v=GW0lqf4Fqpg  http://www.youtube.com/watch?v=Qqsf_UJcfBc http://www.youtube.com/watch?v=Qqsf_UJcfBc

5.  Cell membranes control what goes in and out of the cell  It allows some substances to cross more easily than others Selective Permeability

6. II. Passive Transport Processes  Transport means the movement of molecules from one side of the cell membrane to the other  Transport is influenced by: The size of substances The polarity of substances The concentration of substances The permeability of the cell membrane

7.  Passive transport: requires no energy from the cell, the energy comes from the difference in concentration not ATP (energy from the cell).  Moves smaller substances from the higher to the lower concentration area.  Important in transporting O 2, CO 2, water, small molecules. http://bcs.whfreeman.com/thelifewire/content/chp05/0502001.html

8. Types of Passive Transport  Diffusion – moving substances within the cell and small nonpolar molecules across the phospholipid bilayer.

9. http://www.stolaf.edu/people/giannini/flashani mat/transport/osmosis.swf  Osmosis: the movement of water across the cell membrane by using the phospholipid bilayer or transport proteins.  Tonicity:  Describes the tendency of a cell in a given solution to lose or gain water.  Isotonic, hypertonic, and hypotonic

10. Osmosis in action  Isotonic solutions – when cells are put into solutions that have equivalent salt concentration, visible osmosis does not take place.  Hypotonic solutions – Cells in very dilute solutions will take in water and eventually can burst (animal cells).  Hypertonic solutions – Cells in very concentrated solutions will lose water and shrink.

12.  Facilitated Diffusion – a special type of diffusion in which the transported molecules are moved by the help of a transport protein. http://bcs.whfreeman.com/thelifewire/cont ent/chp05/0502001.html

13. III. Active Transport http://bcs.whfreeman.com/thelifewire/content/chp05/0502002.html http://bcs.whfreeman.com/thelifewire/content/chp05/0502002.html  Transport processes that can move substances from the lower concentration area to the higher by using energy.  Energy is gained by using ATP molecules.

14.  A type of active transport is the Na- K ion pump  3 sodium ions move out of the cell with the help of a transport protein, while 2 potassium ions move into the cell.

16.  H + ion pump – this active transport moves hydrogen ions (protons) from low to high concentration area by using energy from the cell (ATP).

17. IV. Bulk Transport  Bulk transport – transport of large substances through the cell membrane by using vesicles. Endocytosis – a process by which large particles can move into the cell  Types of endocytosis: Phagocytosis – engulfing solid particles Pinocytosis – engulfing liquids, solutions Receptor-mediated endocytosis – moving into the cell by first binding with receptor molecules on the cell’s surface. http://www.youtube.com/watch?v=4gLtk8Yc1Zc http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rectpr.htm

19.  Exocytosis – the process by which the cell releases large molecules through its cell membrane