Yeast Lab

Purpose: The purpose is to demonstrate the contrast between the reproduction of a culture if yeast if all one type and one of a mixture. We are going to observe how much reproduction occurs in a sample of all a type, all alpha type, and a sample of a group with mixed typing. 

Introduction:

Cells communicate by sending and receiving signals that come from other places such as the environment or even other cells. To trigger these responses the signals have to cross the membrane by either crossing itself or using receptor proteins that are in the surface. Yeast are unicellular fungi. Not much is needed for them to survive except for reduced carbon, nitrogen, biotin and salts and trace elements. Yeast is anaerobic and go through alcoholic fermentation. They also reproduce both asexually and sexually. When they reproduce sexually they need an alpha and an "a type" yeast cell. They then will grow towards each other once they receive each others fermone. They then will turn into a zygote and eventually reproduce. In our mixed culture of A and Alpha type you will observe:

Shmoo:

Zygotes:

                                                                           Budding

                                                               Third Image is a single Zygote

Single and Budding Haploids:

                                                       Pink is Single and Blue is Budding

Asci:

Methods: In this lab, a-type and alpha-type yeast cells were used. Using three test tubes, one containing a-type, 2 ml of water, and liquid agar, then two more were made using alpha-type yeast and a mixture of the two. Each culture was observed under a microscope at different time intervals, and the haploids and budding haploids were counted for the solutions containing one type. For he mixed type, haploids, zygotes, and asci were counted. The cells were counted at intervals of thirty minutes, twenty four hours and forty eight hours. The various types of cells were observed, counted, and documented in three different fields of view per culture. 

 Data:

Graphs and Charts:

Discussion:

In our lab, we focused on two types of yeast. A type and alpha type. There were few differences seen between the two types, however, I noticed that the A type seemed to produce asexually a lot more than the alpha type did. Looking at our data this is also supported. Other than the sheer amount of the haploids we could see, very little else is different.

                                                         A Type Yeast at 48 Hours

                                                          Alpha Type Yeast at 48 Hours

 However, when we look at the mixed culture and our two separate cultures, we notice plenty of different things.

Mixed Culture at 48 hours

         Things formed in the mixed culture that we didn't see in the two isolated cultures. We observed not only single and budding haploid cells as we did in the isolated cultures, but we also saw shmoos, single and budding zygotes, and asci. These different things were the result of the mating occurring between the two types. As the time went on the yeast mated more and more producing more yeast molecules as can be seen in our data. They find each other by releasing pheromones that act as a signaling molecule in a G coupled protein receptor. This signal molecule allows the G coupled protein receptor to activate and produce the cellular response of growing towards each other and then mating. Since the two types of mating are very visually different it would be easy to conduct an experiment to determine which type was which if given a blank plate with no label. You could make two samples and add A type to one and Alpha type to another and which ever begins to form the different things such as shmoos, single zygotes etc. then you would know whether it was alpha or A. 

Conclusion:

The yeasts in the mixture had a lot of single haploids instead of having more asci. Even after 48 hours there wasn't that many asci. There was no set ratio that went on in the mixture. But there seemed to alway be more single haploids than anything. There weren't that many shmoos and budding zygotes. What we conclude is that when we looked at the yeast they had already gone through those phases. There were more single zygotes though. There was a difference between the alpha and a type yeast cells. A type produced asexually more than alpha did. Though at each observation we observed vastly more cells, the relative concentrations of each type of cell remained relatively constant.  

References 

http://learn.genetics.utah.edu/content/begin/cells/insidestory/

Also the lab background 

Plant Pigments and Photosynthesis

Lab 1

Purpose: The purpose of this lab was to be able to see the many different pigments that make up the leaves colors. This would provide us with an explanation of why the leaves change colors in the fall. 

Introduction: Chromatography is used to separate the pigments of the leave. The paper allows the different pigments to grab onto the paper and begin to spread at different speeds causing them to separate. This allows us to observe which pigment moved up the farthest and also to see all the pigments that go into the color of a leaf. 

Methods: For this experiment, we put 1 cm of solvent in the bottom of a graduated cylinder. We then took a piece of filter paper, cut it to a point, and used a coin to rub some of a spinach leaf onto the paper. We then submerged the tip of the filter paper in the solvent, allowing it to move up the paper and carry the pigment with it. When it was near the top, the filter paper was removed and the location of each band of pigment was marked.

Data:

Distance from the solvent line.

The paper used and next to a ruler

Discussion: The first time we did this expirement we didn't add enough pigment, so the lines were not visible. The second time we did and the pigments went up the paper. Chlorophyll B was the one that went up the lowest with 33 millimeters from the point. Xanthophyll was next with 43 millimeters from the point. Chlorophyll A was the third from the point which was 72 millimeters. The fourth was beta carotene with 129 millimeters. We could have added more pigment for better results and brighter more defined lines.

Conclusion: This lab demonstrated that there are many pigments involved in gathering energy from the sun. The different locations on of these pigments on the filter paper demonstrated the varying amount of these pigments, as well as the relative solubility of each. 

References:      http://www.howstuffworks.com/chromatography-info.htm 

Lab 2:

Purpose: The purpose of this lab was to see the effects of DPIP, boiled or unboiled, and amount of light on the percent transmittance using a spectrophotometer. Our control group was cuvette one because it contained no DPIP, unboiled chloroplasts and was exposed to light. The other 4 were our experimental groups. 

Introduction: Spectrophotometers are used to measure the percent of transmittance from a solution placed in the machine. Transmittance is the amount of light that makes it through the solution. Absorption is how much of the light is absorbed by the solution.  Spectrophotometers use a light source that is shined through the solution and on the other side is a sensor that measures how much is transmitted through the solution and how much is absorbed.

Methods: We first added distiller water to a phosphate buffer, this was in all of the test tubes for all five solutions. Then we added DPIP and boiled or unboiled chloroplast to the test tubes. Then we filled the cuvettes three quarters of the way full and put it in the colorimeter. We put the cuvettes behind a light for five, ten and fifteen minutes. We took the readings of how much light was transmitted through.

The amount of each item we needed to put in each test tube.

The lest up we used for to have light in the cuvettes.

Data:

Graphs and Charts: 

Discussion: Only the graph of our 2nd attempt is pictured above. In our first attempt, we got very strange and inconsistent data, but using double the DPIP for our 2nd attempt corrected the problem.  Looking at our graph, it can easily be observed that cuvettes 3 had the highest transmission. This is almost certainly because it most closely mimicked natural photosynthetic conditions. The chloroplasts were unboiled and therefore not  denatured, and there was light shining on it. This allowed the electrons in photosystems I and II to be excited, beginning photosynthesis and eventually processing DPIP, turning the solution from blue to clear and allowing for a higher transmittance. On the other hand, all the other cuvettes showed a much lower transmittance rate, because in each case the chloroplasts were either boiled, starved of light, or both, preventing photosynthesis from starting and therefore causing DPIP to remain unprocessed and the solution to remain blue. 

Conclusion: The lab shows that transmition of light through the solution is best in conditions that are like the natural conditions of  a plant. DPIP is processed when there is light and unboiled choloroplast. Light and non denatured chloroplasts are essentual for photosynthesis to occur, so seeing that the solution that was most like natural photosynthetic conditions had the most light transmittance, meaning it was most effective at photosynthesis. 

References:

Lab 4 Plant Pigments and Photosynthesis

 http://simple.wikipedia.org/wiki/Spectrophotometer

http://www.biologyjunction.com/lab_4_plant_pigments.htm