Cool Mitosis Video

For all you youngin' who be strugglin' graspin' the stages of mitosis fear not! The four bros have made a video quickly going over each stage in a catchy tune

http://youtu.be/U1mIvhXUytw

Cool Yeast lab

The purpose of this lab was to conduct a study on cell communication. We did this by observing yeast mate and produce schmoos. Over several time intervals we observed the yeast both on a liquid base (sterile water) as well as on a dry base (dry Petri dish). These two surfaces were done to observe the effect they have on cell communication and their chemical signals. 

We labeled three test tubes as either alpha, A or mixed and put in the yeast cells respectively in each of the test tubes. Then we put two milliliters of sterile water in each test tubes to simulate wet environments. Then we added an equal amount of broth in each test tube in order to sustain their life overnight.  Then we left them in an incubator for 24 hours. After the 24 hours had elapsed we put samples of each test tube on a microscope slide and then counted the amount of yeast present.  

Below are the pictures we have taken of the yeast after 24 hours have elapsed:

Mixed (82 yeast are present)

Alpha (86)

A type (40 yeast were present)

Then we waited an additional five minutes for each of the test tubes. Below are the pictures of each test tube at the first time interval (5 minutes)

Mixed (39 were present)

Alpha (43 schmoos were present)

A type (95 schmoos were present)

Then we an additional five minutes and let the yeast culture. 

Mixed (231 schmoos were present)

Alpha (40 schmoos were present)

A type (5 schmoos were present)

 

As demonstrated by this lab, under the wet conditions, the A-type yeast alone went from 40 to 95 to 5 yeast cells. The alpha type went from 86 to 43 to 40 cells, and the culture of both A-type and alpha type cells went from 82 to 39 to 231 cells. Now in retrospect this data tells us very little because the yeast cells in each of the three cultures tended to vary up and down drastically. This error can be attributed to the fact that when we counted each yeast cell, we counted them from a field of view in the microscope, but not only were we onto always sampling the culture from the same exact place in the liquid, we also had no way of looking at the culture in the same place under the microscope. Theoretically, however, all three of the cultures should have increased in size. A type and alpha type should have reproduced asexually when separate, and when mixed, they should have reproduced sexually and moreso.

We also performed similar procedures to grow the yeast cultures under dry conditions. Three cultures were taken from the original test tubes (again A-type, alpha, and mixed) and allowed to dry onto an agar plate in a Petri dish. Then, as time progressed, we sampled the cultures and observed them under microscopes to determine how growth had occurred. Our results are pictured below.

At the beginning of the procedure, our dry cultures started out with the following numbers of cells.

Then at the first time interval, our dry cultures had the following numbers of cells.

At the last time interval, our dry cultures had these final numbers of cells.

As with the cultures grown under wet conditions, the ones grown under dry conditions should also have grown in a similar manner. That is, A-type and alpha type grow asexually when separated and sexually when together, and when they grow sexually, growth is greater than when the grow asexually.

Based on the data from both the wet and dry cultures, we can conclude that yeast cells grow best sexually under dry conditions. This can be attributed to the means by which yeast cells sexually reproduce.

For ease of description, Let's consider A-type and alpha type yeast cells to be like opposite genders, almost like male and female. Each gender releases a pheromone that physically attracts the opposite gender. It does this because it behaves as a ligand that stimulates the cell to change its chape and develop a shmoo that grows toward the location from which the opposite pheromone is coming. In order for the shmoo projection to grow out, the yeast cell must completely change its cytoskeletal structure, which reveals the true power of singalling molecules to really get work done. The shmoo is projected in the direction from which the opposite pheromone was produced, and the rest of the cell follows the projection toward the source. This allows the a and alpha type cells to grow toward each other, in order that they might sexually reproduce. Sexual reproduction is much more favorable for the yeast cells than asexual reproduction because it produces twice the amount of each type of cells. 

Bearing all this in mind, when we say that the yeast cells grow best under dry conditions, it's because the dry environment (as opposed to the liquid one) conducts these pheromones more effectively. And this kind of makes sense if we use an analogy. Colognes, perfumes, and body sprays were developed as a means to attract people. They behave in a similar manner as the yeast cells' pheromones, albeit certainly not so drastically, much to the chagrin of companies like Old Spice and Axe. If we were to spray the aerosol into an empty bucket of air and into a full bucket of water, we can probably guess that the dry bucket of air would conduct the scent better than the full, wet one.

Therefore, these yeast cells demonstrate the behavior of singalling moelecules and receptors and just how important and powerful they can be.

Cool Photosynthesis Lab

The main idea with chromotography paper is to be able to see the separation of pigments. In this case we are seeing the variety of pigments found in the chloroplast to see how it helps with photosynthesis. As seen below with the paper strip, we can see the wide variety of pigments being separated and then the pencil mark is there the solvent ends. The very bottom of the paper is a dark green color and as it progresses to the top it begins to get lighter and lighter. The dark green color can be concluded to be chloroplast-a which is the main pigment used to absorb every light except for green. That has a low Rf value compared to Carotene which has an Rf value of 1 because it flows along with the solvent. What factors can play a role in the distance travels can be based on the polarity of the pigment or even the intermolecular forces of the pigment. The more complex and stronger it in hydrogen bonds, then the harder it is to move along the strip. This concept is great to think about in term of thinking about why a plant needs off of these complex pigments in the chloroplast and how Rf and absorbance and relatively be related. It can be concluded that the lower the Rf, the higher the absorbance. The rest is to be seen in the following data and lab procedure. 

The relationship between absorbency and transmittance is important to understand photosynthesis. In order to calibrate the colorimeter we put regular tap water in a cuvette and zeroed the absorbance and transmittance values. This served as a baseline value for the rest of the solutions.  

This is a picture of the colorimeter that we used.

In order to find this relationship we put a 100% blue dye solution in cuvette and put it in a colorimeter to test the amount of light that absorbed and transmitted. 

This is a picture of the 100% blue dye solution for trial one. 

We then followed these same steps but instead of a 100% blue dye solution, we diluted it to 50%, 25%, 12.5%, 6.25%, 3.125% and again measured the absorbable and transmittance values. 

This is a data table of the values we have obtained. 

From this data table we can conclude that the values between absorbency and transmittance have an inverse relationship.

In the next part of the lab, we conducted trials with either boiled or unboiled chloroplasts (dead or living) and we controlled whether or not the solution was exposed to light or not. This was done in order to observe the effects of how changing these factors would effect the rate of photosynthesis. 

First we made five different test tubes with the following contents:

Test tube one with 1mL phosphate buffer, 4mL distilled water, and 3 drops of unboiled (alive) chloroplasts

Test tube two with 1 mL phosphate buffer, 3 mL distilled water, 1 mL DPIP, and 3 drops of unboiled (alive) chloroplasts

Test tube three with 1mL phosphate buffer, 3 mL distilled water, 1 mL DPIP, and 3 drops of unboiled (alive) chloroplasts 

Test tube four with 1 mL phosphate buffer, 3 mL distilled water, 1 mL DPIP, and 3 drops of boiled (dead) chloroplasts 

Test tube five with 1 mL phosphate buffer, 3 mL+3 drops of distilled water, and 1 mL DPIP

Then we poured the solutions into cuvettes for testing in ur colorimeter to test the change in their transmittance over time. 

Going from left to right, these are cuvettes  1 to 5 

The first cuvette was done in order to calibrate the colorimeter and set a baseline for comparison for the rest of the cuvettes. 

We exposed all the cuvettes to light using the 2 liter Erlenmeyer flask filled with water in front of a heat lamp so that heat wouldn't affect the chloroplasts, but only the light. To simulate dark reactions for cuvette two we wrapped the cuvette in aluminum foil. This prevented light from entering the cuvette. 

This is a picture of our heat lamp and Erlenmeyer flask set up. 

This is a data table of the values we have obtained. 

Unfortunately due to an error with the lab equipment, some of the data was not stored correctly and we could not retrieve it. 

However, in a later discussion of what our results should have been we found that all the cuvettes except the third one should have had steady transmittance. Cuvette three was the only one that should have increased transmittance since it had all the requirements for photosynthesis to occur. As photosynthesis progressed, DPIP would change from blue to colorless because the chloroplasts would reduce the DPIP. As DPIP changes from blue to colorless, the colorimeter perceives it as an increase in the solution's transmission of light. 

The function of DPIP in this experiment is to act as a primary electron acceptor. DPIP replaced P680 as an electron acceptor. The source of electrons for DPIP was the distilled water. 

The colorimeter measured the absorbence and transmittance of the solution in each cuvette.

The darkness doesn't allow for the light to excite the electrons so DPIP cannot be reduced and in turn cannot gain electrons. 

Boiling the chloroplasts kills them causing photosynthesis to not occur. Which means that DPIP cannot occur because there is nothing for it to accept. 

Live chloroplasts kept in the light will have photosynthesis occurring which means they give off electrons for DPIP to accept. As DPIP accepts electrons it's reduced and turns from blue to colorless, so it's transmittance increases. If there's no light, photosynthesis can't occur so there's no electrons for DPIP to accept so DPIP can't reduce which results in the color not changing, and so the transmittance doesn't change. 

The purpose of cuvette one was to serve as a calibration of the colorimeter and to tell the colorimeter what 100% transmittance looks like. 

Cuvette two deprived the chloroplasts of light. This shows us that deprivation of light hinders the rate of photosynthesis. 

Cuvette three contained all the necessary requirements for photosynthesis to occur, living chloroplasts and light. 

Cuvette four contained all the necessary requirements for photosynthesis to occur except living chloroplasts. This tells is that death of chloroplasts hinders photosynthesis. 

Cuvette five contained no chloroplasts which tells us that having no chloroplasts hinders photosynthesis.

Cuvette five specifically behaved as a double negative control to show that DPIP does not reduce on it's own. If it did reduce on its own, that that would reduce the reduction that photosynthesis contributed to DPIP. 

This labs shows us that photosynthesis occurs only when chloroplasts are alive and are exposed to light and transmittance and photosynthesis have a direct relationship.