Diffusion: The diffusing effect of sucroseGarcia Govea, Diana CeciliaMayo 2013 / 2106-030

PRACTICAL WORK: FERMENTATIONBIOLOGY SLDiana Cecilia Garcia Govea[footnoteRef:1]Candidate number: 2106-030Examination Session: May 2013 [1: I hereby declare that I am the author of this work and I have not received help other than the allowed by the International Baccalaureate. I have properly cited the words, ideas or graphics from other sources, .regardless if they have been expressed in written, oral or visual form.]

Diffusion:The diffusing effect of sucrose at concentrations of 20%, 30%, 40%, 50% and 60% on 0.03 gram Hydrogel Balls

Introduction/ AbstractDiffusion refers to the process by which molecules intermingle as a result of their kinetic energyof random motion.[footnoteRef:2] It is understood as the passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration.[footnoteRef:3] [2: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html] [3: http://www.biology-online.org/dictionary/Diffusion]

Simple passive diffusionoccurs when small molecules pass through the lipid bilayer of a cell membrane.Facilitated diffusiondepends on carrier proteins imbedded in the membrane to allow specific substances to pass through, that might not be able to diffuse through the cell membrane.[footnoteRef:4] [4: http://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htm]

At all temperatures above absolute zero, the individual atoms that constitute any substance are always in movement. Indeed, the amount of this movement is what constitutes temperature itself. When this movement becomes large enough, the bonds holding the atoms of a solid together break, and the substance becomes either liquid or gaseous. These gaseous or liquid atoms can move more freely, since they are no longer bound to their nearest neighbors.[footnoteRef:5] [5: http://physioweb.uvm.edu/diffusion/]

Although the movement of individual particles is undirected and unpredictable, we can nevertheless make predictions about the behavior of groups of particles. If the particles are not evenly distributed, then at least two regions exists: one with higher concentration of particles and the other with a lower concentration. Such a difference in the concentration of a substance from one place to another establishes a concentration gradient.In diffusion, the random motion of particles results in their net movement down their own concentration gradient, from the region of higher concentration to the one of lower concentration. This does not mean individual particles are prohibited from moving against the gradient. However, because there are initially more particles in the region of higher concentration, it logically follows that more particles move randomly from there into the low-concentration region than the reverse. Thus, if a membrane is permeable to a substance, there is net movement from the side of the membrane where it is more highly concentrated to the side where is less concentrated. Such a gradient across the membrane is a form of stored energy. Stored energy is potential energy, which is the capacity to do work as a result of position or state. The stored energy of the concentration gradient is spontaneous. For this reason, movement down a concentration gradient is spontaneous. Diffusion occurs rapidly over very short distances. The rate of diffusion is determined by the movement of the particles, which in turn is a function of their size and shape, their electric charges, and the temperature. As the temperature rises, particles move faster and the rate of diffusion increases. Particles of different substances in a mixture diffuse independently of one another. Diffusion moves solutes toward a state of equilibrium. If particles are not added to or removed from the system, a state of dynamic equilibrium is reached. In this condition, the particles are uniformly distributed and there is no net change in the system. Particles continue to move back and forth across the membrane, but they move at equal rates and in both directions. [footnoteRef:6] [6: Solomon, Eldra, Linda Berg , and Diana W. Martin. Biology. Cengage Learning, 2010. 116-117. eBook. 2.866081). Also, and most importantly, the P-value, which is the probability that the null hypothesis (that there is no difference between any of the data sets) is true. If the value of P is higher than 5%, then there is no significant difference between any of the data sets, meaning that the null hypothesis is true; but if the value of P is lower than 5% then at least one of the groups is significantly different from the others. In this case, the P value (2.32E-18) is much lower than 5%, meaning that at least one of the groups is different from the others. We can see that the variance of sucrose at 20% and sucrose at 60% are similar to each other, but very distant from sucrose at 40% and 50%, while 30% is the odd one out. With these explained, we can reject the null hypothesis. This establishes that the rate of diffusion is dependent of concentrations of sucrose. Therefore, rate of diffusion, taken by the increase of the weight of the hydrogel balls, is dependent of the concentration of sucrose.

Data Presentation

Graph 1.1 Averages of the total growth of the hydrogel balls after diffusing the different sucrose concentrations with the interval confidence as the error bars, and a linear trendline, as well as the equation and R value displayed; done using Microsoft Excel. R value analysis:0: No correlation1: Strong positive correlation-1: Strong negative correlation

The previous graph displays the averages of the total growth of the hydrogel balls after being soaked in different sucrose concentrations (20%, 30%, 40%, 50% and 60%) for 75minutes, causing a diffusing effect on them. The number of each average is displayed so there is no confusion. The error bars were done taking in account the interval of confidence, as we can see they are really small (sucrose at 30% being the longest) this is because, as we stated before, the data calculated is reliable and close to the real data. The linear trendline displays an inversely proportional growth to the increase of concentration. This is because, as we also stated before, the higher the sucrose concentration, the less amount of water present, therefore the less diffusion possible for the hydrogel balls. The R value displayed states a strong positive correlation, since 0.9374 is very close to 1 (the perfect correlation). This further supports the hypothesis that rate of diffusion, observed through the growth of the hydrogel balls in each sample is dependent of the concentration of sucrose.

Errors/UncertaintyTaking in account the 0.01 uncertainties in the electronic laboratory scale, along with the possible minor error in the measurements and weightings made, it can be said that the rate of uncertainty is small, and that the results are almost completely true to the actual results. The possible errors are stated when necessary, for example, with the error bars that state the possible errors taken when collecting the data. Another possible error would be of human nature, perhaps when taking the hydrogel balls out of the beakers to be weighted; it may have taken a little bit longer than a microsecond to properly take the hydrogel balls out, thus letting them soak more seconds than necessary.

ConclusionsAs previously stated, hydrogel balls are hydrophilic (tend to absorb water), this means that the higher the presence of water, the more they can and will soak up. When the concentration of sucrose increases, the solution has a more solute (sucrose) and less water. If there is more solute obstructing the absorption of water, the less the hydrogel balls are going to swell up. It is by the increase in size of the hydrogel balls (caused by the soaking up of water present in the sucrose solutions) that we could properly test our hypothesis. We weighted the initial (0.03 gram hydrogel balls) and final weight of each hydrogel ball used after being soaked in different sucrose concentrations for 75 minutes; we also recorded the weight of each ball every 15 minutes.

In conclusion, when the concentration of sucrose increases (with 45mL. of sucrose concentration 60% being the maximum on this experiment) the diffusion rate observed through the growth of the hydrogel balls- decreases. This can also be understand by stating that when the concentration gradient increases (lower concentration of sucrose [C12H22O11 ] = high concentration gradient),, the rate of diffusion increases. This states an inversely proportional strong positive correlation among the dependent and independent variables.As the Tables 1.1 to 1.5 show, when the concentration of sucrose increased, the results of the total growth of the hydrogel balls decrease. As the concentration of sucrose increased, the rate of diffusion decreased. This is because when the concentration of sucrose increases, the concentration gradient decreases. When there is a higher presence of water, in other words, when the solution has less solute, the hydrogel ball has to swell up more to reach equilibrium between the two environments. Where as low solutions with low presence of water, or solutions with more solute, the hydrogel ball does not have to swell up so much. As seen in the Graph 1.1 (Average of the total growth of the hydrogel balls after diffusing the different sucrose concentrations), the growth of hydrogel balls is inversely gradual, decreasing as the sucrose concentration increases. We can also reinforce that by seeing the results of both the Anova test and the R value shown in the graph. The Anova test shows that due to the fact that P value obtained (2.32E-18) is much smaller than 5% the null hypothesis that states independence between variables can be rejected. The P value in the Anova test also shows that there is a significant variation among the data collected. The R value being 0.9374, on the other hand, states the correlation between the variables, proving a strong positive correlation among them. These test all help support the initial hypothesis that the rate of diffusion (shown by the increase of weight in the hydrogel balls) is dependent of the concentration of sucrose, decreasing when the concentration of sucrose increases. Evaluation:The experiment depended almost completely of the laboratory scale, which has an error of 0.005. This fact is very crucial, since if the hydrogel balls where not weighted correctly, the results may vary. Also, the time at which the hydrogel balls where removed for weighting may have varied by a few seconds for each sample, for it was almost impossible to get all the samples out at the exact same time. Since the experiment was done over a period of two days, the conditions, as temperature and pressure, in the laboratory may have varied. The temperature may have also been affected by the use of burners by other students in the laboratory. Some limitations to this method are that to have a completely accurate result of the weight of the hydrogel balls, you would need a very accurate and specialized scale, along with the removal of the hydrogel balls at the same exact time. Some errors that may be avoided are the accuracy of the removal of the hydrogel balls to be weighted, working in a laboratory with a controlled environment, and trying to finish the experiment in one day, to avoid changes in the environment. Works Citedhttp://www.biology-online.org/dictionary/Diffusionhttp://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.htmlhttp://physioweb.uvm.edu/diffusion/Solomon, Eldra, Linda Berg , and Diana W. Martin. Biology. Cengage Learning, 2010. 116-117. Taken from : eBook.http://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htmhttp://en.wikipedia.org/wiki/Gel#Hydrogels2