Transcript Ertertewt ertwetr - Campbell County Schools

Cell Growth and Division
10-1 Cell growth
Biology
Mr. Hines
A living thing will grow by making more
cells.
Cells of an adult animal are about the same
size as a young animal – there are just
more of them
Limits to cell growth
Are there limits to the size in which cells can
grow?
Yes
Cells are limited in size for 2 reasons
1. DNA overload
2. Exchanging materials
DNA overload
The larger a cell gets, the more responsibility
is placed on the nucleus to control it. In
other words, the nucleus can only
effectively control a small cell.
Remember that DNA is located in the nucleus
of Eukaryotic cells – which controls the
cell.
This can be compared to a small town. If the
town grows too large, it will be harder to
manage – garbage collection, police, mail,
street cleaning, schools, jails, grocery
store.
It is easier for a large town to divide into 2
smaller towns.
This is the same for cells – Cells will divide
and each new cell will have its own
nucleus.
Exchanging materials
Remember from earlier that all cells need to
get nutrients into them; food, water, oxygen,
etc.
Cells must also get rid of waste.
This happens through the cell membrane.
The area of the membrane that surrounds the
cell is called ‘surface area’
The amount of materials that a cell can get
inside of it will depend on the size of the
surface area.
The amount of materials that a cell uses
depends on its volume.
In order to understand this concept, you must
understand the relationship between
surface area and volume.
Ratio of Surface area to volume
To keep matters, simple, we will assume that a
cell has the shape of a cube.
Calculating the surface area of a cube.
Lxwx6
Calculating the volume of a cube
Lxwxh
Surface Area / Volume Ratio
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One 4-cm cube
Eight 2-cm cubes
Sixty-four 1-cm cubes
 All three have the same volume, but the group
on the right has four times the surface area.
Section 10-1
Cell Size
Surface Area
(length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area
to Volume
Ratio of Surface Area to
Volume in Cells
Notice that the volume increases more quickly
than the surface area.
Since the surface area is responsible for
getting nutrients in and out of the cell, a
growing volume presents serious problems
to a large cell.
In other words, a large cell can not get
nutrients in and out fast enough.
This can be compared to a small town with
one main road.
Once the town starts growing, the road
becomes jammed up which causes difficulty
getting supplies in and out of the town.
So what does this mean?
This means that as a cell grows too large, the
surface area to volume ratio causes the
cell to have difficulties getting nutrients in
and out of the cell.
Division of the Cell
Before the cell becomes too large, it divides
into 2 daughter cells.
Each daughter cell will have its own nucleus,
DNA, as well a complete set of organelles
This process is called cell division.
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