Thursday, December 19, 2013

Yeast Lab 12/19

Purpose: The purpose of this lab was to demonstrate cell communication through different stages of the mating of yeast.
INTRODUCTION: Cells communicate through the release of chemical signals which illicit varying responses in the unicellular colonies. In this lab there are 2 types of yeast (a) and (alpha) they each secrete a mating (a) and (alpha) factor respectively. When the (a) type yeast cell receives the (alpha) factor and the (alpha) type yeast cell receives the (a) factor a change in the cytoskeleton of each yeast cell type undergoes a change. Each cell cytoskeleton elongates because of the opposite cell factor binding to a receptor on its cell membrane that caused a specific signal transduction pathway. The cytoskeleton elongating forms a shmoo, each shmoo veers towards one another and finally meet to form xxa zygote.
Cells communicate in order to relay information and thus illicit a cellular response. One way cells communicate is through g-protein coupled receptors. A signal stimulates the receptor to undergo a transduction pathway. During this transduction period, the signal molecule activates the receptor to displace GDP to GTP. This causes the g protein to activate, thus relaying the information it got from the receptor to a neighboring inactive enzyme. The active protein activates the enzyme, thus evoking a cellular response.
Methods:  We obtained alpha, a, and alpha/a mix yeast with broth in three different test tubes.
We made 3 different wet mounts that contained the alpha, a, and alpha/a cultures on each slide. To avoid contamination, we used three different pipettes when creating the wet mounts.
We placed these wet mounts under a light microscope. The zoom was calibrated, as it was difficult to focus on the mass of yeast cells. First we looked at the cultures at a X10 magnification then under a X40 magnification.
Then we looked for fields in which the yeast cells were possible to count. We chose 3 fields per wet mount. We took readings at intervals of time 0, 30 minutes, 24 hours, and a final reading at 48 hours. We recorded the amount of haploid, shmoo, zygote, asci, and budding cells there were per field.

Discussion: We isolated the two different groups into a isolated and alpha isolated. The two isolated cells did not show much  communication. In the 24 hour period, there was a decrease of alpha and an increase of A cells, but at the 48 hour mark there was an increase of A cells and a decrease of alpha cells. It seems as though both cells had
opposite living conditions under which they survive the best. Also, the budding of both cells might have undergone some fluxes due to various concentrations in different parts of the wet mount we saw. For example, the presence of air bubbles in the wet mount. The air bubbles pushed away the cells, making them compact and harder to count.
The mixed group showed many stages of cellular communication. We saw haploids, shmoo, zygotes, spores, and ascus. This, unlike the isolated colonies, showed a much higher rate and greater sophistication of cellular  communication. The formation of all of these was due to the sexual reproduction between alpha type and a type yeast cells.
The most particular formation was the pear-shaped shmoo cell. It gets its pear shaped from its ability to recieve a ligand (signal) through a g-protein coupled receptor. (to see how a g-protein works, see the introduction). The formation of shmoos would be an example of local signaling as the cell changes shape from within. Because the yeast cells don’t have the motor skills to move, it grows to a potential mate. The g protein coupled receptor sends that signal and tells the cell’s nucleus to grow towards where the signaling molecule concentration is the highest. Thusly, the cell will have a bigger chance to mate. This explains the pear shape of the shmoo as it grows towards a potential mate.

As you can see here is the Alpha yeast. This is the isolated apha culture that was allowed to reproduce asexually. You can see the rise and the fall of both the haploid and the budding haploid population
Below you have the Alpha Yeasts and A yeasts as isolated cultures. You can see the rise and fall of both Haploids and budding haploids over the 4 periods of time.

Based on our findings, we concluded that yeast cells communicate via direct contact as well as pheromones. Since the yeast cell does not have the ability to move on its own, the easiest way it can mate is by fusing with a close, neighboring cell. Pheromones come into play when the cells are more spread out. Signaling molecules (ligands) are ejected from the cell, thus motivating the alpha/a cells to grow towards where the signals are of greatest concentration. This produces shmoos. Once in close proximity, mating and sporulation occurs. Proximity is an important factor as to where shmoos will appear first in a petri dish with both alpha and a type yeast. Since it will be most efficient to send a ligand over a shorter distance, shmoos will appear first in the area of least distance between alpha and a type yeast. In a hypothetical situation, if we are given a petri dish with 4 distinct regions marked in the petri dish and 3 of the circles contain alpha type yeast and one circle contains a type yeast, presence of schmoos will first be detected in the alpha circle closest to the a type circle.

Conclusion: We concluded that the most cellular communication happened when the a culture was mixed with the alpha culture. The zygotes, shmoos, haploid cells, and asci proved that communication between alpha and A yeast cells needs more signals to carry out more complex responses. On the other hand, we have the separated a and alpha cells which, on their own, did communicate but only formed haploids and budding haploids. This asexual reproduction allowed for the yeast to multiply though not as fast like the mixed cells.

References: Lab

Thursday, December 5, 2013

Chromatography and Photosynthesis/Light Reactions Lab (12/5)


Photosynthesis Lab
    The purpose of this lab was to test how boiled and unboiled chloroplasts and the presence of light affect the transmission and absorption of light in a solution of phosphate buffer, distilled water, DPIP, and chloroplasts.

Chromatography Lab
    The purpose of the paper chromatography lab was to calculate the Rf values of the different pigments in spinach. The purpose of this lab was to separate the different chlorophyll that exists in spinach leaves. This would separate the individual chlorophyll according to their size. Also, we used a color coder to reveal which specific chlorophyll we were actually seeing.


Photosynthesis Lab
    Set up an incubation area with a light, water flask and test tube rack, respectively. Keep the containers containing the unboiled and boiled chloroplasts solutions on ice. Label cuvettes 1,2,3,4,5, respectively. Cover cuvette 2 with tin foil. Label test tubes 1,2,3,4,5, respectively. Add 20 drops of phosphate buffer to all test tubes. Add 80 drops of H2O to test tube 1. Add 60 drops of H2O to test tubes 2,3 and 4. Add 63 drops f H2O to test tube 5. Now add 40 drops of DPIP to all test tubes with the exception of test tube 1. Transfer all solutions in the test tubes to their corresponding cuvettes, fill cuvettes 3/4 full. Now with respect to the spectrophotometer adjust the amplifier control knob until the meter reads 0% transmittence. Add 3 drops of unboiled chloroplasts to cuvette 1 and place it in the sample holder, adjust knob to read 100% transmittence by turning knob to the red light. You will now add a drop of unboiled chloroplast solution to cuvette 2, and immediately take a reading using spectrophotometer, removing tin foil to do so. After the reading place the cuvette in the test tube rack in the incubation area covering it with its tin foil. Let it sit for 5 minutes and then take another reading. Don't forget to recalibrate the spectrophotometer before every reading. You will take reading in intervals of 5 minutes up until 15 minutes. In respect to cuvette 3 also add a drop of unboiled chloroplasts. Cuvette 4 add a drop of boiled chloroplasts. Cuvette 5 will be used as is. Follow the same guidelines for readings and place cuvettes in incubation area in same intervals.

Setting up the individual cuvettes

Here is the device in which we placed the cuvettes in. It shone red light through the sample and then recorded it. 

This is our set up. Light is being separated via water and enters the samples. 

Chromatography Lab
    Obtain a long test tube. Add 1 cm of the provided solvent. Cut a piece of paper in a manner that it is long enough to reach the solvent but short enough to stopper the test tube. The paper will also be cut with a point, this end will touch the solvent. Draw a line 1.5 cm above the point. Place spinach leaf on top of pencil line. Rub the leaf with the edge of a coin. Repeat several times using a different part of the spinach leaf. Place the pigmented paper in the test tube now with the point barely touching the solvent and stopper the tube tightly. When solvent is 1 cm from the top mark the front. Remove the paper from the tube and mark the bottom of each pigment. Measure the distance the pigment migrated from the origin pigment line.

Extracting the pigments 

Isolating the paper with the pigment. Note the color. 

After about 10 minutes or so, there is already noticeable color separation of pigment. 

Measuring how far the pigment traveled. Cork was used to keep the paper from bending. 

Photosynthesis Lab
    The light in the flask will absorb most of the infrared radiation from the light and transmit most of the visible radiation. Wavelengths of light within the visible light spectrum power photosynthesis. Cuvette 2 will be covered with tin foil to prevent light from coming in it is a control group. The test tubes will provide room in which substances can become diluted. There is more H2O added to test tube 1 and 5 because test tube 1 will be used for calibration, and the extra H2O in test tube 5 replaces the chloroplasts. Cuvette 1 will be used to recalibrate between readings it demonstrates the measurement of a 0 and 100% transmittence, this is the scale on which the other cuvettes will be measured by. Recalibration between readings will reset the spectrophotometer.
Chromatography Lab
    In order to calculate the Rf values for the different pigments we observed, we used the equatiom for Rf values. Rf = (distance of pigment migration) / (distance solvent migrated). 


Photosynthesis Lab
    The phosphate buffer is used in the expirement in attempt to slow the light reactions, because in reality the reactions take place extremely fast. H2O in the experiment provides the electrons for the light reactions to take place in the chloroplast. DPIP is our form of NADP in the chloroplast which will be reduced by accepting electrons that are passed down the electron transport chain. So the light will hit the cuvettes and power photosynthesis. Each cuvette will contain chloroplast to a different degree. Depending on the contents of each cuvette and its conditions whether covered by tin foil or with boiled chloroplasts, different results will be obtained. In general H2O will donate electrons which through a series of steps including the passing through PS1, ETC, and PS2 in the chloroplasts; DPIP will be the last acceptor and there will be a change in color in the cuvettes from blue to colorless as DPIP is used. 
    As you can see in our graph the highest rate of absorption happened when the chloroplasts were unboiled and were exposed to light. This makes sense because the chloroplasts were not altered or boiled, and they were exposed to light which provided the partial fuel it needed to  carry out its reaction. 
    DPIP, as stated before, is an electron acceptor that takes place of NADPH. In our first attempt at this experiment, we used too much DPiP and not enough chloroplasts to yield good results. The fast acting DPiP already finished reacting with the chloroplasts, thus finishing the reaction by the time we got to our 2nd run. As a result, our data was unreliable past the second and sometimes third run.  In order to improve this, we decided to increase the amount of chloroplast while keeping the amount of DPiP the same. This would allow the reaction to go at a more gradual rate as DPiP has more chloroplasts to react with.  This made our data more gradual and reliable. We also calibrated our device in between every run to ensure that our data was as accurate as possible. 

Chromatography Lab
    For the paper chromatography lab, we were able to get 3 distinct bands of pigment. The first pigment we observed had an olive green color. An olive green colored pigment corresponds to chlorophyll b. The second pigment we were able to distinguish had a bright green color; bright green colored pigment indicates chlorophyll a. The last pigment we were able to see had a yellow color, indicating the pigment xanthophyll. It is worth noting that chlorophyll b and chlorophyll a were located closer to the marked line and did not travel that far up the filter paper. This is most likely due to the fact that the oxygen and nitrogen in chlorophyll make it cling to the paper more, preventing it from traveling farther up. Another interesting observation we made was that the xanthophyll pigment was located farther down the paper; the explanation we had for this phenomenon is that xanthophyll is not very soluble in the solvent we used.
    The solvent moves up the paper mimicked capillary action. This this is a result of the attraction of the solvent molecules to the paper (adhesion), and the attraction of the solvent molecules to one another (cohesion). As the solvent moves up it carries with it the pigments dissolved in it. The pigments travel different distances up the paper because they are soluble to the solvent unequally. Also each pigment attracts to the paper fibers differently. A pigment can bond to the paper fibers through H-bonds. In this manner certain pigments can near the solvent front more than other pigments when they are more soluble in the solvent and when they don't form H-bonds with the paper fiber. On the other hand other pigments will travel less and not near the solvent front when they aren't very soluble in the solvent and create strong H-bonds with the paper fiber.

Graphs & Charts:

Photosynthesis Lab

In this graph we have the rate of transmittence in percentage with the amount of time it took to transmit that amount. 
Run 1: Unboiled with light
Run 2: Unboiled chloroplasts with no light
Run 3: Boiled Chloroplasts with Light
Run 4: No chloroplast with light 

Here we have the absorption rate of the different runs. 

Run 1: Unboiled with light
Run 2: Unboiled chloroplasts with no light
Run 3: Boiled Chloroplasts with Light
Run 4: No chloroplast with light 

Chromatography Lab

Calculated Rf for each color that we saw. 


Photosynthesis Lab 
    In this lab we concluded that chloroplasts will react at the highest rate when they’re exposed to light and unboiled (not denatured). In contrast, the slower rate of light reactions occurred when the chloroplast is denatured and/or in the dar. That way the chloroplasts have no way of carrying out a light reaction. 

Chromatography Lab
    In this lab we found out the chlorophyll presence in the cells of a spinach plant. Using the chromatography paper, we concluded that the most prevailing cholorphylls were xanthophyll, cholorphyll a and chlorophyll b. In that order, from most present to least, the chlorophyll traveled up the chromatography paper separating the layers.


Monday, November 18, 2013

Germination and Cell Respiration Lab

Introduction: In this lab, we tested the effects of temperature as well as germination on the respiration of the barley seed. A plant is a living thing and needs energy to survive much like humans. When a plant undergoes cell respiration, it is using it's stored energy in the form of a sugar along with oxygen that's in the air to form water, CO2, and usable energy.
The equation is as follows: C6H12O6 + O6 → CO2 + H2O + Energy
As you can see, the hooded part is a 6 carbon sugar which is combined with oxygen yields carbon dioxide and water and usable energy.
That usable energy is then consumed by primary consumers which pass on a fraction of the primary energy it used to consume the plant out into the universe, creating entropy. When the barley seed is germinated, it means that it is ready to grow. The dormant stage of the seed is over and it begins to jettison extremities which require respiration. These extremities could be premature roots, leaves etc. So the question is, does the seed produce the most CO2 (respire the most) when it's non-germinated (dry and dormant), when the seed is germinated at room temperature, or when it's germinated and stored at a cold temperature.
Procedure: First we obtained the temperature of the room using a thermometer. Next we obtained 25 germinated barley seeds at room temperature and placed them in the respiration chamber. We placed the CO2 gas sensor in the chamber, sealed airtight. After a minute we started the CO2 gas sensor recording. After 10 minutes we stopped the recording and removed the CO2 gas sensor as well as the seeds. The seeds were placed in a beaker filled with ice cubes and water. The temperature of the ice water was recorded using a thermometer. We allowed soaking for 10 minutes. In the meantime we placed non germinated barley seeds in the respiration chamber following the same procedure to record CO2 gas emission. After 10 minutes we removed non germinated seeds and replaced them with the cold water germinated seeds that had been soaking. This was recorded for 10 minutes again using same procedure. Lastly we placed glass beads in the respiration chamber and recorded respiration.
Methods: By taking the temperature of the room we could determine the temperature at which the barley seeds were germinated. The CO2 gas sensor was sealed tightly to create a closed system and prevent gas exchange. By recording the CO2 gas in the respiration chamber we could determine the respiration of the room temperature germinated barley seeds. We placed the germinated barley seeds in cold water immediately after to allow time for the seeds to become as cold as possible. Recording the temperature of the cold water will help distinguish between cold germinated seeds and the warmer room temperature germinated seeds. Recording Non germinated barley seeds' respiration created a control group. Taking the respiration of the glass beads proved the validity of the respiration chamber using gas sensor.
Discussion: An immediate improvement that can be made to the experiment is letting the cold seeds rest in an ice bath while taking the CO2 reading. We could have let the container with the barley seeds along with the sensor sit in an ice bath. This would prevent the seeds from getting back into room temperature and would improve the reading of the cooled CO2.
This did not sway the graphs too off tilt and the data was similar across the board. Every groups graph showed a higher emission of CO2 in germinated seeds at room temperature, and lower CO2 emission in non germinated as wells as the cooled barley seeds. The trend makes sense because of the structure of the seeds. The germinating seeds need to make more energy to grow. Thus, they respire more and emit more CO2 than the dormant and and cooled barley seeds.
The rate of respiration was the highest in the pea seeds and the lowest in barley seeds. This is possible because of the chemical makeup and energy requirements for germination of the particular seeds.
Graphs & Data:

Room temp non germinated

Room Temp. Germined

Cooled Non germinated barley

Glass Beads (control for CO2 activity)

Class data

CO2 recording apparatus with dry barley

Germinated barley (note the extremities)

Glass beads for control group

Germinated seeds that yielded the most CO2

Conclusion: This lab proved that germinated barley seeds at room temperature release more CO2; therefore, they respire more than non-germinated seeds and germinated seeds at cold temperature. Even though the respiration rate of the cold germinated seeds and the room temp seeds was somewhat close, it is proven that barley seeds have an optimal temperature at which they respire the most. In this experiment, the seed respired less at a cold temperature, even less when it’s dry and dormant, and the most when its moist and at room temperature.  

Monday, November 4, 2013

Enzyme Lab 11/4/2013

In this lab we studied the effects of enzymes and their effect on various substances. An enzyme is a naturally occurring particle that speeds up a reaction. The enzyme takes in the reactants, adds a phosphor ion to the reactant, thus motivating it to do work with less activation energy. The overall release of free energy is the same even with the presence of the enzyme, which makes enzymes nifty. The substrate is the substance the enzyme acts upon. In this case, it was the yeast and the hydrogen peroxide. In this procedure, we tested for the concentration of hydrogen peroxide with an indicator KMO3.
Enzymes function at optimal temperatures and optimal pH levels. At an optimal temperature, the rate of the reaction is the highest. At optimal pH, the reaction rate is also the highest. In this experiment we conducted a test for optimal pH and see how the enzyme would react if we injected acid into the solution.
Also present in this experiment are catalysts. A catalyst is, in this case, a substance that affects the rate of the reaction. A catalyst can either inhibit or increase the reaction rate by lowering the activation energy. An enzyme is just a type of catalyst.
Baseline) First we added 10 mL of 1.5% hydrogen peroxide solution to a beaker. We then added 1 mL of water instead of enzyme solution. After we added 10 mL of sulfuric acid to stop the reaction. We removed a 5 mL sample of the solution into another beaker. We added Potassium permanganate to the solution drop by drop until solution remained a pinkish color.
Uncatalyzed hydrogen peroxide reaction) Here we placed about 15 mL of 1.5% hydrogen peroxide solution in a beaker. We let it sit overnight. The following day we added sulfuric acid to the solution. We took a 5 mL sample and added potassium permanganate drop by drop until a pinkish color remained.
Enzyme catalyzed hydrogen peroxide reaction) Here we placed 10 mL of 1.5% hydrogen peroxide solution in each of 6 beakers. We added an enzyme to each solution in this case yeast. We let each beaker sit for 10, 30, 60, 90, 120, 180, 360 seconds respectively. We added sulfuric acid after time was up for each beaker. Then we took a 5 mL sample from each beaker and added potassium permanganate drop by drop using a burette until the solution for each beaker remained pink.

Baseline) First we established a base line. Without adding catalase to the Hydrogen peroxide solution, instead water we could more easily determine the amount of hydrogen peroxide present at the beginning of the reaction. By adding the sulfuric acid it would stop any spontaneous reaction from proceeding. By taking  a sample and then adding potassium permanganate we can determine the amount of hydrogen peroxide present after the reaction has stopped. The amount of potassium permanganate added is proportional to the amount of hydrogen peroxide present. When the solution turns pinkish it represents a bit leftover of potassium permanganate that did not dissolve hydrogen peroxide.
Uncatalyzed hydrogen peroxide reaction) We left a solution of hydrogen peroxide overnight without adding a catalase to determine the rate of a spontaneous reaction. The conversion of hydrogen peroxide to water and oxygen. The next day we added sulfuric acid as it stops the reaction. We took a sample and added potassium permanganate to determine the amount of hydrogen peroxide that did not react or decompose into water and oxygen. This part showed the rate of an uncatalyzed hydrogen peroxide solution decomposition.
Enzyme catalyzed hydrogen peroxide reaction) The yeast added to each solution was the enzyme that will speed the reaction or decomposition of hydrogen peroxide to water and oxygen. And each beaker was left to proceed in its reaction for differing times before  sulfuric acid was added to stop the reaction. After we took samples of each of the differing time beakers and added potassium permanganate to determine the amount of hydrogen peroxide that was left. This part gave showed the amount of hydrogen peroxide left after being catalyzed by yeast at differing times in this case 10,30,60,90,120,180,360 seconds.
Some mistakes will be accounted for in this part of the lab. As you can see, our data does not correspond with the purpose of the lab. Our data table should have shown an inverse relationship between the time and the amount of KO4 we used in our experiment. This only happens from second 60 to 90 and then from second 180 to 360. The increasing amounts should have been higher than its preceding ml of KO4. We assumed that inaccurate samples were taken of the substances. For example, we might have taken a 10 ml sample rather than a 5 ml sample.
However, other groups have gotten the ideal inverse relationship of H2O2 decomposition with the time the enzyme got to react with the substrate. Ideally, the more the substrate got to interact with the enzyme, the less KO4 would be used to indicate the presence of H2O2.  This is true for our graph but only at the 360 second point. Everything else is a little off.    
The decomposition rate of the hydrogen peroxide is directly related with the enzyme activity. This is because enzymes speed up reactions by lowering the activation energy needed for the reactants to be converted to products. Although our data does not conform to the accepted trends, we know that the longer an enzyme is allowed to act on a substrate, more substrate will be catalyzed.  Since more substrate is catalyzed, it will take less indicator to find how much substrate is left.
Graphs and Data)

Our data
Our Graph


Acid/Enzyme denaturing

Yeast/enzyme test


Monday, October 21, 2013

Osmosis and Diffusion Lab (10/21/2013)



Part1A) For this lab we placed a solution of glucose and starch inside a dialysis tubing bag. We then placed this tube in a beaker containing water and potassium iodide. We wanted to determine whether or not the dialysis tubing bag was selectively permeable to the glucose and starch inside the tubing and the potassium iodide and water outside the bag.
Part1B) We wanted to determine the relationship between Molarity and percent change in mass for a dialysis tubing bag containing water and different concentrations of sucrose placed in a beaker of water.
Part1C) For this part of the lab, we wanted to determine the percent change in mass of potatoes when the potatoes were placed in a solutions of different sucrose concentrations. The reason we wanted to find the percent change in mass of potatoes is because we wanted to find the concentration of sucrose in the potatoes, and after finding the concentration of sucrose in the potatoes, we wanted to use this value to determine the solute potential of sucrose.
Part1E) We wanted to determine the osmosis taking place between an onion cell and a hypotonic, isotonic, and hypertonic solution in which the onion cell was placed. 




Part1A) In this part of the lab, we tested the selective permeability of the dialysis tubing. When an objects membrane is selectively permeable, it only allows certain nutrients to pass through. This is largely determined by the size of the pores as well as the size of the objects that are trying to pass through the membrane. 
Part1B) This next part of the lab tested for the ability of the dialysis bags to conduct osmosis. Osmosis is the passage of water through the selectively permeable membrane. The passage of water is crucial to all living things. However, too much water or too little water can be the differene between life and death. A human cell is isotonic. This means that there are equal amounts of water going in and out of the cell. The cell is in equilibrium and is functioning correctly. If a human cell receives too much water, it is in hypotonic state. The cell is bound to explode as the membrane cannot withstand the pressure exerted by the water. Conversely, the human cell can shrivel if too little water is present. In this situation, the cell is experiencing a hypertonic state where too little water is present to nourish it. 
In plant cells, the cell wall is strong enough to withstand a hypotonic stage ands actually prefers having too much water than too little. In the hypotonic stage, the central vacuole is highly bloated and the plant stands upright. In the isotonic stage, the plant begins to wilt and droop as the cells do not have enough to hold them upright. In the hypertonic stage, the plant cells do not have enough water to sustain life and dry out and die. 
Part1C) In this part of the lab, we tested the water potential in the potato cores by means of calculation. Water potential is waters tendency to move from a lower concentration of solute to a higher concentration of solute. The two factors that effect water potential is the sum of solute potential and pressure potential. So, there is a direct relationship between pressure potential and water potential. As water rushes into a cell, the pressure on the inside rises as well as on the outside in order to keep the cell from bursting. As pressure rises, the more water potential outside the cell.  Solute potential is a little more ambiguous. Solute potential is always negative. Water travels towards higher concentration to evenly disperse the solution. Since there is less water in the solute, this decreases the water potential. 
Part1E) In this part of the lab we looked at images of an onion cell in an isotonic, hypotonic and hypertonic solutions. Respectively, when a cell has equal amounts of water going in and out, too much water going in, and too little water. We looked at traces of plasmolysis. Plasmolysis is the shriveling and eventual death of a cell due to lack of water. 

Class Data:




All solutions inside bag with increasing molarity soaked in water


Part 1E)


Part1A)  We had to first create a dialysis bag by tieing off one end of dialysis tubing. In order to test what substances could or could not pass through the membrane of the dialysis bag, we had to first fill the dialysis bag with a solution of 15mL of 15% glucose and 1% starch. After filling the bag with the glucose and starch, we tied off the other end of the bag.  We then obtained a 250mL beaker, and we filled the beaker with a solution of 250 mL water and 4mL of potassium iodide. In order to create a scenario of diffusion between the contents in the dialysis bag and the solution in the beaker, we had to place the dialysis bag in the beaker. After allowing the bag to remain in the environment of the water and potassium iodide solution for 30 minutes, we used a glucose indicator to test the solution inside and outside the bag for glucose. 
Part1B) For this we had 6 dialysis bags and 6 beakers labeled: distiller water, .2M,.4M,.6M,.8M, and 1.0M for the different concentrations of sucrose. We followed the same method for making a dialysis bag out of dialysis tubing; filling each bag with a different concentration of sucrose, we made sure to leave enough room for the expansion of contents inside the bag when we tied the second end of the dialysis tubing. We filled the 250 mL beakers 2/3 filled with distilled water. Before placing each bag of sucrose solution into the corresponding beakers of distilled water, we took the mass of each bag using a gram scale. After allowing the bags to be submerged in their corresponding beakers for 30 minutes, we removed them and retook the bags' mass.
Part1C) First we placed differing concentrations of sucrose solution approximately 100mL in beakers. Next we took a potatoe and used a potatoe cork bearer to cut 24 cylindrical potatoe cores. We took the mass of 4 cores and placed them in a beaker. 4 cores per beaker. We covered the beakers with plastic wrapping after all cores were placed in their corresponding beakers to prevent evaporation. We let the beakers sit overnight and then we took the cores out and patted the cores with a paper towel to remove any water on the outside before placing them on the scale. The mass was retaken.

Part1E) Here we looked at images of onion cells that were soaked in isotonic, hypotonic and hypertonic solutions. We looked for the difference in structure as well as the appearance of the cell in the three different stages. We then analyzed the different pictures of the onion cell and the distinct attributes that go with the different stages. 
Part1A) In this part of the lab we tested for the dialysis bags selective permeability. Our results showed that the dialysis bag is permeable to water, iodine, and glucose but not starch. Along with every other group, the contents (15% glucose 1%starch) were dyed blue to and the outside remained a yellow/orange. The blue indicated the presence of starch and the later test for glucose with the strips which was present in both inside and outside the bag. Every group concluded that the dialysis bag was semi permeable. It allowed starch, glucose and water to pass through while leaving starch in the bag. All groups agreed to these facts and test results. It was consistent with every group. This was the cleanest test of the entire class far as consistent data collection. 
Even though the data for every group was the same, this lab could be improved. In order to ensure consistency, ever group should have the same amount of iodine, solution, and water. This would ensure consistent data collection. 

Part1B) This part of the experiment tested the permeability of the dialysis bag as well as its ability to diffuse water. Our data relatively matches the class data with a few exceptions. The trend is relatively the same. As the molarity increases, so does the percent change in mass. The only difference in our data and the class average is that while the other groups averaged about the same (around the 10 range) our percent change was in the 25+ range. We believe this is caused by the amount of sucrose solution we put inside the dialysis bags in relation to other groups. We put in a lot more sucrose solution inside the bag which allowed more water to diffuse into the bag, increasing its mass. This could account for our changes in mass to be way higher than that of the class. However, our data still confirmed the trend as molarity increases, more water will diffuse across the bag to even out the molarity of both sides of the membrane. This experiment supports this trend. 
Only change to this lab that would improve it is to have some form of measuring the amount of sucrose (i.e beaker) so the amount is the same for every bag. Then we can more accurately see the trend while maintaining data that doesn't range too far from group to group. 

Part1C) Our data in this portion strayed lower than the class average yet there was an observable and consistent trend. There is an inverse relationship between the percent mass of the potato cores before and after the soak and the molarity of the substance. As molarity increased the % mass of the potato core decreased. The rest of the groups experienced the same trend. By the time the potato was soaked in the 1.0 M sucrose solution, there was a 22% decrease in mass on average. The data did eventually level out at the end. This wold account for the pressure potential. The class and our group saw this trend. The results support the fact that the higher the solute potential outside the potato, the more water potential there will be inside the cell which results in a loss if water and overall mass. 
In order to improve this experiment, the amount, size and shape of the potato cores should have been the same for all tests. This would have resulted in more consistent and accurate data that would not range too far from group to group. 

Part1E) This experiment was based off of the images we have in our reference below and our data/graphs section above. In this experiment we looked at images of the behavior of an onion cell when soaked in an isotonic, hypotonic, hypertonic solutions. We looked for evidence of plasmolysis. We found it in the picture of the hypertonic solution. The cell appears shriveled and less functional than the cell in the hypotonic solution. 
These observations were consistent with every group, as images on the Internet of a lab aren't too hard to find and compare to data stated in the lab. 
Part1A) Our results showed that the dialysis bag formed a selectively permeable membrane that did not allow starch to diffuse out of the bag. We were able to see that the bag did allow glucose and potassium iodide to diffuse across its selectively permeable membrane through a glucose test and our observations. We took an initial glucose of the beaker full of water and potassium iodide, and the test affirmed that there was no glucose present in the beaker; however, after placing the dialysis bag full of glucose and starch in the beaker and allowing time for diffusion, glucose did indeed diffuse out of the dialysis bad. Our glucose test affirmed that there was glucose present in the beaker. Using our oberserations, we deducted that the potassium iodide did diffuse into the bag, for the colorless nature of the bag changed to blue. Osmosis of water cannot account for the change in the color of the bag, so potassium iodide must have diffused into the bag since the combination of starch and potassium iodide yields a blue color. Through this knowledge of knowing that a mixture of starch and potassium iodide will be indicated by a blue color, we were able to deduce that starch did not diffuse out of the bag because the color of the solution outside of the bag but I'm the beaker remained yellow, the initial color of the potassium iodide and water solution.

Part1B) After placing dialysis bags full of different concentrations of sucrose ranging from .2M - 1M and using a control group of distilled water, we were able to see changes in the mass of the dialysis bags. Since the beakers were full of solely water and the dialysis bags had differing concentrations of sucrose, we essentially were able to create a hypotonic solution. There was more sucrose in the bag than outside the bag. Our results showed that the higher the Molarity of sucrose in the dialysis bags the increase in mass after removed from the beaker of water was greater. Compared to the control group the other dialysis bags with differing concentrations of sucrose absorbed more and more water as the Molarity of sucrose increased. This demonstrates that the in order to balance out a higher molarity of sucrose in the bag more water diffused into the bag. There's  a clear direct relationship between the molarity of the sucrose in each dialysis bag to the percent change in mass after it was removed.

Part1C) After soaking the potato cores in different sugar solutions, we noticed a change in the initial and final weight of the potato cores. This change is due to the molarity of the solutions the potato was soaked in. The higher the molarity, the lower the percent change of mass tended to be. The potato cores lost the most weight in the over night soak in the solutions with the higher molarity. This test of water potential is proven through this change in weight. As the potato cores sat in different sucrose concentrations, the potato increased water potential as the molarity rose. This shows an inverse relationship with molarity and the water in the potato. 
Part1E) This part of the lab was conducted from various pictures online (shown in the graphs and data portion of our lab) and it was to prove that solutions of different concentrations around an onion cell cause the onion cell to undergo plasmolysis. This lab proved that the higher the concentrations of solute around the cell, the more water wants to leave the cell. Thus, the cell membrane contracts and shrinks as water diffuses across the membrane. The more water that diffuses out of the cell, the more the membrane shrinks and contracts.