5 3 Regulation of the Cell Cycle KEY

5. 3 Regulation of the Cell Cycle KEY CONCEPT Cell cycle regulation is necessary for healthy growth.

5. 3 Regulation of the Cell Cycle When is mitosis a good thing? • When you have to add or replace cells – growth & development – repair – replacement

5. 3 Regulation of the Cell Cycle Internal and external factors regulate cell division. • External factors include physical and chemical signals. • Growth factors are proteins that stimulate cell division. – Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.

5. 3 Regulation of the Cell Cycle Regulation of Cell Cycle Check points at each phase

5. 3 Regulation of the Cell Cycle Cells will not divide if… • there are not enough nutrients to support cell growth • DNA is damaged • DNA has not been replicated …cell will be repaired / destroyed.

5. 3 Regulation of the Cell Cycle • Two of the most important internal factors are kinases and cyclins. • External factors trigger internal factors, which affect the cell cycle.

5. 3 Regulation of the Cell Cycle • Apoptosis is programmed cell death. – a normal feature of healthy organisms – caused by a cell’s production of self-destructive enzymes – occurs in webbed fingers development of infants

5. 3 Regulation of the Cell Cycle When is mitosis a BAD thing • When cells reproduce & they are not needed – these cells take over organs, but don’t do the right job – they just keep making copies – cancer - damages organs

5. 3 Regulation of the Cell Cycle Cell division is uncontrolled in cancer. • Cancer cells form disorganized clumps called tumors. – Benign tumors remain clustered and can be removed. – Malignant tumors metastasize, or break away, and can form more tumors. normal cell cancer cell bloodstream

5. 3 Regulation of the Cell Cycle • Cancer cells do not carry out necessary functions. • Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.

5. 3 Regulation of the Cell Cycle Growth of a tumor

5. 3 Regulation of the Cell Cycle Healthy Cells • grow in a single • layer • stop dividing when they receive messages from neighbouring cells • Cancer Cells do not respond to messages from neighbouring cells…continue to divide start to grow in multiple layers that form a tumor

5. 3 Regulation of the Cell Cycle Why would cells just make copies? • If DNA gets damaged, cells stop listening to correct instructions – mutations • Causes of mutations: u u UV radiation chemical exposure radiation exposure heat u u cigarette smoke pollution age genetics

5. 3 Regulation of the Cell Cycle Tumors • Benign tumor – abnormal cells remain at original site as a lump – most do not cause serious problems & can be removed by surgery

5. 3 Regulation of the Cell Cycle Tumors • Malignant tumor – cells leave original site - carried by blood system to other tissues - start more tumors – damage functions of organs throughout body

5. 3 Regulation of the Cell Cycle Watch how a tumor grows. . . http: //www. hhmi. org/biointeractive/media/angiogenesislg. mov

5. 3 Regulation of the Cell Cycle • Carcinogens are substances known to promote cancer. • Standard cancer treatments typically kill both cancerous and healthy cells.

5. 3 Regulation of the Cell Cycle side effects Treatments for cancers • Treatments kill rapidly dividing cells – chemotherapy - poisonous drugs that kill rapidly dividing cells – radiation - high energy beam kills rapidly dividing cells