1. CELL SPECIALIZATION Chapter 7 Section 4 EQ: Why do cells in multicellular organisms become specialized?

2. Some cells send signals Most are chemical signals ◦ hormones ◦ neurotransmitters Target cells receive the signal ◦ Have receptors either on outer side of cell membrane or inside cell (if signal can cross membrane)

3. Receiving Signals Receptor proteins ◦ Bind only signals that match specific shape of its binding site ◦ Once signal molecule binds to receptor site  receptor protein changes shape  which relays “message” to the target cell

4. Responding to Signals The cell may respond to a signal by: ◦ Changing its membrane permeability ◦ Activating enzymes ◦ Causing a second messenger to form ◦ Second messenger is a molecule that is generated when a specific signal attaches to a receptor protein; it causes a change in cell function

5. Neurotransmitter Serotonin

6. Animation http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::5 35::535::/sites/dl/free/0072437316/ http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::5 35::535::/sites/dl/free/0072437316/

7. CELL SPECIALIZATION Stem Cells: type of cell that gives rise to all types of cells in that organ system During embryonic development, cells not only increase in #, but also undergo differentiation becoming specialized in structure & function

9. Cell Differentiation

11. Cell Specialization Columnar Cells Cuboidal Cells

12. Squamous Cells Neurons

13. Why do some cells become neurons & others become red blood cells?

14. Different genes are “turned on” so specialization happens