Download Cell Growth and Division

Ch. 10
Why are cells so
small?????????
DNA Overload – larger cells place more
1.
demands on the DNA.
Exchanging Materials – diffusion of materials
takes time.
2.
◦
As the ratio of surface area to volume gets small,
the cell membrane has trouble diffusing materials
fast enough.
Cell Size
Surface Area (length x
width x 6)
Volume
(length x width x height)
Ratio of Surface Area to
Volume


As a cell grows, if it doesn’t do something
about these two problems the cell will die…..
So before this occurs, the cell divides.
◦ This prevents DNA overload and increases surface
area for diffusion of materials.
10-2



Asexual reproduction
Growth and development
Repair and maintenance


Genetic information (DNA) within the nucleus of
each cell..
The number of chromosomes is species specific.
◦
◦
◦
◦
◦
◦
◦
◦
◦
Hedgehog – 88
Chicken – 78
Horse – 64
Humans = 46
Rat – 42
Starfish – 38
Snail – 24
Koala - 16
Fruit flies = 8

The genetic information must be copied
before cell division.
◦ This process is called replication.

This insures each daughter cells gets a full
set of genetic information.
◦ Without this the cell could not survive.

The “life cycle” of a cell. Two main phases.
◦ Interphase = period of time between divisions;
growth and preparation for division. Longest
phase.
◦ M phase = cell division. Shortest phase. Two parts:
 Mitosis (karyokinesis) – nuclear division
 Cytokinesis – cytoplasmic division
Section 10-2
G1 phase
M phase
S phase
G2 phase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase

The cell membrane pinches in.

A cell plate forms.
Onion Root Tip
http://www.youtube.com/watch?feature=playe
r_embedded&v=VGV3fv-uZYI
http://www.youtube.com/watch?v=aDAw2Zg4I
gE&feature=player_embedded
http://www.youtube.com/watch?v=pOsAbTi9t
Hw&feature=player_embedded

Mitosis produces two genetically identical
cells.
◦ THEY HAVE THE SAME # AND TYPE OF
CHROMOSOMES.
◦ THEY HAVE THE SAME GENETIC INFORMATION
(GENES).
◦ THERE IS NO GENETIC VARIATION. THEY ARE
CLONES.

http://nobelprize.org/educational_games/me
dicine/2001/cellcycle.html
10-3

Not all cells have the same length cell cycle…
◦ Nerve and muscle cells – very long; rarely divide
◦ Skin and blood cells – short; often divide
What controls the length of the
cell cycle??????

Contact inhibition –
◦ When cells come in contact with each other, they
usually stop growing.
◦ Cells at the site of an injury lose contact inhibition
and begin growing.
 This repairs the injury.
Section 10-3

Cyclins – proteins that regulate the timing of
the cell cycle in eukaryotic cells.
◦ Internal regulators – proteins that allow the cell
cycle to proceed in response to events going on in
the cell.
◦ External regulators – proteins that speed up or slow
down the cell cycle in response to events outside
the cell.
Section 10-3
The sample is
injected into a second
cell in G2 of
interphase.
A sample
of
cytoplasm
is
removed
from a cell
in mitosis.
As a result, the
second cell enters
mitosis.

Cancer – a disorder in which cells do not
respond to normal regulatory signals.
◦ Cancer cells have no contact inhibition.
◦ Cancer cells divide uncontrollably and produce
masses called tumors.
 Benign tumors no longer are growing.
 Malignant tumors are currently growing and may
spread.

Cancer therapy involves chemotherapy,
radiation treatments and surgical removal.

Carcinogens – agents that cause the
development of carcinomas (tumors).
◦ Radiation – x-rays, uv rays
◦ Chemicals – cigarette smoke, asbestos
◦ Genetics

Cancer therapy involves chemotherapy,
radiation treatments and surgical removal.