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Do Now!!
1.
2.
What happens to your body when you get a cut?
Explain in your own words what happens when you
get cut and the healing process
Chapter 9
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
o Why must cells divide?
o Take a look at the following cells…
o Which cell do you think will work most efficiently?
Surface Area vs. Volume
Surface Area
(length x width) x 6 sides
Volume
length x width x height
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
Do Now!!
Think-Pair-Share
1) 2 X 2 X 2
2) 8 x 8 X 8
3) 4 X 4 X 4
If you had 3 cells with the
dimensions on the left…
Which cell has the largest
surface area to volume ratio?
What benefit does this cell
have?
Cellular Division
Cell division occurs in all organisms:
Performs different functions
Unicellular organisms (ex: bacteria):
Binary fission: division into 2 identical
Binary fission
cells (clone)
Multicellular organisms (ex: US!):
Mitosis
Mitosis
Cell Cycle Purposes
Growth
Cells are limited in size
Development (specialized cells)
Repair
Repair
Specialized Cells
The Cell Cycle
2 main phases:
1.
2.
Interphase
M Phase
o Cells vary in cell
cycle times
Cell Cycle
All cells start out in Interphase
They then enter cell division, Mitosis &
Cytokinesis
Do Now!!
Mitosis/Cytokinesis
Mitosis: Nuclear
Division
Cytokinesis:
Cytoplasm division
Mitosis
1.Prophase
2.Metaphase
3.Anaphase
4.Telophase +
Cytokinesis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
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
Move to poles of cell
Attach to the spindle fibers
Prophase
The cell’s chromatin condenses
Sister chromatids
are attached at
the centromere
Spindle apparatus* forms in the
cytoplasm:
Attach to sister chromatids
The nuclear envelope and
nucleolus disappears
*Spindle apparatus:
Centrioles (centrosome)
Aster
Spindle fibers
Metaphase
Sister chromatids 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 of the spindle apparatus begin
to shorten
The sister chromatids separate (pulled 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
Cleavage
Furrow
Do Now!!
If a cell has 40 chromosomes in G1 phase, how
many chromosomes will the daughter cells have?
How many chromosomes will that cell have in
G2 phase?
Draw a cell with 4 chromosomes in metaphase!
Cytokinesis
In animal cells, microfilaments constrict, or pinch, the
cytoplasm
They create a “cleavage furrow”
2 new and identical cells are formed!
Cytokinesis
In plant cells, a new structure, called a cell plate, forms:
Will become the cell wall
Divides the cells
2 new and identical cells are formed!
Let’s Review!
http://highered.mcgraw-
hill.com/sites/0072437316/student_view0/chapter11/
animations.html
Do Now!!
Label the parts of the cell.
What phases of mitosis are they in?
Cell Cycle Regulation
Normal Cell Cycle:
Different cyclin
/ CDK (cyclin
dependent kinases) combinations
signal other activities
These include:
DNA replication
Protein synthesis
Nuclear division (mitosis)
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, division will stop
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 (cont.)
UV Light
Causes skin cancer
(most common type
of cancer)
Tanning beds linked
to “melanoma”deadliest type of
skin cancer.
Carcinogens (cont.)
Pesticides
Overexposure has been
known to cause leukemia
and lymphoma.
Inherited cancers
Some cancers are inherited through mutated genes that
“turn on” the cancer
Ex: BRCA1 gene (mutation can cause breast cancer)
Most cancers
are sporadic: genetic changes over time
Cancer Cells vs. Normal Cells
Cancer cells lack density-dependent
inhibition,
causing cells to pile up on top of each other
They are “immortal”:
divide an infinite number of times
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