Cell Growth
Section 10-1
Limits To Cell Growth
There
are two main reasons
why cells divide
DNA OVERLOAD: The
larger a cell becomes the
more demands the cell places
on its DNA
EXCHANGE OF
MATERIALS: The larger a
cell becomes the more
trouble it has moving enough
nutrients and wastes across
the cell membrane
DNA Overload
 All
of the information that
controls a cell’s functions is
stored in the DNA
When a cell is small the
information stored in the
DNA is able to meet the
cell’s needs
As a cell increases in size
the DNA can not keep up
with all of the demands
which are placed on it
DNA Overload Cont.
If
a cell were to
grow without limit an
“information crisis”
would occur
Exchanging Materials
Food,
oxygen, and water
enter the cell through the
cell membrane
Waste products leave in
the same way
The rate at which this
exchange of materials
takes place depends on the
surface area of the cell
This
is the total area of the
cell membrane
Exchanging Materials Cont.
 However
the rate at which
food and oxygen are used up
and waste products are
produced depends on the
volume of the cell
 Understanding the
relationship between a cell’s
volume and its surface area
is the key to understanding
why cells must divide
Surface Area To Volume Ratio
 The
volume of a cell increase
much more rapidly than the
surface area
 As
a result the ratio of surface area
to volume ratio decreases
 Surface area = l x w x 6 sides
 Volume = l x w x h
A
cell will have increasing
difficulty moving oxygen and
nutrients into the cell and moving
waste products out as it
increases in size.
Cell Division
A
cell will divide into two
cells before it reaches the
point of DNA overload or
the exchange of material
becomes a problem
The process is called cell
division
The
two cells that result are
called “daughter cells”
because they are identical to
one another
Cell Division Cont.
Before
cell division occurs
the cell replicates or copies
all of its DNA
The replication of DNA
solves the problem of
information storage
Each daughter cell gets
one complete set of
genetic information
Cell Division Cont.
Cell
division also solves
the problem of increasing
size by reducing the cells
volume
Each daughter cell has an
increased ratio of
surface area to volume
This
allows for efficient
exchange of materials with
the environment