Transcript Cellular Division

Do Now
1. What happens to your body
when you get a cut?
2. Make a drawing illustrating
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
*Take a look at the
following cells…
*Which cell do you
think will work most
efficiently?
Surface Area vs. Volume
(2 x L x W) + (2 x L x H) + (2 x H x W)
LxWxH
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!
Think-Pair-Share
1) 3 X 2 X 2
2) 6 x 1 X 1
3) 3 X 6 X 1
• 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?
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
• Cell division prevents the cell from
becoming too large.
• It also is the way the cell reproduces so
that you grow and heal certain injuries.
• Cells reproduce by a cycle of growing
and dividing called the cell cycle
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.
Genetic Material
= CHROMATIN
Mitosis/Cytokinesis
• Mitosis: Nuclear Division
• Cytokinesis: Cell Division
Do Now
Review
• Surface area : Volume :: _________ : _______
(Cell Parts)
Which cell has a bigger surface area to
volume ratio?
2x3x2
OR
4x1x1
What benefit does this cell have?
MITOSIS
MITOSIS
• Label and order
the cells from 1
–5
• What are the
differences
between plant
and animal
cells during
division?
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
Prophase
• The cell’s chromatin tightens
• Sister chromatids are attached
at the centromere.
• Spindle fibers form in the
cytoplasm.
• The nuclear envelope seems
to disappear.
• Spindle fibers attach to the
sister chromatids.
Metaphase
• Sister chromatids are pulled along the spindle
apparatus toward the center of the cell.
• They line up in the middle of the cell.
Anaphase
• The microtubules 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
• 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.
Let’s Review!
• http://highered.mcgrawhill.com/sites/0072437316/student_vie
w0/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
Quiz Study Guide…
• Cell Cycle
– Interphase (G1, S, G2)
– Mitosis (PMAT)
– Cytokinesis
•
•
•
•
•
•
Phases of Mitosis
Cell Regulation (CDK, Checkpoints, and cyclins)
Cancer
Stem Cells
Apoptosis
Cell Volume VS. Surface Area Ratio
As a review…
• Draw out all of the phases of mitosis with
colored pencils. Use 4 chromosomes