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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.