1. Cell Specialization and Communication

2. Unicellular Organism one cell does everything to keep alive (protist, paramecium, amoeba)
Multicellular Organism – Cells are specialized to perform certain functions (cell specialization/differentiation)

3. Examples of Cell Specialization
Neuron (nerve cell)
Red Blood Cells
White Blood Cells
Sperm Cells
Egg Cells
Etc.

4. Cell differentiation is a result of different gene expression.

5. Most cells in your body have the same DNA
Cells use only the DNA that they need; the rest is inactive
For example, skin cells use the DNA that codes for melanin (a skin pigment that protects from UV light)
Heart cells do not need melanin, so it is “turned off” in heart cells

6. Stem Cell Research

7. Cell Communication
Cells communicate with one another by secreting and receiving chemicals
- Chemicals released by one cell can influence the activity of another cell

8. Example of Cell Communication
- Sensory cells to nerve cells to muscle cells

9. Cell Communication (cont.)
Hormone – communication chemicals that travel through the blood (ex. insulin, estrogen)
- Secreted by endocrine glands

10. Acts much slower than nerve impulses but effects last much longer
Only influence the action of target cells that have specific receptors

11. Two Hormone Mechanisms
1. Negative Feedback – the end product stops the production of the hormone

12. Negative Feedback

13. Positive Feedback – the last step triggers more release of the initial hormone or other hormones
- triggers a series of events