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Cell division

Cell division. The cell membrane is semi-permeable and all nutrients and wastes must pass across it to get into or out of the cell. As a cells grows, it requires more supplies: nutrients and oxygen and needs to get rid of more waste like CO 2 .

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Cell division

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  1. Cell division

  2. The cell membrane is semi-permeable and all nutrients and wastes must pass across it to get into or out of the cell. As a cells grows, it requires more supplies: nutrients and oxygen and needs to get rid of more waste like CO2. As the cell gets bigger, the volume increases faster than the surface area of the membrane The distance inside the cell gets bigger too! Why do cells need to divide?

  3. As cells increase in size, the volume grows faster than the surface area.

  4. At a certain size, there is not enough surface area for nutrients/wastes to cross that is required by the cell So a cell divides into smaller cells in order to allow enough surface area to suit its needs

  5. Growth – grow from a single cell to trillions of cells. Maintenance – replace dead/worn-out cells Repair – heals damaged tissues (e.g. cut or broken bone) 3 Functions of cell division

  6. That’s a lot of skin cells to replace!

  7. Why? There is only one nucleus! Each chromosome / DNA strand is different with different instructions on it. The Cell Cycle makes sure that new cells have the same DNA in them. One cell produces two identical cells A cell cannot just break in two!

  8. The Cell cycle Growth Stage / Interphase Cell grows. Makes new organelles. Makes a duplicate copy of all the DNA inside the nucleus

  9. Cell Division includes a multistep process called MITOSIS. 1 cell before it divides is called the parent cell. The 2 new cells are called daughter cells. A cell cannot just break in two!

  10. Handout – describe the phases of cell division.

  11. Interphase Prophase Metaphase Anaphase Telophase Cytokineseis – division of the cytoplasm Stages of the cell cycle MITOSIS I – PMAT – C for short IPrefer Mice And Talking Cats

  12. Cell grows DNA duplicates – 2 copies DNA in strands called chromatin (not visible) Interphase (Growth phase)

  13. Nucleus dissolves DNA condenses (coils) into visible chromosomes Chromosomes are identical pairs attached at centre prophase

  14. Chromosomes are pushed together to the middle of the cell by fibres. metaphase

  15. Identical chromosomes are pulled apart towards opposite ends of the cell by the fibres. anaphase

  16. Two new nuclei form around the chromosomes at the ends of the cell. DNA starts to uncoil into chromatin again telophase

  17. Dividing of the cytoplasm Cell membrane “pinches” to form the 2 new daughter cells. cytokinesis

  18. Cytokinesis in a human kidney cell

  19. http://www.cellsalive.com/mitosis.htm Mitosis is a continuous process – it doesn’t pause at each step!

  20. Onion root tips grow very quickly – RAPID cell division Under a microscope, they are excellent for locating cells in all stages of the cell cycle – including all 4 phases of mitosis.

  21. The following slides show pictures of mitosis in onion tip cells. From the pictures, determine which stage of mitosis are depicted. What is the evidence for each choice? Which Stage of Mitosis is This?

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