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5.3 Regulation of the Cell Cycle KEY CONCEPT Cell cycle regulation is necessary for healthy growth. 5.3 Regulation of the Cell Cycle Internal and external factors regulate cell division. • Internal factors: – External factors trigger internal factors, which affect the cell cycle – Two of the most important internal factors are kinases and cyclins. - Kinase-enzyme that, when activated, transfers a phosphate group from one molecule to a specific target molecule, changing its shape. Activated by cyclins. - Cyclins are a group of proteins that are rapidly made and destroyed at certain points in the cell cycle. These two factors help a cell advance to different stages of the cell cycle 5.3 Regulation of the Cell Cycle Internal and external factors regulate cell division. • External factors include physical and chemical signals. – Physical: - cell-cell contact · Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells. – Chemical: - Growth factors are proteins that stimulate cell division. 5.3 Regulation of the Cell Cycle • Carcinogens are substances known to promote cancer. – Ex: tobacco smoke, air pollutants, radiation, and even some mutated genes carried by viruses. 5.3 Regulation of the Cell Cycle Cancer cells • Characterized by uncontrolled cell division. – Continue to grow despite cell-cell contact or lack of growth factors. • Standard cancer treatments typically kill both cancerous and healthy cells. normal cell cancer cell bloodstream 5.3 Regulation of the Cell Cycle Cancer cells • Cancer cells form disorganized clumps called tumors. – Do not carry out specialized functions needed by the body. – 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 • Apoptosis is programmed cell death. – a normal feature of healthy organisms by ridding the body of unhealthy cells. – caused by a cell’s production of self-destructive enzymes – occurs in webbed fingers development of infants - EX: cells between fingers. 5.3 Regulation of the Cell Cycle YOU HAD A TAIL…AND GILL SLITS!!! 5.3 Regulation of the Cell Cycle YOU HAD A TAIL…AND GILL SLITS!!!