Cell Communication Lab

Purpose

The purpose of this experiment, as the title suggests, was to study cell communication. Our subject was yeast and we tracked it's cell count over fourty eight hours. The controled variable in this experiment was time, where else the independent variable was percent of total cell count. As time passed on, we hoped to see whether the percent of total cell count would decrease or increase- mostly the latter. 

Introduction

Since yeast cells are incapable of moving, they communicate through signaling molecules. These signaling molecules, after being sent by one cell, are received by a G-protein coupled receptor in another cell. The pathway of the signaling molecule can be seen in the diagram below, supplied by Pearson Education. 

The cellular response in this case, is for the yeast cell to grow and divide. In our a and alpha culture of yeast, this will be seen as a budding haploid cell, where else the cells that have yet to receive the signal to grow will be single haploid cells. In our mixed culture, single and haploid cells will be present as well, along with schmoos, and asci. In a mixed culture of a and alpha yeast cells, the cells may recognize each other's presence and beging to grow towards each other- hence what we refer to as schmoos. Asci are bundles of cells growing next to each other, another aspect unique to mixed cultures.

Methods

In this lab, we put alpha-type, a-type, and mixed-type yeast in culture tubes filled with water.  We took samples of 5 drops of the yeast after 0 minutes, 30 minutes, 24 hours, and 48 hours and put them on viewing slides, then examined them with three different fields of view with compound microscopes on a medium 400x magnification. We counted the numbers of single haploid, budding haploid, shmoos, single zygote, budding zygote, and asci cells in each field, then calculated the percentages of each. 

Data Charts

Graph

DISCUSSION

 While observing our yeast through the microscope, no noticeable differences of alpha and a yeast could be seen. Even though they do have different genetic make up. The yeast that were on their own were mating at lower rates than the mixed yeast. In the mixed yeast, schmoos were visible sooner than the individual yeast. Yeast can communicate both indirectly and directly because if some yeast change, then they can send different signals out. When the yeast mate they can receive a signal directly from the opposite gender of yeast cells. Signal transduction pathways combine A and Alpha cells. When A and Alpha cells are together they are mixed. Mixed yeast cells can be haploid, zygotes, budding haploid, or even a shmoo.  When yeast cells mate, they use signal transduction pathways because G Protein receptors help them mate. 

 In our experiment the alpha yeast had more budding yeast cells than the A yeast cells. Our percent totals were approximately the same for alpha and A because they were leaning towards budding haploid cells more. In the mixed yeast cells, since there were A and Alpha, they reproduced sexually. On the other had the individual A and Alpha cells reproduced asexually. The Mixed Yeast cells started with schmoos then by the twenty four hour observation they were haploid cells. Then the haploid cells divided to form asci by the third day. According to our data, as the time went on, many more cells were produced due to reproduction. 

CONCLUSION 

     We are studying Cell Communication in this lab and we controlled the time when we observed the progress of the yeast cells. We observed cellular responses and the growth, then dividing of the yeast. Our percent totals of cell count increased as time when on. Cells communicate with receptors, especially G Protein Coupled Receptors, which aid in the reproduction process. Signal Transduction is also a method for the cells communicate. 

Plant Pigments and Photosynthesis Lab

PURPOSE

4A
The purpose of this experiment was to use chromatography to separate and identify the various pigments in chlorophyll.

4B
The purpose of this experiment was to determine the change in the rate of photosynthesis of chloroplasts when boiled or removed from light by using DPIP to determine the chloroplasts' electron output.

INTRODUCTIONS

4A Paper chromatography separates pigments by dissolving them in a solvent that moves up a strip of paper by capillary action. Different pigments are carried different distances by the solvent because of their varying solubility and attraction to the paper. Pigments like beta carotene that are more soluble and less attracted to the paper will be carried further than less soluble, more attractive pigments like xanthophyll. The distance traveled by the pigments is called Rf and is always the same for a certain pigment. It can be calculated as the quotient of the distance the pigment moved divided by the distant the solvent front moved. There are many light-harvesting pigments in chloroplasts. Chlorophyll a is the main photosynthetic pigment, absorbing blue-violet and red light best. Chlorophyll b and carotenoids are accessory pigments that are used to extend the plant's light absorption and to protect the chlorophyll a from too much harmful high-frequency light. 4B
Chloroplasts are found in plants and absorb light energy to "excite" electrons removed from water to produce ATP and NADPH, which are then used to fixate carbon into sugars in the Calvin cycle. However, the high-energy electrons produced that reduce NADP+ to NADPH can also reduce other electron acceptors, like the dye DPIP. DPIP is blue before reduction, but becomes colorless as it is reduced. DPIP, when blue, only transmits blue light, while colorless substances transmit all wavelengths of light on the visible spectrum, so as DPIP becomes colorless, it transmits more and more light. This transmittance can be measured using spectrophotometer.

METHODS

4A

Using a quarter to scratch off pigment off a spinach leave and placed that on a pencil line on the paper.  We took the chromotography paper and placed it into a cylinder with solvent. We waited time to see the pigments spread out over the paper. We mark where the bottom of the pigment band is. We measured the distance the pigment band moved. 

4B

In this experiment we set up a flood light, heat sink, and cuvettes. There were boiled and unboiled chloroplasts. We had five cuvettes the first was our control group. We put phosphate buffer and Distilled water to test tubes then DPIP to certain test tubes. We transferred the solutions to the correct cuvettes then added chloroplast to the cuvettes.  Immediately after adding the necessary chloroplasts we placed them behind the heat sink. We waited to place each in the colorimeter to read the rate of photosynthesis. Then tracked it on the logger pro. After taking them out of the colorimeter the cuvettes were placed behind the heat sink again.

GRAPHS

4A:

4B:

DISCUSSIONS

4A

From our trail, it appeared that the spinach sample separated into five different pigments. Due to the capillary action habits of plant pigments discussed in the introduction, we can guess that the top segment outlined in the corresponding picture above is beta carotene and the lowest segment is possibly xanthopyll. 

4B

To be completely honest, our experiment ended up being a complete flop due to incorrect usage of the colorimeter as can be even seen by our rather pointless data. However, I would like to ask the reader to focus on line 3 in Table 4.4 above. After realizing the mistake that had been made, we added a few more drops of DPIP into the cuvette containing the unboiled chlorophyl that was exposed to light. As can be seen from this set of data, the longer it was exposed to the light, the more transmittance was detected. This shows that over time, the DPIP was being used up in photosynthetic like reactions at a moderate rate. However, we don't have any other reliable data to compare it with but we can assume that transmittance in this cuvette was increasing at a faster rate than cuvette #2 yet slower than the boiled samples. 

CONCLUSION

4A 

From our trial, chlorophyll divided into five pigments.

4B

...I don't know what to say other than if time had been permitted we would have probably redone the experiment.