1. Fun Fact! There are over 200 different types of cells in the human body, each performing specific functions!

2. Do all cells go through the cell cycle at the same rate? NO Some cells divide quickly & some divide slowly. Some types of cells do not undergo cell division at all!

3. Different types of cells divide at different rates. Skin cells & cells in the bone marrow divide rapidly.

4. Different types of cells divide at different rates. Muscle & nerve cells do not divide once they have developed. These cells remain in the G0 phase of the cell cycle (resting phase).

5. Regulating the Cell Cycle

6. Control of Cell Division Cell growth & cell division can be turned on & off. When you’re injured, your cells divide rapidly to repair the injury. When the injury has healed, the cells stop dividing.

7. Regulation of the Cell Cycle Controlling the cell cycle is necessary for healthy growth. The cell cycle is controlled by both internal & external factors.

8. Regulation of the Cell Cycle Internal regulators: signals from within the cell to regulate the cell cycle – They make sure everything is complete before moving on. Proteins called cyclins are present when the cell is dividing, but absent during interphase. Cyclins regulate the timing of the cell cycle.

10. Regulation of the Cell Cycle External regulators: stimulate or suppress cell growth by recognizing the surrounding situation – Injury repair – Embryonic stem cell differentiation If you break a bone, bone cells near the break will divide until the break is filled in.

11. Regulation of the Cell Cycle Apoptosis is programmed cell death, or “cell suicide”. – A normal feature of healthy organisms – Caused by a cell’s production of self-destructive enzymes Webbing of the fingers & toes is normal in developing infants. Before the baby is born, apoptosis occurs & enzymes destroy the extra tissues between the fingers.

12. Uncontrolled Cell Growth What happens when your cells lose control & cannot regulate their cell cycle? When cells in your body cannot control cell growth & division, cancer may form. Cancer cells cannot respond to the signals that regulate the division of cells.

13. Uncontrolled Cell Growth When cancer cells have been dividing uncontrollably, tumors form. Tumors can damage surrounding tissue. Cells from tumors can break free & travel to other parts of the body, forming new tumors.

14. Benign vs. Malignant Tumors Benign tumors do not spread to other parts of the body; they are non-cancerous. Tumors can become malignant (cancerous) & the cells can metastasize (spread to other parts of the body). – Malignant cells have a different shape than normal cells & grow very quickly.

17. Uncontrolled Cell Growth Most mammal cells form a single layer in a culture dish & stop dividing once they touch other cells. Cancer cells do not carry out necessary functions. They come from normal cells with damage to genes involved in cell cycle regulation.

18. Cancer Cancer cells tend to have a damaged oncogene. – This gene possesses the information needed to respond to internal & external regulators.

19. Carcinogens Substances known to promote cancer Some reasons that cells may lose the ability to control growth: – Smoking – Radiation Exposure – Viral Infection Scientists who study cancer research how cells divide.

20. Treatment There are several methods of treating cancer. Standard cancer treatments typically kill both cancerous cells & healthy cells. – This is why there are so many side effects.

21. Research 1 of the following with a partner: 1.Why does chemotherapy, a common treatment for cancer, result in the loss of hair? 2.What role does apoptosis play in the development of neural connections in the brain? 3.What role does apoptosis play in the development & maintenance of the human immune system? 4.What role does apoptosis play in the metamorphosis of a tadpole into an adult frog? Be specific about the types of cells involved, why it needs to occur, etc…