Passive diffusion. Name: Leo Plese School: XV. gymansium Zagreb. Research work in biology 1 st grade of high school

Transcription

1 Research work in biology 1 st grade of high school Passive diffusion Name: Leo Plese School: XV. gymansium Zagreb Leo Plese, e- mail: Plese.Leo@gmail.com

2 2 Passive diffusion Table of Contents Introduction and Hypothesis Problem Description Known Facts Related to the Problem Objective Hypothesis Materials and Methods. 7 Materials Methods Procedure Description... 8 Results Conclusion References

3 Passive diffusion 3 Problem Description Introduction and Hypothesis Problem we are going to talk about in this research work is to describe occurrence of diffusion. To describe diffusion occurrence, we will do an experiment in which we will measure electric current through the electric circuit i.e. current flow through solution of distilled water and table salt. Thanks to table salt, the solution will be electric conductor, so called electrolyte. What motivated me to explore this topic is importance of diffusion in living beings. It is e.g. very important for transportation of water and oxygen through cell membrane. Besides this, I was motivated by diffusion process itself which can be discussed both from biological but also from chemical and physical perspective. Hereby, this research work is based on biological explanation of diffusion but also contains elements of chemistry and physics. Known Facts Related to the Problem Diffusion is process of a particle's movement from area of higher concentration of the matter to area of its lower concentration. Example of diffusion is matter diffusion after removing barrier which separates two parts of a liquid with different matter concentration (Figure 1). When we talk about diffusion in living beings, we say diffusion is a form of passive matter transport through a cell membrane. In this type of diffusion, dissolved matter (solute) is spontaneously transported from area where it is in higher to area where it is in lower concentration. Thus, this type of diffusion is different from others in that it occurs in living beings and therefore it has its specialties but it is still true that solute moves from area of higher to area of lower concentration. Diffusion uniqueness in living beings is evident in special membrane two-layer cell membrane built from phospholipids (esters of glycerol alcohol which contain two molecules of fatty acids and a phosphate group) and in diffusing of molecules of some gases (oxygen, carbon dioxide, nitrogen and others), small uncharged polar molecules (water, ethanol and others) and hydrophobic molecules (e.g. benzene). Matter diffusing through cell membrane in process of passive diffusion are shown in Figure 2. Molecules diffusing in diffusion is movement of dissolved matter molecules through a cell membrane in the way that molecules firstly dissolve in cell membrane phospholipid bilayer and thereafter, when they go out from the bilayer, they get dissolved in water on the other side of the cell membrane. Molecules move from cytoplasm (intracellular) to extracellular space and vice versa (Figure 3). Diffusion described which occurs in living beings is a kind of diffusion we call simple diffusion, which is a type of passive transport. It is said passive diffusion 3

4 4 Passive diffusion is process where molecules "travel" down their concentration gradient through a membrane. Concentration gradient is a difference in concentrations of solute between the two sides of a membrane. Passive (simple) diffusion is a nonselective transport as there are transported all molecules which can transit from area of higher to area of lower concentration. Passive diffusion is also a discussion topic of this research work. Diffusion is process of one particle's penetration into particles of another matter due to random thermic motion, according to physical definition of diffusion. Here it is not a membrane separating two areas of different concentration but a barrier which is to be removed. In one of these experiments, we would use a barrier to separate a solution on two parts of different temperature and different concentrations of solute. Since there is concentration gradient, dissolved particles will go down the concentration gradient in diffusion process. Furthermore, due to thermal gradient (difference in temperature between the parts of the liquid), molecules will go down the thermal gradient. This means that molecules with greater heat will move towards those with less heat but also in opposite direction; however, more molecules will move from warmer to colder side of the solution (Figure 4). In this way in the experiment described, we could notice gradual equalization of mixture temperature and of solute concentration on both the sides of the container. In the end, concentration of solute and mixture (solution) temperature will be equal in all the parts of the solution. Figure 1. Gradual equalization of matter concentration after removing a barrier

5 Passive diffusion 5 Figure 2. Penetration of particular molecules in passive diffusion through cell membrane Figure 3. Gradual transfer of matter from extracellular into intracellular space through cell membrane Figure 4. Gradual transfer of solute particles and heat energy down their concentration and thermal gradient 5

6 6 Passive diffusion Objective The objective of this research work is to prove passive diffusion and explore its occurrence. Hypothesis I hypothesize that table salt will go through the membrane of the little container and enter water in the large container, and that current flow through the table salt and distilled water solution will increase simultaneously as in distilled water in the large container will be more and more of table salt. When majority of table salt will have gone through the membrane from the little into the large container, diffusion process will stop.

7 Passive diffusion 7 Materials and Methods Materials In Figure 5 equipment and matter used in diffusion experiment can be seen. Equipment a plastic container, a little plastic container, a piece of gaze, adhesive tape, timer, copper electrode, zinc electrode, 4.5 V battery, multimeter for measurement of current permeability through aqueous solution of table salt, scissors, 6 V 50 ma bulb, 5 wires as electric current conductors. Matter 150 cm 3 of distilled water (in plastic container), 5 cm 3 of distilled water (in little plastic container), 5 ml of table salt (containing mostly sodium chloride NaCl) Methods Tracking current flow in dependence on time using a multimeter and a timer. Recording experiment with the camera with the intention of analyzing the experiment results after its performance. Figure 5. Equipment and matter used in diffusion experiment 7

8 8 Passive diffusion Procedure Description 1. All conductors needed connect to multimeter, battery and electrodes to make an electric circuit. Also, connect a little bulb in the circuit, which plays a role of an electric load, so as to be able to measure current flow through the water. 2. Pour 5 cm 3 of distilled water into the little plastic container. Sodium and chloride ions, which make up sodium chloride, will ensure current flow through the distilled water. Thereafter, pour 5 cm 3 of distilled water in the container (Figure 6). Thus, supersaturated table salt solution is gotten. Cover the little plastic container with a layer of gaze. Glue the gaze with adhezive tape to the container. The gaze has the function of membrane in the little container. 3. Put equipment and matter prepared neatly onto a table. 4. Pour 150 cm 3 of distilled water into the (large) plastic container. 5. The little plastic container prepared dive into the water in the large plastic container. At the same moment, turn on the timer with aim of tracking current flow over time. 6. When diffusion process stops with occuring (9.90 ma), get the little plastic containet out of the water. Cut the membrane in the little plastic container. Return the container back into the water. As table salt starts to go out in greater amounts, rapid increase in current flow through the electric circuit is evident. 7. Mix the solution in the little container up to speed the current increasing up. 8. Soon after mixing the solution, weak light coming from the the bulb is noticeable. After approximately 45 seconds, the bulb glow intensifies so become strong enough to be clearly seen. This is also culmination of the experiment because at that moment current is the greatest and diffusion process the most intense after which it slowly comes to an end. Now it is time for recording and analyzing data gotten from the experiment and collected from the sources of information listed in References chapter. Experiment analysis is conducted simultaneously with watching experiment record recorded with camera.

9 Passive diffusion 9 Figure 6. Pouring 5 cm 3 of distilled water into the little container with 5 cm 3 of table salt 9

10 10 Passive diffusion Results Table and diagram of the results gotten from the experiment. Time (s) Current (ma) Description Decrease in current increasing is evident, which means diffusion of salty liquid is less and less Due to less intense diffusion, after this step we will speed diffusion up in the way we will make a greater hole in the membrane We drill the hole in the membrane We return the container with salty solution into the distilled water Rapid current flow caused by faster diffusion is evident. To speed up the process even more, mix the salty solution up Due to already sufficient current, it can be noticed the bulb begins to glow The bulb glows; pour the salty solution out and pour it into the container with distilled water The bulb glow is clearly visible. Figure 7. Tabular representation of current flow depending on time with description of key moments during the experiment performance In the first column of the table from Figure 7 particular points of time from the experiment performing are given. In the second column there are amounts of current flow at the chosen points of time of the experiment performance written. In the third column are descriptions of more important steps and observations of changes from the experiment performance.

11 Passive diffusion 11 Figure 8. Graphical representation of electric current-time dependence On the diagram's ordinate is electric current in milliamperes (ma) and on the abscissa is time in seconds (s). The diagram is made according using data from the table. It presents relation between electric current and time. From the table (Figure 7) and the diagram attached (Figure 8) we read out the amounts and changes in amounts of current over time. From the table we can read out the exact amounts of current over time, while from the graph are clearly visible ranges of slight and rapid current flow changes. Simultaneously with describing current flow changes, we can notice the correlation with diffusion occurrence in the experiment performed. In the first 3 minutes (180 seconds) rapid increase in current flow is evident. At the 10 th second, amount of current is 1.20 ma. Already for 10 seconds, at the 20 th second, amount of current is 2.70 ma, which means increase for 1.50 ma. At the 40 th second there is already 4.80 ma, which is in time interval of 20 seconds increase for 2.10 ma. This is increase for 1.05 ma at the 10 th second in average. At the 60 th second there is 5.90 ma, which is in time interval of 20 seconds increase for 1.10 ma. This increase pace of 1 ma to 1.5 ma over 20 seconds goes on up to the 180 th second that is 3 minutes. Thereby, it can be noticed in that period is the greatest increase of 1.50 ma from the 10 th till the 20 th second. From 180 th second on diffusion is less and less intense (Figure 9). From the 180 th till the 400 th second, current flow increase is slight. This increase is of about 0.3 ma per minute. These slight increase indicates less and less diffusion of the salty solution. At the 360 th second diffusion is very little intense. From the 400 th (9.90 ma) till the 450 th (13.80 ma) we drill a hole in the membrane of the little container with salty solution (Figure 10). At the 450 th second we return the container into the water. During this period, a readout of 11

12 12 Passive diffusion current flow increase is 3.90 ma in 50 seconds. From the 400th till the 500th the greatest current flow increase is recorded. From the 450th (13.80 ma) till the 460th (17.30 ma) second current flow increase is 3.50 ma (in 10 seconds). In the period rapid current flow increase is evident as diffusion process speeds up. In order to speed up the diffusion process even more, mix the solution with a finger. From the 460th (17.30 ma) till the 480th (22.00 ma) second increase is for 4.70 ma (in 20 seconds), which is average increase for 2.35 ma in 10 seconds. At the 480th second, due to already sufficient current, the bulb begins to glow more weakly, that is to make less intense light (Figure 11). From the 480th (22.00 ma) till the 500th (30.60 ma) second we record the biggest increase for even 8.60 ma in 20 seconds, which is average increase for 4.30 ma for 10 seconds. At the 500th second, the bulb already glows stronger than when it began it glow (at the 480th second). Then, the remaining solution pour out of the little container and into the container with distilled water. This causes a small current increase in the next 25 seconds. In the last 25 seconds there is increase for 1.20 ma (from ma at the 500th second to ma at the 525th second). At the 525th second, with current of ma, the bulb glow is clearly visible although it is current of 50 ma needed for it to glow as much as possible (Figure 12). At this moment, the experiment is stopped as the diffusion process came to a stop. Figure 9. Amount of current of 8.30 ma at the 3rd minute; current flow increase decreases and diffusion becomes less and less intense

13 Passive diffusion 13 Figure 10. Amount of current of 11.5 ma at the 430th second; due to very little diffusion, we cut the membrane with scissors Figure 11. Amount of current of ma at the 483rd second; the bulb begins to glow slightly 13

14 14 Passive diffusion Figure 12. Amount of current of ma at the 525th second; the bulb glow is clearly visible; end of the experiment due to stop of diffusion occurring

15 Passive diffusion 15 Conclusion Based on the results gotten from the experiment, I conclude current was greater when there was more table salt (sodium chloride) going out from the little container through the membrane. This is diffusion of table salt which moved from solution with distilled water in the little container into the distilled water in the larger plastic container. Distilled water "travelled" when diffusing from the large into the little container, which is opposite from the direction of table salt diffusion. Diffusion of distilled water was not of such a great importance to us as sodium chloride diffusion was. I consider this experiment proved diffusion and thereby passive diffusion in living beings. In conclusion, passive diffusion is a very important process in life of an individual as it ensures matter exchange in organisms, such as for instance exchange of carbon dioxide and oxygen in lung breathing in human an animals as well as absorbing water in plants, and many other vitally important processes. 15

16 16 Passive diffusion References The Internet as a source of information and images df Expert work as a source of information Rusak, G., Katusic, A., Penic, S., Zivi svijet 1, biology students' book, pages , issue: 2009