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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

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

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 Cycle

http://www.cellsalive.com/mitosis.htm

http://www.johnkyrk.com/mitosis.html
Main Events of a Cell Cycle

Interphase




G1,
S
G2
M Phase




Prophase
Metaphase
Anaphase
Telophase
http://www.cellsalive.com/mitosis.htm
Interphase

The cell grows and
replicates its DNA
 Chromosomes are
not visible, only
chromatin
Prophase

Chromatin condenses
into chromosomes
 Centrioles separate
 Nuclear envelope
breaks down
Metaphase
 Chromosomes
line
up across the center
of the cell
Anaphase

Chromosomes are
pulled apart by
spindle into
individual
chromatids
Telophase
 Chromosomes
gather at
opposite ends of the cell
 Two new nuclear
envelopes form
http://www.johnkyrk.com/mitosis.html
Cytokinesis
 The
cytoplasm pinches in
half
 Plants lay down a cell
plate
 Two new cells now exist.
Label the stages #7
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.
Which chemicals regulate the cell
cycle?
How do cells respond to contact
with other cells?
How are cancer cells different from
other cells?