1.  What does regulation mean?  Infer how the loss of regulation of the cell cycle may cause a problem.

3.  Cell growth and divisions are controlled  Not all cells move through the cell cycle at the same rate  Muscle and nerve cells don’t divide once they have developed  Skin, digestive and bone marrow cells grow and divide rapidly

4.  What happens to the rate of cell division if you get a cut?  How do your cells know when to stop dividing?

5.  When cells come into contact with other cells, they respond by not growing.  If cells are removed, cells will divide to fill the empty space.  Thus, controls on cell growth and division can turn on or off.

6.  When an injury occurs, cells at the edges of the injury are stimulated to divide rapidly.  When healing nears completion, the rate of cell division slows down, controls of growth are restored, and everything returns to normal.

7.  What “tells” cells when to divide, duplicate their chromosomes, or enter another phase of the cycle?  When a protein was injected into a nondividing cell, it caused mitotic spindles to form and different levels of this protein were discovered at different times in the cell cycle.  They called them cyclins, because they regulate the timing of the cell cycle

8.  Cyclins (cell cycle regulating proteins) were just the beginning of regulators discovered.  Two types of regulator proteins:  Internal regulators  External regulators

9.  Proteins that respond to events inside the cell.  For example: one protein may make sure that a cell doesn’t enter mitosis until all chromosomes have replicated.  For example: another protein may make sure all chromosomes are attached to spindle before entering anaphase.

10.  Proteins that respond to events outside the cell.  Direct the cell to slow down or speed up the cell cycle.  Some are growth factors: stimulate growth and division (embryo development and wound healing), molecules on surface slow down or stop cell cycles to prevent excessive growth and keep tissues from disrupting each other.

11.  Cancer: cells lose the ability to control growth or don’t respond to signals that regulate cell growth.  Tumor: cancer results in masses of cells that damage surrounding tissues.

12.  Have you ever heard the phrase “The cancer has spread?” Why is that a problem?  Cancer cells can break loose from tumors and spread throughout the body, disrupting normal activities by creating more tumors and causing serious medical problems or even death.

13.  Causes:  Chemicals, such as smoking tobacco  Radiation exposure  Viral infections  With all cancers, the control over the cell cycle has been broken down and lost!

15.  Surgery: Removal of localized tumors that have not spread.  Radiation: Destroying cancer cells with energy waves  Drug Therapy (Chemotherapy): Chemicals destroy the cancer cells (and the normal cells too)  Compare the causes of cancer to the treatments of cancer.