Cell Communication Lab

Purpose

In this experiment, we were trying to find out how yeast cells manage to communicate and thus mate asexually in order to produce offspring. In order for a message to be communicated, a signal must be sent and then received by another being; this lab will prove how yeast cells go through this communication process in order to produce a required response for the production of yeast.

Intro

Both unicellular and multicellular organisms use cell communication in order to elicit a response which helps an organism  coordinate and respond to their environment. Cellular communication can occur through direct contact, local signaling, or long-distance signaling. For a response to occur, a message much reach a receptor that is able to receive that type of message which then turns on the ability for many other reactions, or a cascade. Pheromones are a type of signaling molecule that is secreted from one organism  and detected from another organism thus providing various messages through this cellular communication and eliciting a change. 

 

As you can see above, the budding and single cells are both present on this slide. Budding cells are cells clumped together, while single cells are the ones all by themselves. Budding cells contain both a and alpha DNA, while single cells contain either one or the other.

 

Methods

In our experiment, we tested yeast reproduction. We grew yeast is two different environments: broth and a sugar like gelatin. We created three copies of each environment. One with only a type, one with only alpha type, and one with both. We then took samples and placed them under a microscope.

We then counted how many yeast were present on a sample size of our tray and recorded it into our data.

 

Data

Data was gathered by the picture taken through the microscope during the lab and counting out the cells found within that field

This table shows the number of single haploid and budding haploid cells within the alpha-type and a-type slides. As time increased, the number of budding haploids increased more than the single haploid cells. 

This is a similar chart except this one contains the the number of various cells and zygotes from the mixed culture. The budding haploid, shmoos, budding zygotes, and asci all increased after 24 hours in the incubator.

Graphs and Charts

This graph reflects the first table of the a-type and alpha-type cells 

This graphs reflects the second table above of the mixed combination of a-type and alpha-type cells

Discussion

Throughout this lab, there were a few notable differences between the A-type and Alpha-type strands of yeast while they were observed in their cultures. Over the course of the first night when stored in the incubator, the Alpha-type reproduced at a more accelerated rate than its counterpart. In addition to this, the genomes differed between both strands, yet under the microscope the behavior of each was nearly identical. In the isolated cultures, neither strand seemed to move, and no schmooz were formed. However, in the mixed culture, the pheromones from each strand were received by receptors within the plasma membrane of the opposite strand, and each strand morphed its physical structures to as to move closer to its counterpart. Schmooz can be detected by identifiying unique, irregular shapes of yeast when they are normally spherical, perfect circles.

It has become evident from this lab that yeast cells cannot communicate by direct contact, but strictly via pheromones. Yeast has no flagella or cilia to move, which is why schooz must be formed to acheive gradual movement across the dish. Pheromones are used to notify far-off yeast cells that the counterpart is present, so that they can reach each other and eventually mate. There is really no other means to communicate that other cells are nearby. Pheromones will be transduced faster if the yeast cells are closer together. For this reason, it is understandable if yeast cells that are further away take more time to respond by creating schmooz.

Conclusion

We can conclude from this lab that the most favorable environment for yeast reproduction is when there is ample food and both a type and alpha type present. This makes sense, as this is a very secure environment in which yeast can thrive. Although yeast can reproduce when there is only one reproductive type present, best results are achieved when their is a mix. It is always better to recombine DNA and increase genetic variability than to have many others have the same DNA. It leads to a higher survival rate for the species, because one genetic defect cannot wipe out the entire species.

References

http://rsob.royalsocietypublishing.org/content/3/3/130008

Carolina Cell Communication for AP Biology

Cell Cycle Video

Plant Pigments & Photosynthesis

Exercise 4A 

Purpose

In this lab, our experiment was to use chromatography paper to separate plant pigments and to measure the rate of photosynthesis in isolated chloroplasts with the use of a dye. Capillary action helps move the solvent up the chromatography in order to show us the different rates in which chlorophyll's pigments travel and are thus separated.

Introduction

Chromatography is the separation of a mixture by passing it in a solution through a medium, such as paper, in order to reveal the different rates in which the components travel at. Pigments on a chromatography paper may travel at different rates due to their solubility in the solvent. In spinach leaves, pigments that are found inside the plant are chlorophyll, xanthophyll, and carotene. While chlorophyll is the most abundant pigment in spinach as well as all plants, all of these pigments will still show up on chromatography paper.

Methods

We first crushed up a leaf, and then smeared the green die on chromatography paper. We then placed a small amount of water in a graduated cylinder and placed the paper in it, making sure to keep it suspended.

By means of capillary action, water was absorbed through the chromatography paper, spreading out the green die.

Data

This is a picture of the chromatography paper from our lab. Although we had a gaping hole at the bottom, the results still came out fine. Using the ruler, we marked off the bottom of each color.

This table shows all the measurement of each color band in millimeters and the total distance the water moved up the chromatography paper.

This table shows the Rf of the different pigments, which is the the distance pigment migrated over distance solvent front migrated.

Discussion

In chromatography, water will be absorbed vertically by means of capillary action. As noted in the provided pictures, not all of the plant pigments were carried the same distance as the water. This phenomenon occurs because not all of the pigments are equally soluble, and will therefore stop at various points on the paper. While chlorophyll a and b are really the only pigments necessary to carry out photosynthesis, carotenoids are important to absorb various wavelengths of light that will otherwise cause damage to plant cells. To focus specifically on the distance traveled by all pigments, scientists use an Rf value, which is a ratio that compares the distance migrated by the pigment to the distance traveled by the entire solvent. The Rf value could change substantially if a solvent were used that cannot be absorbed into the paper as well as water. The pigments will not change their own properties, yet they will only travel as far as the solvent will let them. As a result, it is important to use a very polar liquid (like water) for this experiment in order to see the pigments separate as much as possible.

Conclusion

From this lab we discovered that carotenoids are the most water soluble, and chlorophyll b the least soluble in water. From this, we can learn why leaves change color in the fall. After the tree cuts off water supply to the leaves, the green chlorophyll pigments break down before the yellow pigments, leaving a yellow leaf. In time, the yellow pigments break down as well.

References 

http://www.rpi.edu/dept/chem-eng/Biotech-Environ/CHROMO/chromintro.html

Exercise 4B

Purpose

In the second part of our experiment, our purpose was to study photosynthesis by measuring the transmittance of light over a certain period of time with a spectrophotometer and a dye reduction technique. Since we know wavelengths of light power photosynthesis and cause the production of ATP, we wanted to find out the different levels of transmittance during the photosynthesis process within a chloroplast (in our case, spinach) as well as prove that in order for light reactions to occur, chloroplasts and light need to be present.

Introduction

A spectrophotometer is a device that consists of two instruments: a spectrometer which produces light of any selected color/wavelength, and a photometer which measures the intensity of light. Since light is part of a continuum of radiation or energy waves, the energy that is given off from light is used to power the process of photosynthesis in chloroplasts. Dye reduction is a technique where a dye, sometimes DPIP which is a redox dye, is used to look at the change of color of the solutions or mediums in an experiment. In plants, carbon fixation is when light is absorbed by leaf pigments atmospheric carbon dioxide is converted to carbon compounds which can provide energy to produce ATP. 

Methods

We first created different environments using various chemicals, some being favorable to chloroplasts, some not. In addition, some environments were given boiled chloroplasts, some un-boiled chloroplasts, and some no chloroplasts at all. In the photo above, Judd is creating these environments. 

 

We then shined an incandescent light bulb on the different test tube environments (sparing one which used to calibrate the spectrometer.) The large jug of water was used as a heat sink, as 95% of an incandescent's energy is given off as heat. After 5 minutes, we removed the test tubes from the light as recorded their transmittance. We did the same at 10 and 15 minutes and recorded our results. 

Data

This graph shows the transmittance percentage of each cuvette from our lab. We got this data from the LoggerPro and recorded the measurement at different times.

Graphs

This graph shows the results of our data In the key, the colors correspond to the numbers and the number represent the different cuvettes. The numbers and the type of cuvette can be determined from the table above. As we can see, the cuvette with no chloroplast had no change while the unboiled/light had a great change. Unboiled/dark and boiled/light both decreased slightly.

Discussion

An important part of this lab was the use of DPIP, an electron carrier that served to replace NADP throughout the experiment. As our results will show, the presence of an electron carrier is essential in order for photosynthesis to take place at all. Five cuvettes were used in this experiment to test what ingredients are needed for plants to make sugar and survive with sunlight, water, and good soil. In the first cuvette, we added our chloroplasts but did not supply an electron carrier. Without electrons, we cannot create ATP molecules to power the Calvin Cycle, where our sugar is actually created via carbon fixation. In addition to this, the second cuvette was wrapped in film to keep out light, proving that light energy must be absorbed by the plant pigments in order to excite electrons. Our third cuvette was truly the only specimine that should have shown a high level of transmittance, because the environment had all of the necessary components to photosynthesize, reduce DPIP and essentially turn the color of the cuvette clear. In doing so, light would pass through it in the colorimeter and yield a low absorbance level when compared to the other four cuvettes. As for the fourth cuvette, we were able to prove that chloroplasts must be alive for DPIP to be reduced. Our fifth cuvette acted as another control when no chloroplasts were added at all, and this creates a serious problem for the plant if there are no reactants to power the dark reactions. With five cuvettes to test five different combinations, we were successfully able to determine a powerful recipe for plants to use when making their own food.

Conclusion

Our data was complex, but in the end, it was the tubes with the chloroplasts that absorbed the most light especially before the possible errors in calibration. This makes sense, as the chloroplasts role in a plant is to absorb light and donate electrons so the processes of photosynthesis can carry out.

References

http://www.ruf.rice.edu/~bioslabs/methods/protein/spectrophotometer.html

http://en.wikipedia.org/wiki/Dichlorophenolindophenol

Glowing Spinach

We were all confused when Mr. Filipek told us to go an make spinach glow without any direction. After playing around with the different solutions and equipments, we finally figured it out. We ripped up the spinach into tiny pieces and placed them in a funnel. We placed the funnel in a beaker and then added isopropyl alcohol into the funnel to drip through. At this point, Judd decided to get his hand dirty and rubbed the spinach and alcohol. Afterwards, we poured a little bit of the liquid into a graduated cylinder and shined a backlight through. And voila! Spinach glowed red!

When running the alcohol through the spinach leaves, we were able to extract chlorophyll into the liquid.The chlorophyll absorbs photons and takes it from its ground state and into an excited state. This raises the energy level and releases heat and fluorescence. This fluorescence is what causes the liquid to glow red with the help of a black light. 

References

http://c-lab.co.uk/default.aspx?id=9&projectid=58
Biology Book