Transcript Cell Growth
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