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# Why do Cells Divide?

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### Why do Cells Divide?

1. 1. Cells and SystemsWhy do cells divide?<br />
2. 2. Why do cells divide?<br />because they cannot grow any larger<br />to repair or replace damaged cells<br />for reproduction or growth<br />
3. 3. Thinking with models<br />Assume a cell is a cube <br />
4. 4. 6 μm2<br />1 μm3<br />6<br />24 μm2<br />8 μm3<br />3<br />96 μm2<br />64 μm3<br />1.5<br />
5. 5. As cell size increases, both the volume and surface area increase<br />Volume increases at a faster rate – this is shown by a steeper slope on the trend line.<br />
6. 6.
7. 7. As cell size increases, the surface to volume ratio decreases<br />This means that in larger cells there is not as much membrane surface area for the amount of cytoplasm as there is in smaller cells<br />
8. 8. Why Do Cells Divide? Think about . . <br />
9. 9. Why Do Cells Divide?<br />Because the volume of a growing cell increases faster then its surface area<br />Cells that grow too large no longer have enough surface area to take in nutrients and remove waste<br />Cells that grow too large take longer to move materials within the cell<br />As cells grow larger they become more inefficient<br />
10. 10. Why Do Cells Divide?<br />Some cells die or are damaged, they must be replaced<br />Multicellular organisms need to grow and develop, to do this requires more cells<br />
11. 11. How Do Cells Divide?<br />
12. 12. What is cancer?<br />The cell cycle is a controlled process of growth and division<br />Sometimes the control mechanisms break down. Usually this is due to a mutation in cell DNA<br />Cancer is a disease that develops when this happens. Cells grow and divide uncontrollably. This can result in tumors and invasion of other healthy tissue.<br />