Cells divide for three main reasons: 1) Cells cannot grow indefinitely and must divide to avoid becoming inefficient as they increase in size. As cells grow larger, their surface area to volume ratio decreases making it harder to absorb nutrients and remove waste. 2) Cells must repair or replace damaged cells to maintain healthy tissues and organs. 3) Multicellular organisms require cell division for reproduction and growth of the overall organism as it develops.

1. Cells and SystemsWhy do cells divide?

2. Why do cells divide?because they cannot grow any largerto repair or replace damaged cellsfor reproduction or growth

3. Thinking with modelsAssume a cell is a cube

4. 6 μm21 μm3624 μm28 μm3396 μm264 μm31.5

5. As cell size increases, both the volume and surface area increaseVolume increases at a faster rate – this is shown by a steeper slope on the trend line.

7. As cell size increases, the surface to volume ratio decreasesThis means that in larger cells there is not as much membrane surface area for the amount of cytoplasm as there is in smaller cells

8. Why Do Cells Divide? Think about . .

9. Why Do Cells Divide?Because the volume of a growing cell increases faster then its surface areaCells that grow too large no longer have enough surface area to take in nutrients and remove wasteCells that grow too large take longer to move materials within the cellAs cells grow larger they become more inefficient

10. Why Do Cells Divide?Some cells die or are damaged, they must be replacedMulticellular organisms need to grow and develop, to do this requires more cells

11. How Do Cells Divide?

12. What is cancer?The cell cycle is a controlled process of growth and divisionSometimes the control mechanisms break down. Usually this is due to a mutation in cell DNACancer is a disease that develops when this happens. Cells grow and divide uncontrollably. This can result in tumors and invasion of other healthy tissue.