1. Cell Specialization

2. Unicellular Organism – consists of only one cell - that one cell carries out all functions required to maintain the life of the organism Multicellular Organism – consists of more than one cell -Cells are specialized to perform certain functions (cell specialization/differentiation)

3. Examples of Cell Specialization 1.Neuron (nerve cell) -sends info from one part of the body to another - very long and thin

4. Examples of Cell Specialization 2.Red Blood Cells -carry oxygen throughout body -flattened disks so that they can easily flow through blood vessels

5. Examples of Cell Specialization 3.Sperm Cell -fertilizes egg -strong tail for quick swimming, distinct head for entering egg cell

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

7. 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

8. Stem Cell Research stem cells – cells of humans that can develop into different cell types

9. 2 kinds:embryonic and adult some researchers believe that they can be a source of replacement cells to treat disorders (ex. Parkinson’s disease and burn injuries) Embryonic stem cells Adult stem cells

10. Cell Communication -Cells communicate with one another by secreting and receiving chemicals -Chemicals released by one cell can influence the activity of another cell http://learn.genetics.utah.edu/content/begin/cells/cellcom/

11. Example of Cell Communication -Sensory cells to nerve cells to muscle cells http://bcs.whfreeman.com/thelifewire/content/chp46/46020.html

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

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

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

15. Negative Feedback

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