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Cell Cycle. Cell Growth and Division. 2. Why do cells divide?. If the cell is too big: Too much demand is placed DNA Harder to move enough nutrients and wastes across the cell membrane. Surface area vs. volume. 4. Surface Area vs. Volume.

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Cell cycle

Cell Cycle

Cell Growth and Division


2 why do cells divide
2. Why do cells divide?

  • If the cell is too big:

    • Too much demand is placed DNA

    • Harder to move enough nutrients and wastes across the cell membrane



4 surface area vs volume
4. Surface Area vs. Volume

  • As a cell increases in size, volume increases faster than surface area

  • This causes the ratio of surface area to volume to decrease.

  • This is a serious problem for the cell and is why the cell cannot grow any larger than it does.


5 cell division solves those problems
5. Cell division solves those problems

  • Before a cell becomes too large, a growing cell replicates its DNA and then divides into two new “daughter” cells. This is called mitosis.


Cell cycle1
Cell Cycle

  • http://www.cellsalive.com/mitosis.htm

  • http://www.johnkyrk.com/mitosis.html


Main events of a cell cycle
Main Events of a Cell Cycle

  • Interphase

    • G1,

    • S

    • G2

  • M Phase

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase

  • http://www.cellsalive.com/mitosis.htm


Interphase
Interphase

  • The cell grows and replicates its DNA

  • Chromosomes are not visible, only chromatin


Prophase
Prophase

  • Chromatin condenses into chromosomes

  • Centrioles separate

  • Nuclear envelope breaks down


Metaphase
Metaphase

  • Chromosomes line up across the center of the cell


Anaphase
Anaphase

  • Chromosomes are pulled apart by spindle into individual chromatids


Telophase
Telophase

  • Chromosomes gather at opposite ends of the cell

  • Two new nuclear envelopes form


Cytokinesis

Cytokinesis

  • The cytoplasm pinches in half

  • Plants lay down a cell plate

  • Two new cells now exist.



What stops cell from growing
What stops cell from growing?

  • Proximity to neighbor cells.

    • Cells in a petri dish will continue to grow until they come into contact with other cells.

    • Similarily, skin around a wound.





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