cell growth and division 10-1 cell growth biology mr. hines
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Cell Growth and Division
10-1 Cell growth
Biology
Mr. Hines
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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
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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
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DNA overloadThe 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.
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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.
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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’
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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.
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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.
L x w x 6
Calculating the volume of a cube
L x w x h
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Surface Area / Volume Ratio
All three have the same volume, but the group on the right has four times the surface area.
One 4-cm cube Eight 2-cm cubes Sixty-four 1-cm cubes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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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 CellsSection 10-1
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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.
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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.
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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.
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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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