Biology Eei

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| 2012|
| Toby Rheinberger
Lab Partner: Jeremy Saba
|

[The Effect of surface area to volume ratio and solute concentration on osmosis.]| The aim of this experiment was to test the effect of surface area on osmosis and the effect of solute concentration on osmosis. To test this aim to hypotheses were devised. 1) If potato pieces are immersed in various salt solutions, then the pieces with the greatest surface area to volume ratio will experience the greatest weight change, because more water can move by osmosis across the potato cell’s semi permeable membrane. 2) If potato pieces are immersed in various salt solutions, then the pieces immersed in the most concentrated solution will experience he greatest weight change, because more water must pass across the potato cells semi permeable membrane by osmosis to achieve an equilibrium. The results from testing these hypotheses did not support either and were shown to be flawed because they did not reflect the theories of osmosis relating to surface area to volume ration and salt concentration. |

Contents
Introduction2
Figure 12
Figure 33
Figure 44
Figure 54
Figure 64
Aim5
Hypotheses5
Variables6
Independent6
Dependent6
Controlled6
Materials6
Method7
Risk Assessment7
Risk Conclusion:7
Results/ Data collection8
Surface Area to Volume Ratio8
Table 18
Table 28
Table 38
Solute Concentration8
Table 48
Table 58
Table 69
Discussion9
Conclusion:10
Bibliography11
Appendix12

Introduction
All living organisms require an even distribution of specific nutrients throughout their bodies. The distribution of these nutrients must remain constant otherwise the organism will not be able to function at full capacity, which may lead to its death. It is for this reason that osmosis and other forms of diffusion are of prime importance to all living organisms, because they influence the distribution of nutrients throughout the organism. (Fact Monster , 2007) A thorough understanding of diffusion and osmosis is therefore required by all biologists due to the crucial part it plays in the functioning of organisms. In order to attain a broader understanding of this topic this experiment was conducted to discover; the effect of surface area on osmosis and the effect of salt concentration of osmosis. Figure 1. The process of osmosis. (Huxley & Walter, 1998) Figure 1. The process of osmosis. (Huxley & Walter, 1998) Osmosis plays a crucial part in both chemistry and biology and it is therefore essential to differentiate between the two different concepts. In biology osmosis is generally defined as the movement of water, via diffusion, through a semi-permeable membrane. The water diffuses from a hypotonic solution (low concentration of solute) to a hypertonic solution.(High concentration of solute). [fig. 1] (Biology Online , 2008)

Distribution of nutrient occurs within cells because of osmosis and other forms of diffusion, but osmosis and other forms of simple diffusion are only possible because of the semi-permeable nature of the membranes that surrounds and protect cells. Semi-permeable membranes only allow select molecules, which are important to the correct functioning of the cell, to enter the cell. Semi-permeable membranes are commonly made of cellulose and were originally thought to be “a solid sheet with holes” (Plank , 2011) , however recent electron micrographs have revealed that, in fact they “look more like a sponge.” (Plank , 2011) The size of the holes within this ‘sponge’ determines the size of the molecule that is able to pass through it. [fig.2] It is in this way the semi-permeable membranes are able to select what passes in and out of the cell; ie membranes with different size holes will allow molecules of different sizes to pass into the membrane. (Plank , 2011) However the sizes of the holes within the sponge are not the only thing that affects diffusion. Membranes also...
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