Cell Communication Lab

 

Purpose:

The purpose of this experiment is to examine the reproduction of yeast cells and how cellular communication plays into it.

 

Intro:

Cellular communication occurs via chemical signals that coordinate functions and respond to stimuli. Chemical signals can come from the environment, other cells in the same organism, or other organisms. Cells can communicate by direct contact, local signaling, or long distance signaling. Yeasts are unicellular fungi that can reproduce sexually or asexually. They alternate between haploid and diploid phases. During asexual reproduction, single haploid cells turn into budding haploid cells, which creates a new daughter cell. During sexual reproduction, in response to a specific chemical signal, haploids can change from an asexually reproducing cell to a gamete. There are two sexes: a-type and alpha-type. When these types mix, they grow towards each other, forming shmoos. The shmoos then fuse to create a zygote, which divides to form new yeast cells. 

 

Methods:

After placing the yeast solution (alpha type, a type and mixed) into seperate test tubes we measured using the light microscope; to find the starting amount of yeast cells. Then took measurements at different increments of time (30 minutes, 24 hours and 48 hours) to see what percent increase the yeast colony experienced periodically.

 

 

                                                      

                                                                   Mixed at 30 minutes

                                                    

 

                                                  

                                                                       Mixed at 48 hours

 

Data: 

 

 

                                                           Data for A and alpha yeast

 

 

                                                                Data for mixed yeast

Graphs:  

 

 

 

 

                                     

 

 

Discussion: 

In this lab we tested the reproduction patterns of alpha type and a type cells.  We also tested a solution of mixed alpha and a type yeast.  What we saw was this:

Alpha type yeast: Over time, the percentage of single haploid cells decreased.  At 0 minutes 77% of the cells were single haploid cells.  At 30 minutes, 76%, and at 24 hours, about 22%.  This can be attributed to the fact that there would be more formation of budding haploid cells due to the progression of time, so single haploid cell percentage would decrease.  But, we saw an increase after 48 hours, where the percentage hit 85%.  There was such a large increase I yeast concentration that the percentage of single haploid cells must have gone up.  After a certain amount of time, there must be a pattern where single haploid cells will produce budding haploid cells, and this is what happened here.  For the budding haploid cells, we saw a rapid increase.  Starting at about 23%, it increased to 24% and 77% during 30 minutes and 24 hours respectively.  But, we also saw a decrease in percentage at the 48 hour mark (14%).  

 

A type yeast: We experienced much of the same trends for the a type yeast.  Over time, single haploid cells decreased at first them increased rapidly.  It started at 89%, at 30 minutes it was at 40%, and at 24 hours it was a 15%.  But, at the 48 hour mark, it increased rapidly (85%).  For budding haploid cells, it started at 10%, increased to 60%, increased again to 84%, then decreased to 14%.  The data we had was very similar for both a and alpha type yeast, leading us to believe that they reproduce in much of the same way.

 

Mixed yeast: This sample was a combination of the a type and aha type yeast cells.  For the single haploid cells, we saw a steady decrease.  It started at a little less than 50% of the total cell count, and ended at about 29%.  This is because single haploid cells will become budding cells and eventually form asci over time, so the cell count will continually decrease.  For budding haploid cells, we observed an overall decrease as well, starting with about 17%, it gradually decreased to 7.4%.  This too, can be attributed to the fact that cells will start to form asci over time, therefore decreasing the number of free floating cells.  For the shmoos, we saw a maximum percentage of 21.8% at 30 minutes.  It then decreased to close its original percentage at 24 hours, but then increased to 17.7% at 48 hours.  For the single zygotes, we saw 7.6% at the 0 minutes. Then we saw 5.9%, 19.5%, and 11%.  For budding zygotes, the data varied by increasing, describing, and increasing once more.  The most important sample from this experiment was the percentage of asci.  It started at a relatively low percentage of 6.4%.  It ended up being at 27.4%.  This is important because as time goes by, yeast are able to communicate as a whole.  When time passes, more yeast communicate with each other,  so they are able to come in close proximity to eachother, and form asci.  

 

Basically, for a and alpha type, when time progresses, we see the overall number of yeast cells increase.  We can see that yeast has the ability to reproduce because of the increase in budding haploid cells, and therefore an increase in overall cell count (yeast cell count must increase because it is reproducing).  For the mixed type, we see an increase in the percentage of asci, which means that there was an an increase in cell communication due to the lapse of time.  Overall, the cells that denote the reproduction of yeast increase over time.  We know that yeast can't physically move because, at zero minutes, it would all conglomerate together.  Rather, it communicates by means of chemical signals.

Conclusion:

From this lab we can conclude that over time the yeast concentration increases. It is able to do so because it communicates bby means of chemical signals called pheromones. When time passes the concentration of yeast increases showing thaat it is able reproduce through chemicall signals. 

 

 

 

 

 

Plant Pigments & Photosynthesis Lab

Plant Pigments Lab

Purpose: 

The purpose of this experiment is to identify the pigmengs in chlorphyll and test how fast the pigments move up the chromatography paper.  This helps establish Rf values. 

Intro: 

Paper chromatography is used to seperate and identify pigments in cell extracts. The solvent moves up the paper because of the attraction of solvent molecules to the paper and the attraction of solvent molecules to each other. The solvent carries the pigment up the paper with it, but the pigments move up at different rates depending on how soluble they are and how much they are attracte to the paper.  Pigments in plants are used to trap light energy in order to perform photosynthesis.  The photons in light excite the electrons created from the splitting of water, and because pigments are able to harness that energy from photons, photosynthesis is able to be carried out. 

Methods:

First, we obtained a 50ml graduated calendar that contained 1cm of solvent in it.  Then, we cut a strip of filter paper and cut a point onto the end.  Next, we drew a line 1.5 cm above the tip of the point and placed a small leaf on it.  We then crushed the leaf onto the filter paper with a coin.  Next, we put the filter paper in the solvent. Once the solvent was within 1 cm of the top of the filter paper, we removed the paper and marked where each line stopped (both the pigment and solvent line).  We then measured the distance between the original and current line.  We repeated these steps for several other pigments as well.  The pigments used were Beta Carotene, Xanthophyll, Chlorophyll A, and Chlorophyll B.

Data/Graphs and Charts: 

Discussion: 

In This lab we used Chromatography paper to test the solublity of the different pigments found in spinach leaves. By placing the chromatography paper into the solvent the pigments where drawn upwards by Capillary action. Through Capillary action the solvent molecules stick to the paper and to each other. Which is quite similar to cohesion and adhesion of water molecules! When then the process was complete the solvent had left behind particles of the different pigments that were in the spinach leaf. We had 5 different lines of pigments that spread across the paper from top to bottom. From the point where we placed the spinach leaf molecules on to the paper was about 20 mm from the tip of the paper, the color of the pigment was a dark yellow color meaning that this is most likely Chorophyll B. Then the next strip of left over pigment molecules was at 40 mm and green in color. This is the band of Chlorophyll A molecules. the chlorophyll molecules are closer to the orginial pigment molecules of spinach because they are bound closer to the paper than the other pigments. The next band of pigment was at 52 mm and was yellow-green in color.This is one of the non-major pigments that are not listed in the lab or this could mean that there was a slight error in our lab. The next was Xanthophyll which is recored at 80 mm from the bottom of the paper and is a pale yellow color. Xanthophyll is higher up the paper because it is more soluble than the chlorophyll pigments, but less soluble than the Beta Caroten, since it contain oxygen and is slowed by forming hydrogen bonds with cellulose. At the top we have Beta Caroten (a yellow-orange color), it is the highest because it is very soluble  and is not slowed by the formation of hydrogen bond with cellulose, moving it up the paper the highest. For the relationship that is shown between the distance the pigment migrated from the front and from the distance solvent front migrated we had: Beta Carotene- 2.142, Xanthophyll- 1.124, Cholorophyll A- 0.571 and Chlorophyll B- 0.286. This data shows that Beta Carotene traveled the furthest from the original band of pigment where the spinach molecules were placed and supports our findings from the experiments. 

Conclusion: We concluded that Beta-Carotene moved the farthest up the chromatography sheet.  The Rf factor for Beta-Carotene was 1.  The pigment that moved the least was Chlorophyll-B.  Its Rf factor was .286.

Photosynthesis Lab 

Purpose: 

This experiment tests the hypothesis that light and chloroplasts are needed in light reactions. DPIP will take the place of NADP, which will be reduced. This will cause the DPIP to turn from blue to colorless. Based on the measurements of light transmittance, we will be able to tell which solutions have the highest rate of photosynthesis.

Intro: 

During photosynthesis, light is absorbed by leaf pigments and the electrons gain energy. Then, NADP is reduced to NADPH. ATP and NADPH are then used in carbon fixation, which turns CO2 into organic molecules.  Photosynthesis needs several things in order to be carried out.  The first thing is the presence of light.  Light excites the electrons that exist from the splitting of water, and those electrons are then able to make their way down the electron transport chain.  Another thing that is necessary for photosynthesis to occur is water.  Water is the source of electrons that help create the difference in proton gradient, which then causes ATP to be created.  Also, a plant must have a pigment that has the ability to absorb light.  The main pigment is chlorophyll-a, but many other photoreceptive pigments exist.  Carotene and chloraphyll-b are examples of other pigments.  The last thing that is needed for photosynthesis is active proteins.  Proteins make up the electron transport chain found in photosystem I and photosystem II, and there are also proteins used in carbon fixation during the Calvin cycle.  

Methods:

Day 1

 First, we prepped five different cuvettes with different solutions.  In the first cuvette, we put only the phosphate buffer, water, and chloroplasts.  In the second cuvette, we put DPIP, water, and unboiled chloroplasts, and phosphate buffer, but we placed a layer of tinfoild around it to mimic a dark environment.  In the third cuvette, we put inDPIP, water, and unboiled chloroplasts, and phosphate buffer.  In the fourth cuvette, we put in DPIP, water, and boiled chloroplasts, and phosphate buffer.  In the fifth cuvette, we put DPIP, water, phosphate buffer, but no chloroplasts.  The chloroplasts weren't put into the solution until they were ready to be put under the light.  Next, we calibrated the colorimeter with the blank cuvette (the one containing only DPIP and water) in order to establish what 0% transmittance was.  Next  we measured the reast of the cuvette in the colorimeter.  We then put the cuvette behind the lamp (with the heat recepticle between the lamp and the cuvettes), and kept time for five minutes.  Once that was complete, we placed each cuvette in the colorimeter to measure the % transmittance.  We repeated these steps for time increments of 5, 10, and 15 minutes as well.  Listed below is the contents of the solutions for each cuvette.

        

        

Day 2
We used the same methods for day 1, but instead we put 2 drops of DPIP in.

Data:

                                                                             Day 1

Day 2

Graphs and Charts:

Discussion:                

Day 1

In this experiment we were testing how chloroplasts and lights are essential for light reactions to take place. We also substituted NADP for DPIP, which is another electron acceptor. When the light hits the chloroplasts the electron levels are raised and will reduce the DPIP. This will cause the chloroplasts to change from blue to colorless, this proves that chloroplasts and light are needed because when the solution changes to colorless that means that the electron acceptors are being used by the electrons brought into the solution by light. Our control would be Sample 1, which was the blank that had no DPIP added but had the unboiled chloroplasts. In this sample we had add amount of transmittance , there was a reaction that was near 100% transmittance. Since this is the cuvette we used to calibrate the spectrometer. The second smaple was the unboiled chloroplasts without light and DPIP, with this there should be no reaction so the solution stayed blue. We placed the foil over the cuvette to block the light which stimulates the reaction. Since we had a low amount of transmittance ( about 98.5% at the end of day 1 and 71% on day 2).  This indicates that human error did occur.  The third sample of unboiled chloroplasts with light had a amount of tranmittance, this is the sample where all the necessary components are available for photosynthesis to function properly (Light, Unboiled chloroplasts & DPIP) then the solution changed to colorless. Sample 4 had boiled chloroplasts with light and DPIP, and at the end of day 1, the percent transmittance was at 94.81, and at the end of day 2, it was 66.49%. Because the chloroplasts weren't able to function due to the denaturing of the proteins involved in photosynthesis, this percentage was lower compared to the rest of the samples. The last sample 5 has no chloroplasts what so ever, meaning that there can't be a reaction because without chloroplasts the percent transmittance was nonexistant on behalf of light having to strike the chloroplasts for this reaction to take place. The research we obatined from this experiment does for sure prove that you need chloroplasts, an electron acceptor and light. 

Day 2

On day two our challenge was to somehow slow the reaction, so that our percent transmittance wasn't so high.  It jumped about 88% to about 98% percent, so tracking the increase in transmittance was more difficult.  We decided in our lab group to increase the DPIP concentration by 1 mL. By doing this we found that the change in transmittance was less drastic in the 15 minutes of testing period. This successfully translates to  slowing the reaction rate. Since we increased the electron acceptor concentration the reaction couldn't go out of control since the electron acceptors are what play a major role in controlling the reaction rate. 

Conclusion: 

Both the dark and light cuvettes (cuvettes 2 and 3) experienced the highest rate of transmittance.  Cuvette 2 had a final transmittance reading of 98.89 on day one, and 71.16 on day two. Cuvette 3 had a final transmittance reading of 98.05 on day one, and 69.70 on day two.  Although cuvette 2 did have a high transmittance rate, it was most likely caused by human error.  The rate of photosynthesis occurs slower in the dark, and eventually doesn't occur at all, so cuvette 2 must have been exposed to light accidentally.  Therefore, chloroplasts that haven't been denatured by boiling and are exposed to light will have the highest rate of photosynthesis.