Download Cell Growth and Division

Why do Cells divide?
• Growth of tissue
• Cell repair
• When you get a cut, where does the “new
skin” come from?
Cell Growth
Rather than increase in size, cells must
divide
1. To avoid DNA “overload:” Too many
chromosomes would result in mutations
2. Keep exchange of materials through the
cell membrane efficient:
3. How fast water, food, and oxygen are
transported through the cell membrane
depends on size and volume of the cell
Surface Area to Volume Ratio
• Cells favor a large Surface Area to volume
ratio
• The larger the surface area to volume
ratio, the easier it is for the cell to transport
materials in /out of the cell
Size of Cells
• Are adult and baby cells the same size?
• Yes!
• If mice cells are transplanted into an
Elephant will they get bigger?
• It depends, but yes!
Controls in Cell Growth
• Heart & nerve cells rarely divide once
they are mature
• Skin & digestive tract cells divide
constantly to replace shedding or injured
cells
• This is programmed by the cell cycle
which is controlled by DNA
Mitosis
• Process in which body cells divide to
produce two genetically identical
(daughter) cells is known as cell division.
• It is asexual reproduction
• Somatic Cells are all body cells
• The only cells that do not do mitosis are
sex cells produced in ovaries and testes.
Mitosis terms
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Body cells have a total of 46 chromosomes
They are paired so we have how many pair?
23!
We represent 23 PAIRS as 2n
If we had a total of only 23 it would be just n
We call a total of 23 pairs Diploid, 2n
Mitosis -Diagram of Chromosomes
WS in packet
Mitosis terms-Diagram of key cell
terms during mitosis
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Chromatin DNA that resembles a
ball of yarn
Centrioles -microtubules connect
to …
Centrosomes- region of
microtubules
Spindle Fibers -connect to
chromosomes from Centrioles
Poles -regions on end of cell
regions. Spindle fibers connect to
them
Metaphase plate -area where
chromosomes line up to divide
Cleavage furrow -forms during
Telephase. Where cytoplasm
divides in the new cells.
Pole
The Cell Cycle
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There are 3 main stages
1. Interphase, the cell prepares for
division.
– A. 90% of the cells time is spent in this
phase.
CELL GROWTH PHASE
1. INTERPHASE
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cy
cle_works.html
Consists of 3 steps
G1-The cell grows,
making additional
organelles &
cytoplasm
S-DNA replicates
G2-Cell will make
anything additional
needed for division
MITOSIS is Stage 2 and has 4 PHASES
http://bcs.whfreeman.com/thelifewire/content/chp09/0902001.html
• 2. Mitosis
• The cell goes through 4 phases to reproduce a
duplicate body cell
• The phases are:
• Prophase
• Metaphase
• Anaphase
• Telophase
Phases of Mitosis
Early Prophase
Late Prophase
Stage 3 CYTOKINESIS
• Creation of new cytoplasm that divides the
cell into 2 new ones.
Plant cell mitosis
Animal cell mitosis
Uncontrolled Cell Growth
Teacher’s Domain Cell folder how cancer grows
http://www.pbs.org/wgbh/nova/cancer/grow_flash.html
• Cancer is a form of uncontrolled cell growth
• The check points that the cell goes through may
no longer work
• If this occurs, then a tumor may form
• It can be non-cancerous which is called benign
• Or if it has spread metastasized