Download Inkyung-biological investigations - LabScience9

In Kyung LEE
Lab Science 9 (Mr. Happer)
Biological Investigations
Pg. 1
Is exchanging materials hard for big cells?
Goal
The goal of this experiment is to see whether or not exchanging materials is hard for big
cells. To determine this, I will use cubes (made out of potato) as models of the cells, and
dyeing as the materials getting in the cell.
Expectations
I expect that big cubes have less dyeing parts than small cubes.
The volume increases much more rapidly than the surface area, casing the ratio of
surface area to volume to decrease.
Variables
Independent variable: 1cm cube, 2cm cube, and 3cm cube
Dependent variable: dyeing part of the three cubes
Materials: a beaker, dyeing, a weighing machine, a heating machine, a potato
Procedure
In Kyung LEE
Lab Science 9 (Mr. Happer)
Biological Investigations
Pg. 2
1. Cut the potato into 1cm cube, 2cm cube, and 3cm cube by knife.
Be careful when using knife.
2. Put dyeing and water into the beaker.
(200mL of water and about 150 drops of food dyeing)
3. Put the cubes into the beaker and boil them for 15 minutes.
In Kyung LEE
Lab Science 9 (Mr. Happer)
Biological Investigations
Pg. 3
Be careful when using heating machine.
4. Cut the dyed parts of the cubes and measure them
Results
Total weight
Weight of
dyed parts
Percentage
1cm
2cm
3cm
0.15g
3.90g
16.70g
0.15g
2.54g
8.44g
100%
65.13%
50.54%
The smaller the cube is, the faster it got dyed.
Analyze
1cm cube
2cm cube
3cm cube
Surface
Area
1cmx1cmx6
=6cm2
2cmx2cmx6
=24cm2
3cmx3cmx6
=54cm2
Volume
1cmx1cmx1cm
=1cm3
2cmx2cmx2cm
=8cm3
3cmx3cmx3cm
=27cm3
Ratio
6/1=6:1
24/8=3:1
54/27=2:1
Looking at the table above, you will notice that the volume increases much
more rapidly than the surface area, causing the ratio of surface area to volume to
decrease. The result of this experiment was the smaller the cube is, the faster it got dyed.
This means that the ratio to surface area to volume will decrease.
The cells exchange materials, such as waste products or nutrients, through cell
membrane. As organisms grow, cells inside them also grow. However, we do not see
big cells in big people and small cells in small people. Why does this happen?
One of the reasons why there are cell divisions is when the cells grow and the
volume of the cell increases much rapidly than the surface area, cells have trouble
exchanging materials. My experiment shows that this is true. Imagine that the cubes I
used were cells and the food dyeing was nutrients. When I cut the biggest cube into half,
In Kyung LEE
Lab Science 9 (Mr. Happer)
Biological Investigations
Pg. 4
after boiling it, I noticed that the inside part of the cube was not dyed—only the surface
was dyed, meaning that big cells have difficulty getting in nutrients in.
However, this is not the only reason why cells divide. The larger a cell becomes,
the more demands the cell places on its DNA. To help understand why this happens, let
us compare the cell to a class. Suppose your science teacher, Mr. Happer, has two
different class—one with five students and another with thirty students. In the first class,
he would be able to help all of the students while they are doing their biology
experiment. He would even have some spare time. In the second class with thirty
students, though, he would have no time to help all the students. Mr. Happer would be
busy, trying to help all thirty students at one time.
Now, imagine that Mr. Happer is DNA of the cell and the class is the cell. The
bigger the cell is, the harder DNA can control. Before it becomes too large, a growing
cell divides forming two “daughter” cells. The process by which a cell divides into two
new daughter cells is called cell division.