Cell Communication Lab

Purpose

The purpose of this lab was to investigate cell signaling between two strains of yeast- a-type and alpha-type. We observed the mating interactions between the two. 

Introduction

Cell-to-cell communication, or cell signaling is an important function of cells. It occurs within multicellular organisms and between unicellular organisms. Cells can communicate with each other a few different ways, although the most popular way is via chemical signals. Yeast, also known to the science world as Saccharmoyces cerevisiae, has two mating types as mentioned earlier. The two different types communicate with each other through signal transduction pathways via secreted factors. A signal transduction pathway is a series of steps in which a message received at the cells surface is amplified through transduction which then triggers a response. In yeast cells, a-type cells have receptors that receive chemical signals from alpha-type cells. Alpha-type cells also have receptors that receive chemical signals from a-type cells. That way, when they secrete their own chemical factor, the opposite type is able to receive it. Once the two yeast cells receive the signaling factor from the other type, they begin to change their cytoskeleton in order to "grow" toward their mate. This elongation of the cell is called a shmoo. 

Yeasts can reproduce sexually and asexually. In asexual reproduction, also known as cell division, both the a-type cells and alpha-type cells bud in order to produce daughter cells, or haploids. In yeast, the haploid cell can turn from an asexually reproducing cell to a gamete, or sex cell. The yeasts then stop dividing and grow into their gamete shmoo form. the yeast begin to grow toward their partner and fuse together. When the two types come together, they form a diploid zygote. 

We used a toothpick to pick up a colony of each type of subcultures of yeast and put them into their designated culture tube filled with 2mL of sterile water.

We used a transfer pipet to transfer 5 drops of yeast suspensions onto their designated plates.

Data:

Discussion
In this lab, cell communication among yeast cells were observed. There were many differences observed between the alpha type and a type strains. In the alpha-type strains, there were more budding haploid cells than in the a-type. When looking at the graphs of both the cultures, we saw that the two had several similarities in the amount of cells between the a type and alpha type cultures. The outcome showed that more budding haploid cells were seen in the alpha type than in the a type. In the alpha type, there was a much bigger percentage of budding haploid cells (12.5%) than in the a type (5%). However, when looking at the graphs for the single haploid cells, the alpha type had a lower percentage than the a type. (87.5% versus 95 %) When observing the mixed culture, which was the alpha types cells over the a type cells, we expected to see lots of budding haploid cells from the a type, and also lots of single haploid cells due to the high percentages that both the alpha type and a type had when discussing the percentage total of single haploid cells. The hypothesis was correct. When looking at the mixed culture under the microscope, it was the most abundant amount of cells observed from the three types we had looked at. Yeast cells most likely commnicate using both direct contact and pheromones. The pheremones sent help yeast spot that there is a potential mate near them, which they grow towards and then create a shmoo. Then the cellular response reacts to turn the cell into a sex cell. Direct contact signaling allows the shmoos to send a signal to create a baby (zygote).

Conclusion
In this lab, the purpose was to observe cell signaling in three different types of yeast. Looking back at the results of the expirament, it appears that the alpha type yeast has more of a mating signal released than the a-type cells. This is concluded due to the much higher percentage of budding haploid cells than type a had. Our mixed culture had the most asexual reproduction activity, which shows that the different types of yeast can communicate with eachother using direct contact and pheremones.

Photosynthesis/Light Reaction Lab

Purpose

The purpose of this lab was to prove that light and chloroplasts are required for the light reactions of photosynthesis to occur.

Introduction

Photosynthesis is a way for plants to make their own food using direct sunlight. Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes. Leaves are the major locations of photosynthesis; where chloroplasts are located. In order for plants to produce sugar and release oxygen, they must first go through the light reactions. Chloroplasts split water into hydrogen and oxygen, incorporating the electrons of hydrogen. Light is then absorbed and the energy is used to drive electrons from water to generate NADPH, a stored sugar. When the electrons are excited, they burst upward and are caught by an electron accepter and then slowly released down via the electron transport chain. It is important to understand the job of the electron acceptor. DPIP can also be used instead of NADP. Every time the electrons in the chloroplast become excited, they will reduce DPIP. This will cause DPIP to change from blue to colorless. 

Methods 

Pipette 5mL of 100% dye solution into the 1st test tube, and pipette 2.5 mL of distilled water into the remaining 5 test tubes. 

Then transfer 2.5 mL of dye to the 2nd test tube and mix well. 

Transfer 2.5 mL of solution from the 2nd rest tube into the 3rd test tube and continue the process for the remaining test tubes. 

We filled a cuvette with solution from test tube 1 and read the Abs. and %T. We continued the same thing for the rest of the text tubes.

Graphs and Data

Discussion

In this lab, light and chloroplasts are proven to be needed for light reactions in photosynthesis. DPIP is used instead of NADP, which is the electron accepter in this experiment. When the electrons become excited, they will reduce the DPIP supply. These electrons come from the breaking down of light energy and water. The reduction of the DPIP supply will cause the solution to change from blue to clear. Due to the DPIP reduction, light transmittance is given off. This can be measured using a spectrophotometer, which measures the percentage of light transmittance. When the DPIP is placed in darkness, there is no reduction in it because the electrons cannot be excited because they do not have any light to excite the electrons. When the chloroplasts were boiled, it denatured the protein molecules, which also stopped reduction in the DPIP. There was a difference in percent transmittance of the unboiled chloroplasts that were in the light and the dark. This is because in the dark cuvette, there was no light, which meant that there was no light energy and therefore no breaking down of light and water which meant that the electrons could  not be excited. In the lighted cuvette, there was light energy, which aloud breaking down of light and water and therefore there were excited electrons.

Conclusion

The experiment preformed showed that chloroplasts and light are necessities for light reactions in the photosynthesis process. All in all, the outcome of the data proved this point true. It showed all factors of boiling, denaturing, and darkness, which did not allow light reactions to occur.