Transcript Do Now - Montville.net

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