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Do Now
1.
What happens to your body when you get a
cut?
2.
Make a drawing illustrating the healing
process.
Cellular Division
Objectives
1.
To understand why cells divide.
2. To explain different limitations on cell size.
3. To summarize the steps of the cell cycle.
Cell Size
*Take a look at the
following cells…
*Which cell do you
think will work most
efficiently?
Surface Area vs. Volume
L x W x # of sides
LxWxH
Practice…

Find the SA:V ratio for the three cubes above.

Which cube has the higher SA:V ratio?
Size Limitations

Key factor that limits cell growth is ratio of
surface area to volume

As the cell grows, its volume increases
much more rapidly than the surface area.

Cell can have difficulty supplying nutrients
and expelling waste products.
Transport of Substances

Substances enter
membrane through
diffusion

Diffusion over a large
distance = slow

Smaller cells are
more efficient!
Cell Communication

The need for signaling
proteins to move
throughout the cell
also limits cell size.

Cell size affects the
ability of the cell to
communicate
instructions for cellular
functions.
Cell Cycle
Varies between 8 minutes and one year
 Average 12-24 hours

Cell Cycle
All cells start out in Interphase
 They then enter cell division, Mitosis &
Cytokinesis

Interphase
A. G1 Phase:
 First growth phase
 The cell is growing, carrying out
normal cell functions, and
preparing to replicate DNA.
B. S Phase:
 DNA is copied (DNA
Replication)
C. G2 Phase:
 Second Growth Phase
 Proteins needed for cell division
are produced
 The cell prepares for the
division of its nucleus.
Mitosis/Cytokinesis
 Mitosis: Nuclear Division
 Cytokinesis: Cell Division
Do Now
Do Now

Please hand homework in the bin.

Grab a piece of construction paper from
my desk. (Color doesn’t matter)

Then sign into Kahoot.it using the game
code on the board.

This will be done individually.
Important Vocab.

Chromosome Tightly coiled DNA

Chromatid Half a replicated Chromosome

Chromatin loosely coiled DNA

Centromere Center of a chromosome where the sister chromatids attach

Centriole Organize the microtubules
 Attach to the spindle fibers
MITOSIS
Prophase

Nucleolus disappears

Nuclear membrane breaks apart

The cell’s chromatin tightens
making chromosomes visible!

Sister chromatids are attached at
the centromere.

Spindle apparatus forms and
attaches to centromeres of
chromosomes.
Metaphase

Sister chromatids (duplicted chromosomes) are pulled
along the spindle apparatus toward the center of the
cell.

They line up in the middle of the cell at metaphase
plate.
Anaphase
The microtubules (spindle fibers) of the spindle
apparatus begin to shorten.
 The sister chromatids separate (apart).
 The chromosomes move toward the poles of
the cell.

Telophase
The chromosomes arrive at the poles and begin
to relax.
 Two new nuclear membranes begin to form and
the nucleoli reappear.
 The spindle apparatus disassembles.

Cytokinesis

Cytoplasm will divide forming two new genetically
identical daughter cells.

In animal cells, microfilaments constrict, or pinch, the
cytoplasm. They create a “cleavage furrow”

In plant cells, a new structure, called a cell plate, forms
( which will eventually become the new cell wall)
Quick Review – Place Cells in Mitosis Order
A
B
D
C
E
Let’s Review!

http://highered.mcgrawhill.com/sites/0072437316/student_view0
/chapter11/animations.html
Do Now
Label the parts of the cell.
 What phases of mitosis?

9.3 Cell Cycle Regulation

Normal Cell Cycle:
 Different cyclin / CDK (cyclin
dependent kinases)
combinations signal other
activities
 These including
○ DNA replication
○ Protein synthesis
○ Nuclear division
Quality Control Checkpoints
The cell cycle has built-in checkpoints
 These monitor the cycle and can stop it if
something goes wrong.
 Spindle checkpoints also have been identified
in mitosis.

 Ex. If no spindle fibers – will stop before cytokinesis
Cell Cycle Checkpoints

*If G1 checkpoint shows cell is not ready for DNA
replication, it enters G0 phase and will not divide.*
When Cell Division Goes Wrong
Begins as a single cell that undergoes
“transformation” (process converting a
normal cell into a cancer cell)
 Immune system fails to destroy cell.
 Cell proliferates and forms a tumor.

Transformation
Transformation is caused by mutations.
 Mutations can result from a variety of different
“carcinogens” (things that cause cancer)

Carcinogens
 Tobacco
 “Dip” : contains
28 known
carcinogens.
 Cigarettes
Carcinogens
UV
Light
 Causes skin cancer
(most common type
of cancer)
 Tanning beds linked
to “melanoma”deadliest type of
skin cancer.
Carcinogens
 Pesticides
 Overexposure
has been
known to cause
leukemia and
lymphoma.
Cancer Cells vs. Normal Cells

Cancer cells lack density-dependent inhibition, causing
cells to pile up on top of each other

They proceed past checkpoints

They are “immortal”, meaning they can divide an infinite
number of times, whereas nomral cells divide only
about 20-50 times before stopping.
Tumors

Benign tumor
 Abnormally growing mass of cells
 Can disrupt certain organs, ex: brain, if they get too
big
 Can be completely removed with surgery

Malignant tumor
 Spreads into neighboring tissues
 Can metastasize, enter blood and lymph vessels, and
spread to other organs and parts of the body
Types of Cancer

Carcinomas
 Originates in external or internal “coverings” such as
skin or the lining of the intestine

Sarcomas
 In tissues that support the body such as bone and
muscle

Leukemias and lymphomas
 In blood-forming tissues such as bone marrow,
spleen, and lymph nodes.
Cancer Genetics

Multiple changes in DNA are needed to cause
cancer

Cancer increase with age

Certain cancers are inherited in certain families
(chances to have it)
Do Now
What is the difference between a benign tumor
and a malignant tumor?
 What category of cancer is found on the lining
of different organs?

Apoptosis
Programmed cell death
 Cells going through apoptosis actually shrink
and shrivel in a controlled process.

 Ex. Leave in Fall
 Ex. Webbed Fingers/Toes
 DNA Damaged Cells
Stem Cells

Unspecialized cells
that can develop
into specialized cells
when under the right
conditions
Stem Cells (cont)
Embryonic Stem Cells
Adult Stem Cells
•After fertilization, the
resulting mass of cells
divides repeatedly until
there are about 100–150
cells.
•Found in various tissues in
the body and might be
used to maintain and repair
the same kind of tissue
•These cells have not
become specialized.
•Less controversial
because the adult stem
cells can be obtained with
the consent of their donor
http://www.stemcellresearchfacts.com/definition.html
Stem Cell Controversy

http://www.youtube.com/watch?v=27skh7prkN0
&feature=related
As a review…

Draw out all of the phases of mitosis with
colored pencils. Use 4 chromosomes