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 Unit 4
LT1
Use the diagram to help you to explain why surface area-to-volume (s.a./vol) ratios are important to a dividing cell.
•
When cells divide, their surface area (supply of nutrients
2
across the plasma membrane) decreases slower, by length
while volume (metabolic demand) decreases faster by
3
length .
•
Mitotic cell division gives the cell a much more favorable
surface area to volume ratio.
Mrs. Loyd 
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# Unit 4
LT1
Create a model to illustrate how prokaryotic DNA is divided for cell reproduction.
What is this process called?
How are the two cells related to each other genetically?
The model presented in class used two large rubber bands twisted together to represent the
circular DNA of a prokaryotic cell.
•
They adhere to the plasma membrane at the equator of the plasma membrane.
•
As cytokinesis occurs, the two rings of DNA are pulled apart into their half of the cell.
•
Two cells are formed this way. It is called binary fission. (“2” – “separating”)
•
They are genetically identical (except for the plasmid DNA that was divided by chance).
Mrs. Loyd 
[email protected]
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Unit 4
LT2a
# Identify the phases of the cell cycle.
• the long, round arrow
• the short, split arrow
• each of the five pie wedges
• the name for the resulting cells
Please do not mark on this paper.
daughter cells Mrs. Loyd 
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Unit 4
LT2c
# Put the following descriptions of each the events of each of the phases in the proper chronological order.
Cytoplasm is divided by the
“purse-string mechanism”
in animal cells and by creating
a cell plate in plant cells.
Nuclear information is arr
anged and divided.
.
anded
ble-str
u
o
d
e
s ar
r
o s o me
r large
Chrom dria divide
rane fo
b
n
o
m
h
e
c
Mito
dds m anelles.
o ws : a
g
ease.
Cell gr ne-bound or nd ATP incr
a
a
r
s.
memb f monomers for readines
o
t
in
ly
o
Supp
heckp
es a c
Includ
Chromosomes ar
e single-stranded
.
Mitochondria divid
e
Cell grows: adds
m em brane for
larger membran
e-bound organe
lles.
Supply of monom
ers and ATP
increase.
Includes a chec
kpoint for readin
ess.
DNA
Prot is repli
c
ein
prod ated
uctio
n an
dm
etab
olism
on “
hold
.”
1. Chromosomes are single-stranded.
Mitochondria divide
Cell grows: adds membrane for larger membrane-bound organelles.
Supply of monomers and ATP increase.
Includes a checkpoint for readiness.
2. DNA is replicated
Protein production and metabolism on “hold.”
3. Chromosomes are double-stranded.
Mitochondria divide
Cell grows: adds membrane for larger membrane-bound organelles.
Supply of monomers and ATP increase.
Includes a checkpoint for readiness.
4. Nuclear information is arranged and divided
5. Cytoplasm is divided by the “purse-string mechanism” in animals and by creating a cell plate in plant cells.
Mrs. Loyd 
[email protected]
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Unit 4
LT2d
Cancer is considered
a disease of the cell
cycle.
Explain why.
Cancer cells divide out of control. They
are not governed by the chemical
messages that control the cell cycle.
Sometimes, mutations cause the loss of
expression of the p53 or guardian angel
gene/protein which protects the individual
by destroying cancerous cells.
If this is then followed by a mutation for
over-expression of the “divide” command
(the Ras gene/protein), the cell becomes
cancerous and divides until a tumor forms.
Mrs. Loyd 
[email protected]
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